1 ==========================
2 The Tahoe REST-ful Web API
3 ==========================
5 1. `Enabling the web-API port`_
6 2. `Basic Concepts: GET, PUT, DELETE, POST`_
11 4. `Slow Operations, Progress, and Cancelling`_
12 5. `Programmatic Operations`_
15 2. `Writing/Uploading a File`_
16 3. `Creating a New Directory`_
17 4. `Getting Information About a File Or Directory (as JSON)`_
18 5. `Attaching an Existing File or Directory by its read- or write-cap`_
19 6. `Adding Multiple Files or Directories to a Parent Directory at Once`_
20 7. `Unlinking a File or Directory`_
22 6. `Browser Operations: Human-Oriented Interfaces`_
24 1. `Viewing a Directory (as HTML)`_
25 2. `Viewing/Downloading a File`_
26 3. `Getting Information About a File Or Directory (as HTML)`_
27 4. `Creating a Directory`_
28 5. `Uploading a File`_
29 6. `Attaching an Existing File Or Directory (by URI)`_
30 7. `Unlinking a Child`_
31 8. `Renaming a Child`_
32 9. `Relinking ("Moving") a Child`_
33 10. `Other Utilities`_
34 11. `Debugging and Testing Features`_
36 7. `Other Useful Pages`_
37 8. `Static Files in /public_html`_
38 9. `Safety and Security Issues -- Names vs. URIs`_
39 10. `Concurrency Issues`_
40 11. `Access Blacklist`_
43 Enabling the web-API port
44 =========================
46 Every Tahoe node is capable of running a built-in HTTP server. To enable
47 this, just write a port number into the "[node]web.port" line of your node's
48 tahoe.cfg file. For example, writing "web.port = 3456" into the "[node]"
49 section of $NODEDIR/tahoe.cfg will cause the node to run a webserver on port
52 This string is actually a Twisted "strports" specification, meaning you can
53 get more control over the interface to which the server binds by supplying
54 additional arguments. For more details, see the documentation on
55 `twisted.application.strports
56 <https://twistedmatrix.com/documents/current/api/twisted.application.strports.html>`_.
58 Writing "tcp:3456:interface=127.0.0.1" into the web.port line does the same
59 but binds to the loopback interface, ensuring that only the programs on the
60 local host can connect. Using "ssl:3456:privateKey=mykey.pem:certKey=cert.pem"
63 This webport can be set when the node is created by passing a --webport
64 option to the 'tahoe create-node' command. By default, the node listens on
65 port 3456, on the loopback (127.0.0.1) interface.
68 Basic Concepts: GET, PUT, DELETE, POST
69 ======================================
71 As described in `docs/architecture.rst <../architecture.rst>`_, each file
72 and directory in a Tahoe virtual filesystem is referenced by an identifier
73 that combines the designation of the object with the authority to do something
74 with it (such as read or modify the contents). This identifier is called a
75 "read-cap" or "write-cap", depending upon whether it enables read-only or
76 read-write access. These "caps" are also referred to as URIs (which may be
77 confusing because they are not currently `RFC3986
78 <https://tools.ietf.org/html/rfc3986>`_-compliant URIs).
80 The Tahoe web-based API is "REST-ful", meaning it implements the concepts of
81 "REpresentational State Transfer": the original scheme by which the World
82 Wide Web was intended to work. Each object (file or directory) is referenced
83 by a URL that includes the read- or write- cap. HTTP methods (GET, PUT, and
84 DELETE) are used to manipulate these objects. You can think of the URL as a
85 noun, and the method as a verb.
87 In REST, the GET method is used to retrieve information about an object, or
88 to retrieve some representation of the object itself. When the object is a
89 file, the basic GET method will simply return the contents of that file.
90 Other variations (generally implemented by adding query parameters to the
91 URL) will return information about the object, such as metadata. GET
92 operations are required to have no side-effects.
94 PUT is used to upload new objects into the filesystem, or to replace an
95 existing link or the contents of a mutable file. DELETE is used to unlink
96 objects from directories. Both PUT and DELETE are required to be idempotent:
97 performing the same operation multiple times must have the same side-effects
98 as only performing it once.
100 POST is used for more complicated actions that cannot be expressed as a GET,
101 PUT, or DELETE. POST operations can be thought of as a method call: sending
102 some message to the object referenced by the URL. In Tahoe, POST is also used
103 for operations that must be triggered by an HTML form (including upload and
104 unlinking), because otherwise a regular web browser has no way to accomplish
105 these tasks. In general, everything that can be done with a PUT or DELETE can
106 also be done with a POST.
108 Tahoe's web API is designed for two different kinds of consumer. The first is
109 a program that needs to manipulate the virtual file system. Such programs are
110 expected to use the RESTful interface described above. The second is a human
111 using a standard web browser to work with the filesystem. This user is given
112 a series of HTML pages with links to download files, and forms that use POST
113 actions to upload, rename, and unlink files.
115 When an error occurs, the HTTP response code will be set to an appropriate
116 400-series code (like 404 Not Found for an unknown childname, or 400 Bad Request
117 when the parameters to a web-API operation are invalid), and the HTTP response
118 body will usually contain a few lines of explanation as to the cause of the
119 error and possible responses. Unusual exceptions may result in a 500 Internal
120 Server Error as a catch-all, with a default response body containing
121 a Nevow-generated HTML-ized representation of the Python exception stack trace
122 that caused the problem. CLI programs which want to copy the response body to
123 stderr should provide an "Accept: text/plain" header to their requests to get
124 a plain text stack trace instead. If the Accept header contains ``*/*``, or
125 ``text/*``, or text/html (or if there is no Accept header), HTML tracebacks will
132 Tahoe uses a variety of read- and write- caps to identify files and
133 directories. The most common of these is the "immutable file read-cap", which
134 is used for most uploaded files. These read-caps look like the following::
136 URI:CHK:ime6pvkaxuetdfah2p2f35pe54:4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a:3:10:202
138 The next most common is a "directory write-cap", which provides both read and
139 write access to a directory, and look like this::
141 URI:DIR2:djrdkfawoqihigoett4g6auz6a:jx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq
143 There are also "directory read-caps", which start with "URI:DIR2-RO:", and
144 give read-only access to a directory. Finally there are also mutable file
145 read- and write- caps, which start with "URI:SSK", and give access to mutable
148 (Later versions of Tahoe will make these strings shorter, and will remove the
149 unfortunate colons, which must be escaped when these caps are embedded in
152 To refer to any Tahoe object through the web API, you simply need to combine
153 a prefix (which indicates the HTTP server to use) with the cap (which
154 indicates which object inside that server to access). Since the default Tahoe
155 webport is 3456, the most common prefix is one that will use a local node
156 listening on this port::
158 http://127.0.0.1:3456/uri/ + $CAP
160 So, to access the directory named above (which happens to be the
161 publically-writeable sample directory on the Tahoe test grid, described at
162 http://allmydata.org/trac/tahoe-lafs/wiki/TestGrid), the URL would be::
164 http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/
166 (note that the colons in the directory-cap are url-encoded into "%3A"
169 Likewise, to access the file named above, use::
171 http://127.0.0.1:3456/uri/URI%3ACHK%3Aime6pvkaxuetdfah2p2f35pe54%3A4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a%3A3%3A10%3A202
173 In the rest of this document, we'll use "$DIRCAP" as shorthand for a read-cap
174 or write-cap that refers to a directory, and "$FILECAP" to abbreviate a cap
175 that refers to a file (whether mutable or immutable). So those URLs above can
178 http://127.0.0.1:3456/uri/$DIRCAP/
179 http://127.0.0.1:3456/uri/$FILECAP
181 The operation summaries below will abbreviate these further, by eliding the
182 server prefix. They will be displayed like this::
187 /cap can be used as a synonym for /uri. If interoperability with older web-API
188 servers is required, /uri should be used.
193 Tahoe directories contain named child entries, just like directories in a regular
194 local filesystem. These child entries, called "dirnodes", consist of a name,
195 metadata, a write slot, and a read slot. The write and read slots normally contain
196 a write-cap and read-cap referring to the same object, which can be either a file
197 or a subdirectory. The write slot may be empty (actually, both may be empty,
198 but that is unusual).
200 If you have a Tahoe URL that refers to a directory, and want to reference a
201 named child inside it, just append the child name to the URL. For example, if
202 our sample directory contains a file named "welcome.txt", we can refer to
205 http://127.0.0.1:3456/uri/$DIRCAP/welcome.txt
207 (or http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/welcome.txt)
209 Multiple levels of subdirectories can be handled this way::
211 http://127.0.0.1:3456/uri/$DIRCAP/tahoe-source/docs/architecture.rst
213 In this document, when we need to refer to a URL that references a file using
214 this child-of-some-directory format, we'll use the following string::
216 /uri/$DIRCAP/[SUBDIRS../]FILENAME
218 The "[SUBDIRS../]" part means that there are zero or more (optional)
219 subdirectory names in the middle of the URL. The "FILENAME" at the end means
220 that this whole URL refers to a file of some sort, rather than to a
223 When we need to refer specifically to a directory in this way, we'll write::
225 /uri/$DIRCAP/[SUBDIRS../]SUBDIR
228 Note that all components of pathnames in URLs are required to be UTF-8
229 encoded, so "resume.doc" (with an acute accent on both E's) would be accessed
232 http://127.0.0.1:3456/uri/$DIRCAP/r%C3%A9sum%C3%A9.doc
234 Also note that the filenames inside upload POST forms are interpreted using
235 whatever character set was provided in the conventional '_charset' field, and
236 defaults to UTF-8 if not otherwise specified. The JSON representation of each
237 directory contains native Unicode strings. Tahoe directories are specified to
238 contain Unicode filenames, and cannot contain binary strings that are not
239 representable as such.
241 All Tahoe operations that refer to existing files or directories must include
242 a suitable read- or write- cap in the URL: the web-API server won't add one
243 for you. If you don't know the cap, you can't access the file. This allows
244 the security properties of Tahoe caps to be extended across the web-API
248 Slow Operations, Progress, and Cancelling
249 =========================================
251 Certain operations can be expected to take a long time. The "t=deep-check",
252 described below, will recursively visit every file and directory reachable
253 from a given starting point, which can take minutes or even hours for
254 extremely large directory structures. A single long-running HTTP request is a
255 fragile thing: proxies, NAT boxes, browsers, and users may all grow impatient
256 with waiting and give up on the connection.
258 For this reason, long-running operations have an "operation handle", which
259 can be used to poll for status/progress messages while the operation
260 proceeds. This handle can also be used to cancel the operation. These handles
261 are created by the client, and passed in as a an "ophandle=" query argument
262 to the POST or PUT request which starts the operation. The following
263 operations can then be used to retrieve status:
265 ``GET /operations/$HANDLE?output=HTML (with or without t=status)``
267 ``GET /operations/$HANDLE?output=JSON (same)``
269 These two retrieve the current status of the given operation. Each operation
270 presents a different sort of information, but in general the page retrieved
273 * whether the operation is complete, or if it is still running
274 * how much of the operation is complete, and how much is left, if possible
276 Note that the final status output can be quite large: a deep-manifest of a
277 directory structure with 300k directories and 200k unique files is about
278 275MB of JSON, and might take two minutes to generate. For this reason, the
279 full status is not provided until the operation has completed.
281 The HTML form will include a meta-refresh tag, which will cause a regular
282 web browser to reload the status page about 60 seconds later. This tag will
283 be removed once the operation has completed.
285 There may be more status information available under
286 /operations/$HANDLE/$ETC : i.e., the handle forms the root of a URL space.
288 ``POST /operations/$HANDLE?t=cancel``
290 This terminates the operation, and returns an HTML page explaining what was
291 cancelled. If the operation handle has already expired (see below), this
292 POST will return a 404, which indicates that the operation is no longer
293 running (either it was completed or terminated). The response body will be
294 the same as a GET /operations/$HANDLE on this operation handle, and the
295 handle will be expired immediately afterwards.
297 The operation handle will eventually expire, to avoid consuming an unbounded
298 amount of memory. The handle's time-to-live can be reset at any time, by
299 passing a retain-for= argument (with a count of seconds) to either the
300 initial POST that starts the operation, or the subsequent GET request which
301 asks about the operation. For example, if a 'GET
302 /operations/$HANDLE?output=JSON&retain-for=600' query is performed, the
303 handle will remain active for 600 seconds (10 minutes) after the GET was
306 In addition, if the GET includes a release-after-complete=True argument, and
307 the operation has completed, the operation handle will be released
310 If a retain-for= argument is not used, the default handle lifetimes are:
312 * handles will remain valid at least until their operation finishes
313 * uncollected handles for finished operations (i.e. handles for
314 operations that have finished but for which the GET page has not been
315 accessed since completion) will remain valid for four days, or for
316 the total time consumed by the operation, whichever is greater.
317 * collected handles (i.e. the GET page has been retrieved at least once
318 since the operation completed) will remain valid for one day.
320 Many "slow" operations can begin to use unacceptable amounts of memory when
321 operating on large directory structures. The memory usage increases when the
322 ophandle is polled, as the results must be copied into a JSON string, sent
323 over the wire, then parsed by a client. So, as an alternative, many "slow"
324 operations have streaming equivalents. These equivalents do not use operation
325 handles. Instead, they emit line-oriented status results immediately. Client
326 code can cancel the operation by simply closing the HTTP connection.
329 Programmatic Operations
330 =======================
332 Now that we know how to build URLs that refer to files and directories in a
333 Tahoe virtual filesystem, what sorts of operations can we do with those URLs?
334 This section contains a catalog of GET, PUT, DELETE, and POST operations that
335 can be performed on these URLs. This set of operations are aimed at programs
336 that use HTTP to communicate with a Tahoe node. A later section describes
337 operations that are intended for web browsers.
343 ``GET /uri/$FILECAP``
345 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME``
347 This will retrieve the contents of the given file. The HTTP response body
348 will contain the sequence of bytes that make up the file.
350 To view files in a web browser, you may want more control over the
351 Content-Type and Content-Disposition headers. Please see the next section
352 "Browser Operations", for details on how to modify these URLs for that
356 Writing/Uploading a File
357 ------------------------
359 ``PUT /uri/$FILECAP``
361 ``PUT /uri/$DIRCAP/[SUBDIRS../]FILENAME``
363 Upload a file, using the data from the HTTP request body, and add whatever
364 child links and subdirectories are necessary to make the file available at
365 the given location. Once this operation succeeds, a GET on the same URL will
366 retrieve the same contents that were just uploaded. This will create any
367 necessary intermediate subdirectories.
369 To use the /uri/$FILECAP form, $FILECAP must be a write-cap for a mutable file.
371 In the /uri/$DIRCAP/[SUBDIRS../]FILENAME form, if the target file is a
372 writeable mutable file, that file's contents will be overwritten
373 in-place. If it is a read-cap for a mutable file, an error will occur.
374 If it is an immutable file, the old file will be discarded, and a new
375 one will be put in its place. If the target file is a writable mutable
376 file, you may also specify an "offset" parameter -- a byte offset that
377 determines where in the mutable file the data from the HTTP request
378 body is placed. This operation is relatively efficient for MDMF mutable
379 files, and is relatively inefficient (but still supported) for SDMF
380 mutable files. If no offset parameter is specified, then the entire
381 file is replaced with the data from the HTTP request body. For an
382 immutable file, the "offset" parameter is not valid.
384 When creating a new file, you can control the type of file created by
385 specifying a format= argument in the query string. format=MDMF creates an
386 MDMF mutable file. format=SDMF creates an SDMF mutable file. format=CHK
387 creates an immutable file. The value of the format argument is
388 case-insensitive. If no format is specified, the newly-created file will be
389 immutable (but see below).
391 For compatibility with previous versions of Tahoe-LAFS, the web-API will
392 also accept a mutable=true argument in the query string. If mutable=true is
393 given, then the new file will be mutable, and its format will be the default
394 mutable file format, as configured by the [client]mutable.format option of
395 tahoe.cfg on the Tahoe-LAFS node hosting the webapi server. Use of
396 mutable=true is discouraged; new code should use format= instead of
397 mutable=true (unless it needs to be compatible with web-API servers older
398 than v1.9.0). If neither format= nor mutable=true are given, the
399 newly-created file will be immutable.
401 This returns the file-cap of the resulting file. If a new file was created
402 by this method, the HTTP response code (as dictated by rfc2616) will be set
403 to 201 CREATED. If an existing file was replaced or modified, the response
406 Note that the 'curl -T localfile http://127.0.0.1:3456/uri/$DIRCAP/foo.txt'
407 command can be used to invoke this operation.
411 This uploads a file, and produces a file-cap for the contents, but does not
412 attach the file into the filesystem. No directories will be modified by
413 this operation. The file-cap is returned as the body of the HTTP response.
415 This method accepts format= and mutable=true as query string arguments, and
416 interprets those arguments in the same way as the linked forms of PUT
417 described immediately above.
419 Creating a New Directory
420 ------------------------
422 ``POST /uri?t=mkdir``
426 Create a new empty directory and return its write-cap as the HTTP response
427 body. This does not make the newly created directory visible from the
428 filesystem. The "PUT" operation is provided for backwards compatibility:
429 new code should use POST.
431 This supports a format= argument in the query string. The format=
432 argument, if specified, controls the format of the directory. format=MDMF
433 indicates that the directory should be stored as an MDMF file; format=SDMF
434 indicates that the directory should be stored as an SDMF file. The value of
435 the format= argument is case-insensitive. If no format= argument is
436 given, the directory's format is determined by the default mutable file
437 format, as configured on the Tahoe-LAFS node responding to the request.
439 ``POST /uri?t=mkdir-with-children``
441 Create a new directory, populated with a set of child nodes, and return its
442 write-cap as the HTTP response body. The new directory is not attached to
443 any other directory: the returned write-cap is the only reference to it.
445 The format of the directory can be controlled with the format= argument in
446 the query string, as described above.
448 Initial children are provided as the body of the POST form (this is more
449 efficient than doing separate mkdir and set_children operations). If the
450 body is empty, the new directory will be empty. If not empty, the body will
451 be interpreted as a UTF-8 JSON-encoded dictionary of children with which the
452 new directory should be populated, using the same format as would be
453 returned in the 'children' value of the t=json GET request, described below.
454 Each dictionary key should be a child name, and each value should be a list
455 of [TYPE, PROPDICT], where PROPDICT contains "rw_uri", "ro_uri", and
456 "metadata" keys (all others are ignored). For example, the PUT request body
460 "Fran\u00e7ais": [ "filenode", {
461 "ro_uri": "URI:CHK:...",
463 "ctime": 1202777696.7564139,
464 "mtime": 1202777696.7564139,
466 "linkcrtime": 1202777696.7564139,
467 "linkmotime": 1202777696.7564139
469 "subdir": [ "dirnode", {
470 "rw_uri": "URI:DIR2:...",
471 "ro_uri": "URI:DIR2-RO:...",
473 "ctime": 1202778102.7589991,
474 "mtime": 1202778111.2160511,
476 "linkcrtime": 1202777696.7564139,
477 "linkmotime": 1202777696.7564139
481 For forward-compatibility, a mutable directory can also contain caps in
482 a format that is unknown to the web-API server. When such caps are retrieved
483 from a mutable directory in a "ro_uri" field, they will be prefixed with
484 the string "ro.", indicating that they must not be decoded without
485 checking that they are read-only. The "ro." prefix must not be stripped
486 off without performing this check. (Future versions of the web-API server
487 will perform it where necessary.)
489 If both the "rw_uri" and "ro_uri" fields are present in a given PROPDICT,
490 and the web-API server recognizes the rw_uri as a write cap, then it will
491 reset the ro_uri to the corresponding read cap and discard the original
492 contents of ro_uri (in order to ensure that the two caps correspond to the
493 same object and that the ro_uri is in fact read-only). However this may not
494 happen for caps in a format unknown to the web-API server. Therefore, when
495 writing a directory the web-API client should ensure that the contents
496 of "rw_uri" and "ro_uri" for a given PROPDICT are a consistent
497 (write cap, read cap) pair if possible. If the web-API client only has
498 one cap and does not know whether it is a write cap or read cap, then
499 it is acceptable to set "rw_uri" to that cap and omit "ro_uri". The
500 client must not put a write cap into a "ro_uri" field.
502 The metadata may have a "no-write" field. If this is set to true in the
503 metadata of a link, it will not be possible to open that link for writing
504 via the SFTP frontend; see `<FTP-and-SFTP.rst>`_ for details.
505 Also, if the "no-write" field is set to true in the metadata of a link to
506 a mutable child, it will cause the link to be diminished to read-only.
508 Note that the web-API-using client application must not provide the
509 "Content-Type: multipart/form-data" header that usually accompanies HTML
510 form submissions, since the body is not formatted this way. Doing so will
511 cause a server error as the lower-level code misparses the request body.
513 Child file names should each be expressed as a Unicode string, then used as
514 keys of the dictionary. The dictionary should then be converted into JSON,
515 and the resulting string encoded into UTF-8. This UTF-8 bytestring should
516 then be used as the POST body.
518 ``POST /uri?t=mkdir-immutable``
520 Like t=mkdir-with-children above, but the new directory will be
521 deep-immutable. This means that the directory itself is immutable, and that
522 it can only contain objects that are treated as being deep-immutable, like
523 immutable files, literal files, and deep-immutable directories.
525 For forward-compatibility, a deep-immutable directory can also contain caps
526 in a format that is unknown to the web-API server. When such caps are retrieved
527 from a deep-immutable directory in a "ro_uri" field, they will be prefixed
528 with the string "imm.", indicating that they must not be decoded without
529 checking that they are immutable. The "imm." prefix must not be stripped
530 off without performing this check. (Future versions of the web-API server
531 will perform it where necessary.)
533 The cap for each child may be given either in the "rw_uri" or "ro_uri"
534 field of the PROPDICT (not both). If a cap is given in the "rw_uri" field,
535 then the web-API server will check that it is an immutable read-cap of a
536 *known* format, and give an error if it is not. If a cap is given in the
537 "ro_uri" field, then the web-API server will still check whether known
538 caps are immutable, but for unknown caps it will simply assume that the
539 cap can be stored, as described above. Note that an attacker would be
540 able to store any cap in an immutable directory, so this check when
541 creating the directory is only to help non-malicious clients to avoid
542 accidentally giving away more authority than intended.
544 A non-empty request body is mandatory, since after the directory is created,
545 it will not be possible to add more children to it.
547 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
549 ``PUT /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
551 Create new directories as necessary to make sure that the named target
552 ($DIRCAP/SUBDIRS../SUBDIR) is a directory. This will create additional
553 intermediate mutable directories as necessary. If the named target directory
554 already exists, this will make no changes to it.
556 If the final directory is created, it will be empty.
558 This accepts a format= argument in the query string, which controls the
559 format of the named target directory, if it does not already exist. format=
560 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
561 format= only controls the format of the named target directory;
562 intermediate directories, if created, are created based on the default
563 mutable type, as configured on the Tahoe-LAFS server responding to the
566 This operation will return an error if a blocking file is present at any of
567 the parent names, preventing the server from creating the necessary parent
568 directory; or if it would require changing an immutable directory.
570 The write-cap of the new directory will be returned as the HTTP response
573 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-with-children``
575 Like /uri?t=mkdir-with-children, but the final directory is created as a
576 child of an existing mutable directory. This will create additional
577 intermediate mutable directories as necessary. If the final directory is
578 created, it will be populated with initial children from the POST request
579 body, as described above.
581 This accepts a format= argument in the query string, which controls the
582 format of the target directory, if the target directory is created as part
583 of the operation. format= is interpreted in the same way as in the POST/
584 uri?t=mkdir-with-children operation. Note that format= only controls the
585 format of the named target directory; intermediate directories, if created,
586 are created using the default mutable type setting, as configured on the
587 Tahoe-LAFS server responding to the request.
589 This operation will return an error if a blocking file is present at any of
590 the parent names, preventing the server from creating the necessary parent
591 directory; or if it would require changing an immutable directory; or if
592 the immediate parent directory already has a a child named SUBDIR.
594 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-immutable``
596 Like /uri?t=mkdir-immutable, but the final directory is created as a child
597 of an existing mutable directory. The final directory will be deep-immutable,
598 and will be populated with the children specified as a JSON dictionary in
599 the POST request body.
601 In Tahoe 1.6 this operation creates intermediate mutable directories if
602 necessary, but that behaviour should not be relied on; see ticket #920.
604 This operation will return an error if the parent directory is immutable,
605 or already has a child named SUBDIR.
607 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME``
609 Create a new empty mutable directory and attach it to the given existing
610 directory. This will create additional intermediate directories as necessary.
612 This accepts a format= argument in the query string, which controls the
613 format of the named target directory, if it does not already exist. format=
614 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
615 format= only controls the format of the named target directory;
616 intermediate directories, if created, are created based on the default
617 mutable type, as configured on the Tahoe-LAFS server responding to the
620 This operation will return an error if a blocking file is present at any of
621 the parent names, preventing the server from creating the necessary parent
622 directory, or if it would require changing any immutable directory.
624 The URL of this operation points to the parent of the bottommost new directory,
625 whereas the /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir operation above has a URL
626 that points directly to the bottommost new directory.
628 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME``
630 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME, but the new directory will
631 be populated with initial children via the POST request body. This command
632 will create additional intermediate mutable directories as necessary.
634 This accepts a format= argument in the query string, which controls the
635 format of the target directory, if the target directory is created as part
636 of the operation. format= is interpreted in the same way as in the POST/
637 uri?t=mkdir-with-children operation. Note that format= only controls the
638 format of the named target directory; intermediate directories, if created,
639 are created using the default mutable type setting, as configured on the
640 Tahoe-LAFS server responding to the request.
642 This operation will return an error if a blocking file is present at any of
643 the parent names, preventing the server from creating the necessary parent
644 directory; or if it would require changing an immutable directory; or if
645 the immediate parent directory already has a a child named NAME.
647 Note that the name= argument must be passed as a queryarg, because the POST
648 request body is used for the initial children JSON.
650 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-immutable&name=NAME``
652 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME, but the
653 final directory will be deep-immutable. The children are specified as a
654 JSON dictionary in the POST request body. Again, the name= argument must be
655 passed as a queryarg.
657 In Tahoe 1.6 this operation creates intermediate mutable directories if
658 necessary, but that behaviour should not be relied on; see ticket #920.
660 This operation will return an error if the parent directory is immutable,
661 or already has a child named NAME.
664 Getting Information About a File Or Directory (as JSON)
665 -------------------------------------------------------
667 ``GET /uri/$FILECAP?t=json``
669 ``GET /uri/$DIRCAP?t=json``
671 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json``
673 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json``
675 This returns a machine-parseable JSON-encoded description of the given
676 object. The JSON always contains a list, and the first element of the list is
677 always a flag that indicates whether the referenced object is a file or a
678 directory. If it is a capability to a file, then the information includes
679 file size and URI, like this::
681 GET /uri/$FILECAP?t=json :
685 "verify_uri": verify_uri,
691 If it is a capability to a directory followed by a path from that directory
692 to a file, then the information also includes metadata from the link to the
693 file in the parent directory, like this::
695 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json
699 "verify_uri": verify_uri,
704 "ctime": 1202777696.7564139,
705 "mtime": 1202777696.7564139,
707 "linkcrtime": 1202777696.7564139,
708 "linkmotime": 1202777696.7564139
711 If it is a directory, then it includes information about the children of
712 this directory, as a mapping from child name to a set of data about the
713 child (the same data that would appear in a corresponding GET?t=json of the
714 child itself). The child entries also include metadata about each child,
715 including link-creation- and link-change- timestamps. The output looks like
718 GET /uri/$DIRCAP?t=json :
719 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json :
722 "rw_uri": read_write_uri,
723 "ro_uri": read_only_uri,
724 "verify_uri": verify_uri,
728 "foo.txt": [ "filenode",
733 "ctime": 1202777696.7564139,
734 "mtime": 1202777696.7564139,
736 "linkcrtime": 1202777696.7564139,
737 "linkmotime": 1202777696.7564139
739 "subdir": [ "dirnode",
744 "ctime": 1202778102.7589991,
745 "mtime": 1202778111.2160511,
747 "linkcrtime": 1202777696.7564139,
748 "linkmotime": 1202777696.7564139
752 In the above example, note how 'children' is a dictionary in which the keys
753 are child names and the values depend upon whether the child is a file or a
754 directory. The value is mostly the same as the JSON representation of the
755 child object (except that directories do not recurse -- the "children"
756 entry of the child is omitted, and the directory view includes the metadata
757 that is stored on the directory edge).
759 The rw_uri field will be present in the information about a directory
760 if and only if you have read-write access to that directory. The verify_uri
761 field will be present if and only if the object has a verify-cap
762 (non-distributed LIT files do not have verify-caps).
764 If the cap is of an unknown format, then the file size and verify_uri will
767 GET /uri/$UNKNOWNCAP?t=json :
770 "ro_uri": unknown_read_uri
773 GET /uri/$DIRCAP/[SUBDIRS../]UNKNOWNCHILDNAME?t=json :
776 "rw_uri": unknown_write_uri,
777 "ro_uri": unknown_read_uri,
780 "ctime": 1202777696.7564139,
781 "mtime": 1202777696.7564139,
783 "linkcrtime": 1202777696.7564139,
784 "linkmotime": 1202777696.7564139
787 As in the case of file nodes, the metadata will only be present when the
788 capability is to a directory followed by a path. The "mutable" field is also
789 not always present; when it is absent, the mutability of the object is not
795 The value of the 'tahoe':'linkmotime' key is updated whenever a link to a
796 child is set. The value of the 'tahoe':'linkcrtime' key is updated whenever
797 a link to a child is created -- i.e. when there was not previously a link
800 Note however, that if the edge in the Tahoe filesystem points to a mutable
801 file and the contents of that mutable file is changed, then the
802 'tahoe':'linkmotime' value on that edge will *not* be updated, since the
803 edge itself wasn't updated -- only the mutable file was.
805 The timestamps are represented as a number of seconds since the UNIX epoch
806 (1970-01-01 00:00:00 UTC), with leap seconds not being counted in the long
809 In Tahoe earlier than v1.4.0, 'mtime' and 'ctime' keys were populated
810 instead of the 'tahoe':'linkmotime' and 'tahoe':'linkcrtime' keys. Starting
811 in Tahoe v1.4.0, the 'linkmotime'/'linkcrtime' keys in the 'tahoe' sub-dict
812 are populated. However, prior to Tahoe v1.7beta, a bug caused the 'tahoe'
813 sub-dict to be deleted by web-API requests in which new metadata is
814 specified, and not to be added to existing child links that lack it.
816 From Tahoe v1.7.0 onward, the 'mtime' and 'ctime' fields are no longer
817 populated or updated (see ticket #924), except by "tahoe backup" as
818 explained below. For backward compatibility, when an existing link is
819 updated and 'tahoe':'linkcrtime' is not present in the previous metadata
820 but 'ctime' is, the old value of 'ctime' is used as the new value of
821 'tahoe':'linkcrtime'.
823 The reason we added the new fields in Tahoe v1.4.0 is that there is a
824 "set_children" API (described below) which you can use to overwrite the
825 values of the 'mtime'/'ctime' pair, and this API is used by the
826 "tahoe backup" command (in Tahoe v1.3.0 and later) to set the 'mtime' and
827 'ctime' values when backing up files from a local filesystem into the
828 Tahoe filesystem. As of Tahoe v1.4.0, the set_children API cannot be used
829 to set anything under the 'tahoe' key of the metadata dict -- if you
830 include 'tahoe' keys in your 'metadata' arguments then it will silently
833 Therefore, if the 'tahoe' sub-dict is present, you can rely on the
834 'linkcrtime' and 'linkmotime' values therein to have the semantics described
835 above. (This is assuming that only official Tahoe clients have been used to
836 write those links, and that their system clocks were set to what you expected
837 -- there is nothing preventing someone from editing their Tahoe client or
838 writing their own Tahoe client which would overwrite those values however
839 they like, and there is nothing to constrain their system clock from taking
842 When an edge is created or updated by "tahoe backup", the 'mtime' and
843 'ctime' keys on that edge are set as follows:
845 * 'mtime' is set to the timestamp read from the local filesystem for the
846 "mtime" of the local file in question, which means the last time the
847 contents of that file were changed.
849 * On Windows, 'ctime' is set to the creation timestamp for the file
850 read from the local filesystem. On other platforms, 'ctime' is set to
851 the UNIX "ctime" of the local file, which means the last time that
852 either the contents or the metadata of the local file was changed.
854 There are several ways that the 'ctime' field could be confusing:
856 1. You might be confused about whether it reflects the time of the creation
857 of a link in the Tahoe filesystem (by a version of Tahoe < v1.7.0) or a
858 timestamp copied in by "tahoe backup" from a local filesystem.
860 2. You might be confused about whether it is a copy of the file creation
861 time (if "tahoe backup" was run on a Windows system) or of the last
862 contents-or-metadata change (if "tahoe backup" was run on a different
865 3. You might be confused by the fact that changing the contents of a
866 mutable file in Tahoe doesn't have any effect on any links pointing at
867 that file in any directories, although "tahoe backup" sets the link
868 'ctime'/'mtime' to reflect timestamps about the local file corresponding
869 to the Tahoe file to which the link points.
871 4. Also, quite apart from Tahoe, you might be confused about the meaning
872 of the "ctime" in UNIX local filesystems, which people sometimes think
873 means file creation time, but which actually means, in UNIX local
874 filesystems, the most recent time that the file contents or the file
875 metadata (such as owner, permission bits, extended attributes, etc.)
876 has changed. Note that although "ctime" does not mean file creation time
877 in UNIX, links created by a version of Tahoe prior to v1.7.0, and never
878 written by "tahoe backup", will have 'ctime' set to the link creation
882 Attaching an Existing File or Directory by its read- or write-cap
883 -----------------------------------------------------------------
885 ``PUT /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
887 This attaches a child object (either a file or directory) to a specified
888 location in the virtual filesystem. The child object is referenced by its
889 read- or write- cap, as provided in the HTTP request body. This will create
890 intermediate directories as necessary.
892 This is similar to a UNIX hardlink: by referencing a previously-uploaded file
893 (or previously-created directory) instead of uploading/creating a new one,
894 you can create two references to the same object.
896 The read- or write- cap of the child is provided in the body of the HTTP
897 request, and this same cap is returned in the response body.
899 The default behavior is to overwrite any existing object at the same
900 location. To prevent this (and make the operation return an error instead
901 of overwriting), add a "replace=false" argument, as "?t=uri&replace=false".
902 With replace=false, this operation will return an HTTP 409 "Conflict" error
903 if there is already an object at the given location, rather than
904 overwriting the existing object. To allow the operation to overwrite a
905 file, but return an error when trying to overwrite a directory, use
906 "replace=only-files" (this behavior is closer to the traditional UNIX "mv"
907 command). Note that "true", "t", and "1" are all synonyms for "True", and
908 "false", "f", and "0" are synonyms for "False", and the parameter is
911 Note that this operation does not take its child cap in the form of
912 separate "rw_uri" and "ro_uri" fields. Therefore, it cannot accept a
913 child cap in a format unknown to the web-API server, unless its URI
914 starts with "ro." or "imm.". This restriction is necessary because the
915 server is not able to attenuate an unknown write cap to a read cap.
916 Unknown URIs starting with "ro." or "imm.", on the other hand, are
917 assumed to represent read caps. The client should not prefix a write
918 cap with "ro." or "imm." and pass it to this operation, since that
919 would result in granting the cap's write authority to holders of the
923 Adding Multiple Files or Directories to a Parent Directory at Once
924 ------------------------------------------------------------------
926 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set_children``
928 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set-children`` (Tahoe >= v1.6)
930 This command adds multiple children to a directory in a single operation.
931 It reads the request body and interprets it as a JSON-encoded description
932 of the child names and read/write-caps that should be added.
934 The body should be a JSON-encoded dictionary, in the same format as the
935 "children" value returned by the "GET /uri/$DIRCAP?t=json" operation
936 described above. In this format, each key is a child names, and the
937 corresponding value is a tuple of (type, childinfo). "type" is ignored, and
938 "childinfo" is a dictionary that contains "rw_uri", "ro_uri", and
939 "metadata" keys. You can take the output of "GET /uri/$DIRCAP1?t=json" and
940 use it as the input to "POST /uri/$DIRCAP2?t=set_children" to make DIR2
941 look very much like DIR1 (except for any existing children of DIR2 that
942 were not overwritten, and any existing "tahoe" metadata keys as described
945 When the set_children request contains a child name that already exists in
946 the target directory, this command defaults to overwriting that child with
947 the new value (both child cap and metadata, but if the JSON data does not
948 contain a "metadata" key, the old child's metadata is preserved). The
949 command takes a boolean "overwrite=" query argument to control this
950 behavior. If you use "?t=set_children&overwrite=false", then an attempt to
951 replace an existing child will instead cause an error.
953 Any "tahoe" key in the new child's "metadata" value is ignored. Any
954 existing "tahoe" metadata is preserved. The metadata["tahoe"] value is
955 reserved for metadata generated by the tahoe node itself. The only two keys
956 currently placed here are "linkcrtime" and "linkmotime". For details, see
957 the section above entitled "Getting Information About a File Or Directory (as
958 JSON)", in the "About the metadata" subsection.
960 Note that this command was introduced with the name "set_children", which
961 uses an underscore rather than a hyphen as other multi-word command names
962 do. The variant with a hyphen is now accepted, but clients that desire
963 backward compatibility should continue to use "set_children".
966 Unlinking a File or Directory
967 -----------------------------
969 ``DELETE /uri/$DIRCAP/[SUBDIRS../]CHILDNAME``
971 This removes the given name from its parent directory. CHILDNAME is the
972 name to be removed, and $DIRCAP/SUBDIRS.. indicates the directory that will
975 Note that this does not actually delete the file or directory that the name
976 points to from the tahoe grid -- it only unlinks the named reference from
977 this directory. If there are other names in this directory or in other
978 directories that point to the resource, then it will remain accessible
979 through those paths. Even if all names pointing to this object are removed
980 from their parent directories, then someone with possession of its read-cap
981 can continue to access the object through that cap.
983 The object will only become completely unreachable once 1: there are no
984 reachable directories that reference it, and 2: nobody is holding a read-
985 or write- cap to the object. (This behavior is very similar to the way
986 hardlinks and anonymous files work in traditional UNIX filesystems).
988 This operation will not modify more than a single directory. Intermediate
989 directories which were implicitly created by PUT or POST methods will *not*
990 be automatically removed by DELETE.
992 This method returns the file- or directory- cap of the object that was just
996 Browser Operations: Human-oriented interfaces
997 =============================================
999 This section describes the HTTP operations that provide support for humans
1000 running a web browser. Most of these operations use HTML forms that use POST
1001 to drive the Tahoe node. This section is intended for HTML authors who want
1002 to write web pages that contain forms and buttons which manipulate the Tahoe
1005 Note that for all POST operations, the arguments listed can be provided
1006 either as URL query arguments or as form body fields. URL query arguments are
1007 separated from the main URL by "?", and from each other by "&". For example,
1008 "POST /uri/$DIRCAP?t=upload&mutable=true". Form body fields are usually
1009 specified by using <input type="hidden"> elements. For clarity, the
1010 descriptions below display the most significant arguments as URL query args.
1013 Viewing a Directory (as HTML)
1014 -----------------------------
1016 ``GET /uri/$DIRCAP/[SUBDIRS../]``
1018 This returns an HTML page, intended to be displayed to a human by a web
1019 browser, which contains HREF links to all files and directories reachable
1020 from this directory. These HREF links do not have a t= argument, meaning
1021 that a human who follows them will get pages also meant for a human. It also
1022 contains forms to upload new files, and to unlink files and directories
1023 from their parent directory. Those forms use POST methods to do their job.
1026 Viewing/Downloading a File
1027 --------------------------
1029 ``GET /uri/$FILECAP``
1031 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME``
1033 This will retrieve the contents of the given file. The HTTP response body
1034 will contain the sequence of bytes that make up the file.
1036 If you want the HTTP response to include a useful Content-Type header,
1037 either use the second form (which starts with a $DIRCAP), or add a
1038 "filename=foo" query argument, like "GET /uri/$FILECAP?filename=foo.jpg".
1039 The bare "GET /uri/$FILECAP" does not give the Tahoe node enough information
1040 to determine a Content-Type (since Tahoe immutable files are merely
1041 sequences of bytes, not typed+named file objects).
1043 If the URL has both filename= and "save=true" in the query arguments, then
1044 the server to add a "Content-Disposition: attachment" header, along with a
1045 filename= parameter. When a user clicks on such a link, most browsers will
1046 offer to let the user save the file instead of displaying it inline (indeed,
1047 most browsers will refuse to display it inline). "true", "t", "1", and other
1048 case-insensitive equivalents are all treated the same.
1050 Character-set handling in URLs and HTTP headers is a dubious art [1]_. For
1051 maximum compatibility, Tahoe simply copies the bytes from the filename=
1052 argument into the Content-Disposition header's filename= parameter, without
1053 trying to interpret them in any particular way.
1056 ``GET /named/$FILECAP/FILENAME``
1058 This is an alternate download form which makes it easier to get the correct
1059 filename. The Tahoe server will provide the contents of the given file, with
1060 a Content-Type header derived from the given filename. This form is used to
1061 get browsers to use the "Save Link As" feature correctly, and also helps
1062 command-line tools like "wget" and "curl" use the right filename. Note that
1063 this form can *only* be used with file caps; it is an error to use a
1064 directory cap after the /named/ prefix.
1066 URLs may also use /file/$FILECAP/FILENAME as a synonym for
1067 /named/$FILECAP/FILENAME.
1069 Getting Information About a File Or Directory (as HTML)
1070 -------------------------------------------------------
1072 ``GET /uri/$FILECAP?t=info``
1074 ``GET /uri/$DIRCAP/?t=info``
1076 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR/?t=info``
1078 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=info``
1080 This returns a human-oriented HTML page with more detail about the selected
1081 file or directory object. This page contains the following items:
1085 * JSON representation
1086 * raw contents (text/plain)
1087 * access caps (URIs): verify-cap, read-cap, write-cap (for mutable objects)
1088 * check/verify/repair form
1089 * deep-check/deep-size/deep-stats/manifest (for directories)
1090 * replace-contents form (for mutable files)
1093 Creating a Directory
1094 --------------------
1096 ``POST /uri?t=mkdir``
1098 This creates a new empty directory, but does not attach it to the virtual
1101 If a "redirect_to_result=true" argument is provided, then the HTTP response
1102 will cause the web browser to be redirected to a /uri/$DIRCAP page that
1103 gives access to the newly-created directory. If you bookmark this page,
1104 you'll be able to get back to the directory again in the future. This is the
1105 recommended way to start working with a Tahoe server: create a new unlinked
1106 directory (using redirect_to_result=true), then bookmark the resulting
1107 /uri/$DIRCAP page. There is a "create directory" button on the Welcome page
1108 to invoke this action.
1110 This accepts a format= argument in the query string. Refer to the
1111 documentation of the PUT /uri?t=mkdir operation in `Creating A
1112 New Directory`_ for information on the behavior of the format= argument.
1114 If "redirect_to_result=true" is not provided (or is given a value of
1115 "false"), then the HTTP response body will simply be the write-cap of the
1118 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME``
1120 This creates a new empty directory as a child of the designated SUBDIR. This
1121 will create additional intermediate directories as necessary.
1123 This accepts a format= argument in the query string. Refer to the
1124 documentation of POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME in
1125 `Creating a New Directory`_ for information on the behavior of the format=
1128 If a "when_done=URL" argument is provided, the HTTP response will cause the
1129 web browser to redirect to the given URL. This provides a convenient way to
1130 return the browser to the directory that was just modified. Without a
1131 when_done= argument, the HTTP response will simply contain the write-cap of
1132 the directory that was just created.
1138 ``POST /uri?t=upload``
1140 This uploads a file, and produces a file-cap for the contents, but does not
1141 attach the file into the filesystem. No directories will be modified by
1144 The file must be provided as the "file" field of an HTML encoded form body,
1145 produced in response to an HTML form like this::
1147 <form action="/uri" method="POST" enctype="multipart/form-data">
1148 <input type="hidden" name="t" value="upload" />
1149 <input type="file" name="file" />
1150 <input type="submit" value="Upload Unlinked" />
1153 If a "when_done=URL" argument is provided, the response body will cause the
1154 browser to redirect to the given URL. If the when_done= URL has the string
1155 "%(uri)s" in it, that string will be replaced by a URL-escaped form of the
1156 newly created file-cap. (Note that without this substitution, there is no
1157 way to access the file that was just uploaded).
1159 The default (in the absence of when_done=) is to return an HTML page that
1160 describes the results of the upload. This page will contain information
1161 about which storage servers were used for the upload, how long each
1162 operation took, etc.
1164 This accepts format= and mutable=true query string arguments. Refer to
1165 `Writing/Uploading a File`_ for information on the behavior of format= and
1168 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=upload``
1170 This uploads a file, and attaches it as a new child of the given directory,
1171 which must be mutable. The file must be provided as the "file" field of an
1172 HTML-encoded form body, produced in response to an HTML form like this::
1174 <form action="." method="POST" enctype="multipart/form-data">
1175 <input type="hidden" name="t" value="upload" />
1176 <input type="file" name="file" />
1177 <input type="submit" value="Upload" />
1180 A "name=" argument can be provided to specify the new child's name,
1181 otherwise it will be taken from the "filename" field of the upload form
1182 (most web browsers will copy the last component of the original file's
1183 pathname into this field). To avoid confusion, name= is not allowed to
1186 If there is already a child with that name, and it is a mutable file, then
1187 its contents are replaced with the data being uploaded. If it is not a
1188 mutable file, the default behavior is to remove the existing child before
1189 creating a new one. To prevent this (and make the operation return an error
1190 instead of overwriting the old child), add a "replace=false" argument, as
1191 "?t=upload&replace=false". With replace=false, this operation will return an
1192 HTTP 409 "Conflict" error if there is already an object at the given
1193 location, rather than overwriting the existing object. Note that "true",
1194 "t", and "1" are all synonyms for "True", and "false", "f", and "0" are
1195 synonyms for "False". the parameter is case-insensitive.
1197 This will create additional intermediate directories as necessary, although
1198 since it is expected to be triggered by a form that was retrieved by "GET
1199 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1202 This accepts format= and mutable=true query string arguments. Refer to
1203 `Writing/Uploading a File`_ for information on the behavior of format= and
1206 If a "when_done=URL" argument is provided, the HTTP response will cause the
1207 web browser to redirect to the given URL. This provides a convenient way to
1208 return the browser to the directory that was just modified. Without a
1209 when_done= argument, the HTTP response will simply contain the file-cap of
1210 the file that was just uploaded (a write-cap for mutable files, or a
1211 read-cap for immutable files).
1213 ``POST /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=upload``
1215 This also uploads a file and attaches it as a new child of the given
1216 directory, which must be mutable. It is a slight variant of the previous
1217 operation, as the URL refers to the target file rather than the parent
1218 directory. It is otherwise identical: this accepts mutable= and when_done=
1221 ``POST /uri/$FILECAP?t=upload``
1223 This modifies the contents of an existing mutable file in-place. An error is
1224 signalled if $FILECAP does not refer to a mutable file. It behaves just like
1225 the "PUT /uri/$FILECAP" form, but uses a POST for the benefit of HTML forms
1229 Attaching An Existing File Or Directory (by URI)
1230 ------------------------------------------------
1232 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=uri&name=CHILDNAME&uri=CHILDCAP``
1234 This attaches a given read- or write- cap "CHILDCAP" to the designated
1235 directory, with a specified child name. This behaves much like the PUT t=uri
1236 operation, and is a lot like a UNIX hardlink. It is subject to the same
1237 restrictions as that operation on the use of cap formats unknown to the
1240 This will create additional intermediate directories as necessary, although
1241 since it is expected to be triggered by a form that was retrieved by "GET
1242 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1245 This accepts the same replace= argument as POST t=upload.
1251 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=delete&name=CHILDNAME``
1253 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=unlink&name=CHILDNAME``
1255 This instructs the node to remove a child object (file or subdirectory) from
1256 the given directory, which must be mutable. Note that the entire subtree is
1257 unlinked from the parent. Unlike deleting a subdirectory in a UNIX local
1258 filesystem, the subtree need not be empty; if it isn't, then other references
1259 into the subtree will see that the child subdirectories are not modified by
1260 this operation. Only the link from the given directory to its child is severed.
1262 In Tahoe-LAFS v1.9.0 and later, t=unlink can be used as a synonym for t=delete.
1263 If interoperability with older web-API servers is required, t=delete should
1270 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=rename&from_name=OLD&to_name=NEW``
1272 This instructs the node to rename a child of the given directory, which must
1273 be mutable. This has a similar effect to removing the child, then adding the
1274 same child-cap under the new name, except that it preserves metadata. This
1275 operation cannot move the child to a different directory.
1277 The default behavior is to overwrite any existing link at the destination
1278 (replace=true). To prevent this (and make the operation return an error
1279 instead of overwriting), add a "replace=false" argument. With replace=false,
1280 this operation will return an HTTP 409 "Conflict" error if the destination
1281 is not the same link as the source and there is already a link at the
1282 destination, rather than overwriting the existing link. To allow the
1283 operation to overwrite a link to a file, but return an HTTP 409 error when
1284 trying to overwrite a link to a directory, use "replace=only-files" (this
1285 behavior is closer to the traditional UNIX "mv" command). Note that "true",
1286 "t", and "1" are all synonyms for "True"; "false", "f", and "0" are synonyms
1287 for "False"; and the parameter is case-insensitive.
1290 Relinking ("Moving") a Child
1291 ----------------------------
1293 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=relink&from_name=OLD&to_dir=$NEWDIRCAP/[NEWSUBDIRS../]&to_name=NEW``
1294 ``[&replace=true|false|only-files]`` (Tahoe >= v1.10)
1296 This instructs the node to move a child of the given source directory, into
1297 a different directory and/or to a different name. The command is named
1298 ``relink`` because what it does is add a new link to the child from the new
1299 location, then remove the old link. Nothing is actually "moved" — the child
1300 is still reachable through any path from which it was formerly reachable,
1301 and the storage space occupied by its ciphertext is not affected.
1303 The source and destination directories must be writeable. If {{{to_dir}}} is
1304 not present, the child link is renamed within the same directory. If
1305 {{{to_name}}} is not present then it defaults to {{{from_name}}}. If the
1306 destination link (directory and name) is the same as the source link, the
1307 operation has no effect.
1309 Metadata from the source directory entry is preserved. Multiple levels of
1310 descent in the source and destination paths are supported.
1312 This operation will return an HTTP 404 "Not Found" error if
1313 ``$DIRCAP/[SUBDIRS../]``, the child being moved, or the destination
1314 directory does not exist. It will return an HTTP 400 "Bad Request" error
1315 if any entry in the source or destination paths is not a directory.
1317 The default behavior is to overwrite any existing link at the destination
1318 (replace=true). To prevent this (and make the operation return an error
1319 instead of overwriting), add a "replace=false" argument. With replace=false,
1320 this operation will return an HTTP 409 "Conflict" error if the destination
1321 is not the same link as the source and there is already a link at the
1322 destination, rather than overwriting the existing link. To allow the
1323 operation to overwrite a link to a file, but return an HTTP 409 error when
1324 trying to overwrite a link to a directory, use "replace=only-files" (this
1325 behavior is closer to the traditional UNIX "mv" command). Note that "true",
1326 "t", and "1" are all synonyms for "True"; "false", "f", and "0" are synonyms
1327 for "False"; and the parameter is case-insensitive.
1329 When relinking into a different directory, for safety, the child link is
1330 not removed from the old directory until it has been successfully added to
1331 the new directory. This implies that in case of a crash or failure, the
1332 link to the child will not be lost, but it could be linked at both the old
1335 The source link should not be the same as any link (directory and child name)
1336 in the ``to_dir`` path. This restriction is not enforced, but it may be
1337 enforced in a future version. If it were violated then the result would be
1338 to create a cycle in the directory structure that is not necessarily reachable
1339 from the root of the destination path (``$NEWDIRCAP``), which could result in
1340 data loss, as described in ticket `#943`_.
1342 .. _`#943`: https://tahoe-lafs.org/trac/tahoe-lafs/ticket/943
1348 ``GET /uri?uri=$CAP``
1350 This causes a redirect to /uri/$CAP, and retains any additional query
1351 arguments (like filename= or save=). This is for the convenience of web
1352 forms which allow the user to paste in a read- or write- cap (obtained
1353 through some out-of-band channel, like IM or email).
1355 Note that this form merely redirects to the specific file or directory
1356 indicated by the $CAP: unlike the GET /uri/$DIRCAP form, you cannot
1357 traverse to children by appending additional path segments to the URL.
1359 ``GET /uri/$DIRCAP/[SUBDIRS../]?t=rename-form&name=$CHILDNAME``
1361 This provides a useful facility to browser-based user interfaces. It
1362 returns a page containing a form targetting the "POST $DIRCAP t=rename"
1363 functionality described above, with the provided $CHILDNAME present in the
1364 'from_name' field of that form. I.e. this presents a form offering to
1365 rename $CHILDNAME, requesting the new name, and submitting POST rename.
1366 This same URL format can also be used with "move-form" with the expected
1369 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
1371 This returns the file- or directory- cap for the specified object.
1373 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=readonly-uri``
1375 This returns a read-only file- or directory- cap for the specified object.
1376 If the object is an immutable file, this will return the same value as
1380 Debugging and Testing Features
1381 ------------------------------
1383 These URLs are less-likely to be helpful to the casual Tahoe user, and are
1384 mainly intended for developers.
1386 ``POST $URL?t=check``
1388 This triggers the FileChecker to determine the current "health" of the
1389 given file or directory, by counting how many shares are available. The
1390 page that is returned will display the results. This can be used as a "show
1391 me detailed information about this file" page.
1393 If a verify=true argument is provided, the node will perform a more
1394 intensive check, downloading and verifying every single bit of every share.
1396 If an add-lease=true argument is provided, the node will also add (or
1397 renew) a lease to every share it encounters. Each lease will keep the share
1398 alive for a certain period of time (one month by default). Once the last
1399 lease expires or is explicitly cancelled, the storage server is allowed to
1402 If an output=JSON argument is provided, the response will be
1403 machine-readable JSON instead of human-oriented HTML. The data is a
1404 dictionary with the following keys::
1406 storage-index: a base32-encoded string with the objects's storage index,
1407 or an empty string for LIT files
1408 summary: a string, with a one-line summary of the stats of the file
1409 results: a dictionary that describes the state of the file. For LIT files,
1410 this dictionary has only the 'healthy' key, which will always be
1411 True. For distributed files, this dictionary has the following
1413 count-shares-good: the number of good shares that were found
1414 count-shares-needed: 'k', the number of shares required for recovery
1415 count-shares-expected: 'N', the number of total shares generated
1416 count-good-share-hosts: the number of distinct storage servers with good
1418 count-wrong-shares: for mutable files, the number of shares for
1419 versions other than the 'best' one (highest
1420 sequence number, highest roothash). These are
1422 count-recoverable-versions: for mutable files, the number of
1423 recoverable versions of the file. For
1424 a healthy file, this will equal 1.
1425 count-unrecoverable-versions: for mutable files, the number of
1426 unrecoverable versions of the file.
1427 For a healthy file, this will be 0.
1428 count-corrupt-shares: the number of shares with integrity failures
1429 list-corrupt-shares: a list of "share locators", one for each share
1430 that was found to be corrupt. Each share locator
1431 is a list of (serverid, storage_index, sharenum).
1432 needs-rebalancing: (bool) True if there are multiple shares on a single
1433 storage server, indicating a reduction in reliability
1434 that could be resolved by moving shares to new
1436 servers-responding: list of base32-encoded storage server identifiers,
1437 one for each server which responded to the share
1439 healthy: (bool) True if the file is completely healthy, False otherwise.
1440 Healthy files have at least N good shares. Overlapping shares
1441 do not currently cause a file to be marked unhealthy. If there
1442 are at least N good shares, then corrupt shares do not cause the
1443 file to be marked unhealthy, although the corrupt shares will be
1444 listed in the results (list-corrupt-shares) and should be manually
1445 removed to wasting time in subsequent downloads (as the
1446 downloader rediscovers the corruption and uses alternate shares).
1447 Future compatibility: the meaning of this field may change to
1448 reflect whether the servers-of-happiness criterion is met
1450 sharemap: dict mapping share identifier to list of serverids
1451 (base32-encoded strings). This indicates which servers are
1452 holding which shares. For immutable files, the shareid is
1453 an integer (the share number, from 0 to N-1). For
1454 immutable files, it is a string of the form
1455 'seq%d-%s-sh%d', containing the sequence number, the
1456 roothash, and the share number.
1458 ``POST $URL?t=start-deep-check`` (must add &ophandle=XYZ)
1460 This initiates a recursive walk of all files and directories reachable from
1461 the target, performing a check on each one just like t=check. The result
1462 page will contain a summary of the results, including details on any
1463 file/directory that was not fully healthy.
1465 t=start-deep-check can only be invoked on a directory. An error (400
1466 BAD_REQUEST) will be signalled if it is invoked on a file. The recursive
1467 walker will deal with loops safely.
1469 This accepts the same verify= and add-lease= arguments as t=check.
1471 Since this operation can take a long time (perhaps a second per object),
1472 the ophandle= argument is required (see "Slow Operations, Progress, and
1473 Cancelling" above). The response to this POST will be a redirect to the
1474 corresponding /operations/$HANDLE page (with output=HTML or output=JSON to
1475 match the output= argument given to the POST). The deep-check operation
1476 will continue to run in the background, and the /operations page should be
1477 used to find out when the operation is done.
1479 Detailed check results for non-healthy files and directories will be
1480 available under /operations/$HANDLE/$STORAGEINDEX, and the HTML status will
1481 contain links to these detailed results.
1483 The HTML /operations/$HANDLE page for incomplete operations will contain a
1484 meta-refresh tag, set to 60 seconds, so that a browser which uses
1485 deep-check will automatically poll until the operation has completed.
1487 The JSON page (/options/$HANDLE?output=JSON) will contain a
1488 machine-readable JSON dictionary with the following keys::
1490 finished: a boolean, True if the operation is complete, else False. Some
1491 of the remaining keys may not be present until the operation
1493 root-storage-index: a base32-encoded string with the storage index of the
1494 starting point of the deep-check operation
1495 count-objects-checked: count of how many objects were checked. Note that
1496 non-distributed objects (i.e. small immutable LIT
1497 files) are not checked, since for these objects,
1498 the data is contained entirely in the URI.
1499 count-objects-healthy: how many of those objects were completely healthy
1500 count-objects-unhealthy: how many were damaged in some way
1501 count-corrupt-shares: how many shares were found to have corruption,
1502 summed over all objects examined
1503 list-corrupt-shares: a list of "share identifiers", one for each share
1504 that was found to be corrupt. Each share identifier
1505 is a list of (serverid, storage_index, sharenum).
1506 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1507 each file that was not fully healthy. 'pathname' is
1508 a list of strings (which can be joined by "/"
1509 characters to turn it into a single string),
1510 relative to the directory on which deep-check was
1511 invoked. The 'check-results' field is the same as
1512 that returned by t=check&output=JSON, described
1514 stats: a dictionary with the same keys as the t=start-deep-stats command
1517 ``POST $URL?t=stream-deep-check``
1519 This initiates a recursive walk of all files and directories reachable from
1520 the target, performing a check on each one just like t=check. For each
1521 unique object (duplicates are skipped), a single line of JSON is emitted to
1522 the HTTP response channel (or an error indication, see below). When the walk
1523 is complete, a final line of JSON is emitted which contains the accumulated
1524 file-size/count "deep-stats" data.
1526 This command takes the same arguments as t=start-deep-check.
1528 A CLI tool can split the response stream on newlines into "response units",
1529 and parse each response unit as JSON. Each such parsed unit will be a
1530 dictionary, and will contain at least the "type" key: a string, one of
1531 "file", "directory", or "stats".
1533 For all units that have a type of "file" or "directory", the dictionary will
1534 contain the following keys::
1536 "path": a list of strings, with the path that is traversed to reach the
1538 "cap": a write-cap URI for the file or directory, if available, else a
1540 "verifycap": a verify-cap URI for the file or directory
1541 "repaircap": an URI for the weakest cap that can still be used to repair
1543 "storage-index": a base32 storage index for the object
1544 "check-results": a copy of the dictionary which would be returned by
1545 t=check&output=json, with three top-level keys:
1546 "storage-index", "summary", and "results", and a variety
1547 of counts and sharemaps in the "results" value.
1549 Note that non-distributed files (i.e. LIT files) will have values of None
1550 for verifycap, repaircap, and storage-index, since these files can neither
1551 be verified nor repaired, and are not stored on the storage servers.
1552 Likewise the check-results dictionary will be limited: an empty string for
1553 storage-index, and a results dictionary with only the "healthy" key.
1555 The last unit in the stream will have a type of "stats", and will contain
1556 the keys described in the "start-deep-stats" operation, below.
1558 If any errors occur during the traversal (specifically if a directory is
1559 unrecoverable, such that further traversal is not possible), an error
1560 indication is written to the response body, instead of the usual line of
1561 JSON. This error indication line will begin with the string "ERROR:" (in all
1562 caps), and contain a summary of the error on the rest of the line. The
1563 remaining lines of the response body will be a python exception. The client
1564 application should look for the ERROR: and stop processing JSON as soon as
1565 it is seen. Note that neither a file being unrecoverable nor a directory
1566 merely being unhealthy will cause traversal to stop. The line just before
1567 the ERROR: will describe the directory that was untraversable, since the
1568 unit is emitted to the HTTP response body before the child is traversed.
1571 ``POST $URL?t=check&repair=true``
1573 This performs a health check of the given file or directory, and if the
1574 checker determines that the object is not healthy (some shares are missing
1575 or corrupted), it will perform a "repair". During repair, any missing
1576 shares will be regenerated and uploaded to new servers.
1578 This accepts the same verify=true and add-lease= arguments as t=check. When
1579 an output=JSON argument is provided, the machine-readable JSON response
1580 will contain the following keys::
1582 storage-index: a base32-encoded string with the objects's storage index,
1583 or an empty string for LIT files
1584 repair-attempted: (bool) True if repair was attempted
1585 repair-successful: (bool) True if repair was attempted and the file was
1586 fully healthy afterwards. False if no repair was
1587 attempted, or if a repair attempt failed.
1588 pre-repair-results: a dictionary that describes the state of the file
1589 before any repair was performed. This contains exactly
1590 the same keys as the 'results' value of the t=check
1591 response, described above.
1592 post-repair-results: a dictionary that describes the state of the file
1593 after any repair was performed. If no repair was
1594 performed, post-repair-results and pre-repair-results
1595 will be the same. This contains exactly the same keys
1596 as the 'results' value of the t=check response,
1599 ``POST $URL?t=start-deep-check&repair=true`` (must add &ophandle=XYZ)
1601 This triggers a recursive walk of all files and directories, performing a
1602 t=check&repair=true on each one.
1604 Like t=start-deep-check without the repair= argument, this can only be
1605 invoked on a directory. An error (400 BAD_REQUEST) will be signalled if it
1606 is invoked on a file. The recursive walker will deal with loops safely.
1608 This accepts the same verify= and add-lease= arguments as
1609 t=start-deep-check. It uses the same ophandle= mechanism as
1610 start-deep-check. When an output=JSON argument is provided, the response
1611 will contain the following keys::
1613 finished: (bool) True if the operation has completed, else False
1614 root-storage-index: a base32-encoded string with the storage index of the
1615 starting point of the deep-check operation
1616 count-objects-checked: count of how many objects were checked
1618 count-objects-healthy-pre-repair: how many of those objects were completely
1619 healthy, before any repair
1620 count-objects-unhealthy-pre-repair: how many were damaged in some way
1621 count-objects-healthy-post-repair: how many of those objects were completely
1622 healthy, after any repair
1623 count-objects-unhealthy-post-repair: how many were damaged in some way
1625 count-repairs-attempted: repairs were attempted on this many objects.
1626 count-repairs-successful: how many repairs resulted in healthy objects
1627 count-repairs-unsuccessful: how many repairs resulted did not results in
1628 completely healthy objects
1629 count-corrupt-shares-pre-repair: how many shares were found to have
1630 corruption, summed over all objects
1631 examined, before any repair
1632 count-corrupt-shares-post-repair: how many shares were found to have
1633 corruption, summed over all objects
1634 examined, after any repair
1635 list-corrupt-shares: a list of "share identifiers", one for each share
1636 that was found to be corrupt (before any repair).
1637 Each share identifier is a list of (serverid,
1638 storage_index, sharenum).
1639 list-remaining-corrupt-shares: like list-corrupt-shares, but mutable shares
1640 that were successfully repaired are not
1641 included. These are shares that need
1642 manual processing. Since immutable shares
1643 cannot be modified by clients, all corruption
1644 in immutable shares will be listed here.
1645 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1646 each file that was not fully healthy. 'pathname' is
1647 relative to the directory on which deep-check was
1648 invoked. The 'check-results' field is the same as
1649 that returned by t=check&repair=true&output=JSON,
1651 stats: a dictionary with the same keys as the t=start-deep-stats command
1654 ``POST $URL?t=stream-deep-check&repair=true``
1656 This triggers a recursive walk of all files and directories, performing a
1657 t=check&repair=true on each one. For each unique object (duplicates are
1658 skipped), a single line of JSON is emitted to the HTTP response channel (or
1659 an error indication). When the walk is complete, a final line of JSON is
1660 emitted which contains the accumulated file-size/count "deep-stats" data.
1662 This emits the same data as t=stream-deep-check (without the repair=true),
1663 except that the "check-results" field is replaced with a
1664 "check-and-repair-results" field, which contains the keys returned by
1665 t=check&repair=true&output=json (i.e. repair-attempted, repair-successful,
1666 pre-repair-results, and post-repair-results). The output does not contain
1667 the summary dictionary that is provied by t=start-deep-check&repair=true
1668 (the one with count-objects-checked and list-unhealthy-files), since the
1669 receiving client is expected to calculate those values itself from the
1670 stream of per-object check-and-repair-results.
1672 Note that the "ERROR:" indication will only be emitted if traversal stops,
1673 which will only occur if an unrecoverable directory is encountered. If a
1674 file or directory repair fails, the traversal will continue, and the repair
1675 failure will be indicated in the JSON data (in the "repair-successful" key).
1677 ``POST $DIRURL?t=start-manifest`` (must add &ophandle=XYZ)
1679 This operation generates a "manfest" of the given directory tree, mostly
1680 for debugging. This is a table of (path, filecap/dircap), for every object
1681 reachable from the starting directory. The path will be slash-joined, and
1682 the filecap/dircap will contain a link to the object in question. This page
1683 gives immediate access to every object in the virtual filesystem subtree.
1685 This operation uses the same ophandle= mechanism as deep-check. The
1686 corresponding /operations/$HANDLE page has three different forms. The
1687 default is output=HTML.
1689 If output=text is added to the query args, the results will be a text/plain
1690 list. The first line is special: it is either "finished: yes" or "finished:
1691 no"; if the operation is not finished, you must periodically reload the
1692 page until it completes. The rest of the results are a plaintext list, with
1693 one file/dir per line, slash-separated, with the filecap/dircap separated
1696 If output=JSON is added to the queryargs, then the results will be a
1697 JSON-formatted dictionary with six keys. Note that because large directory
1698 structures can result in very large JSON results, the full results will not
1699 be available until the operation is complete (i.e. until output["finished"]
1702 finished (bool): if False then you must reload the page until True
1703 origin_si (base32 str): the storage index of the starting point
1704 manifest: list of (path, cap) tuples, where path is a list of strings.
1705 verifycaps: list of (printable) verify cap strings
1706 storage-index: list of (base32) storage index strings
1707 stats: a dictionary with the same keys as the t=start-deep-stats command
1710 ``POST $DIRURL?t=start-deep-size`` (must add &ophandle=XYZ)
1712 This operation generates a number (in bytes) containing the sum of the
1713 filesize of all directories and immutable files reachable from the given
1714 directory. This is a rough lower bound of the total space consumed by this
1715 subtree. It does not include space consumed by mutable files, nor does it
1716 take expansion or encoding overhead into account. Later versions of the
1717 code may improve this estimate upwards.
1719 The /operations/$HANDLE status output consists of two lines of text::
1724 ``POST $DIRURL?t=start-deep-stats`` (must add &ophandle=XYZ)
1726 This operation performs a recursive walk of all files and directories
1727 reachable from the given directory, and generates a collection of
1728 statistics about those objects.
1730 The result (obtained from the /operations/$OPHANDLE page) is a
1731 JSON-serialized dictionary with the following keys (note that some of these
1732 keys may be missing until 'finished' is True)::
1734 finished: (bool) True if the operation has finished, else False
1735 count-immutable-files: count of how many CHK files are in the set
1736 count-mutable-files: same, for mutable files (does not include directories)
1737 count-literal-files: same, for LIT files (data contained inside the URI)
1738 count-files: sum of the above three
1739 count-directories: count of directories
1740 count-unknown: count of unrecognized objects (perhaps from the future)
1741 size-immutable-files: total bytes for all CHK files in the set, =deep-size
1742 size-mutable-files (TODO): same, for current version of all mutable files
1743 size-literal-files: same, for LIT files
1744 size-directories: size of directories (includes size-literal-files)
1745 size-files-histogram: list of (minsize, maxsize, count) buckets,
1746 with a histogram of filesizes, 5dB/bucket,
1747 for both literal and immutable files
1748 largest-directory: number of children in the largest directory
1749 largest-immutable-file: number of bytes in the largest CHK file
1751 size-mutable-files is not implemented, because it would require extra
1752 queries to each mutable file to get their size. This may be implemented in
1755 Assuming no sharing, the basic space consumed by a single root directory is
1756 the sum of size-immutable-files, size-mutable-files, and size-directories.
1757 The actual disk space used by the shares is larger, because of the
1758 following sources of overhead::
1761 expansion due to erasure coding
1762 share management data (leases)
1763 backend (ext3) minimum block size
1765 ``POST $URL?t=stream-manifest``
1767 This operation performs a recursive walk of all files and directories
1768 reachable from the given starting point. For each such unique object
1769 (duplicates are skipped), a single line of JSON is emitted to the HTTP
1770 response channel (or an error indication, see below). When the walk is
1771 complete, a final line of JSON is emitted which contains the accumulated
1772 file-size/count "deep-stats" data.
1774 A CLI tool can split the response stream on newlines into "response units",
1775 and parse each response unit as JSON. Each such parsed unit will be a
1776 dictionary, and will contain at least the "type" key: a string, one of
1777 "file", "directory", or "stats".
1779 For all units that have a type of "file" or "directory", the dictionary will
1780 contain the following keys::
1782 "path": a list of strings, with the path that is traversed to reach the
1784 "cap": a write-cap URI for the file or directory, if available, else a
1786 "verifycap": a verify-cap URI for the file or directory
1787 "repaircap": an URI for the weakest cap that can still be used to repair
1789 "storage-index": a base32 storage index for the object
1791 Note that non-distributed files (i.e. LIT files) will have values of None
1792 for verifycap, repaircap, and storage-index, since these files can neither
1793 be verified nor repaired, and are not stored on the storage servers.
1795 The last unit in the stream will have a type of "stats", and will contain
1796 the keys described in the "start-deep-stats" operation, below.
1798 If any errors occur during the traversal (specifically if a directory is
1799 unrecoverable, such that further traversal is not possible), an error
1800 indication is written to the response body, instead of the usual line of
1801 JSON. This error indication line will begin with the string "ERROR:" (in all
1802 caps), and contain a summary of the error on the rest of the line. The
1803 remaining lines of the response body will be a python exception. The client
1804 application should look for the ERROR: and stop processing JSON as soon as
1805 it is seen. The line just before the ERROR: will describe the directory that
1806 was untraversable, since the manifest entry is emitted to the HTTP response
1807 body before the child is traversed.
1813 The portion of the web namespace that begins with "/uri" (and "/named") is
1814 dedicated to giving users (both humans and programs) access to the Tahoe
1815 virtual filesystem. The rest of the namespace provides status information
1816 about the state of the Tahoe node.
1818 ``GET /`` (the root page)
1820 This is the "Welcome Page", and contains a few distinct sections::
1822 Node information: library versions, local nodeid, services being provided.
1824 Filesystem Access Forms: create a new directory, view a file/directory by
1825 URI, upload a file (unlinked), download a file by
1828 Grid Status: introducer information, helper information, connected storage
1833 This page lists all active uploads and downloads, and contains a short list
1834 of recent upload/download operations. Each operation has a link to a page
1835 that describes file sizes, servers that were involved, and the time consumed
1836 in each phase of the operation.
1838 A GET of /status/?t=json will contain a machine-readable subset of the same
1839 data. It returns a JSON-encoded dictionary. The only key defined at this
1840 time is "active", with a value that is a list of operation dictionaries, one
1841 for each active operation. Once an operation is completed, it will no longer
1842 appear in data["active"] .
1844 Each op-dict contains a "type" key, one of "upload", "download",
1845 "mapupdate", "publish", or "retrieve" (the first two are for immutable
1846 files, while the latter three are for mutable files and directories).
1848 The "upload" op-dict will contain the following keys::
1850 type (string): "upload"
1851 storage-index-string (string): a base32-encoded storage index
1852 total-size (int): total size of the file
1853 status (string): current status of the operation
1854 progress-hash (float): 1.0 when the file has been hashed
1855 progress-ciphertext (float): 1.0 when the file has been encrypted.
1856 progress-encode-push (float): 1.0 when the file has been encoded and
1857 pushed to the storage servers. For helper
1858 uploads, the ciphertext value climbs to 1.0
1859 first, then encoding starts. For unassisted
1860 uploads, ciphertext and encode-push progress
1861 will climb at the same pace.
1863 The "download" op-dict will contain the following keys::
1865 type (string): "download"
1866 storage-index-string (string): a base32-encoded storage index
1867 total-size (int): total size of the file
1868 status (string): current status of the operation
1869 progress (float): 1.0 when the file has been fully downloaded
1871 Front-ends which want to report progress information are advised to simply
1872 average together all the progress-* indicators. A slightly more accurate
1873 value can be found by ignoring the progress-hash value (since the current
1874 implementation hashes synchronously, so clients will probably never see
1875 progress-hash!=1.0).
1877 ``GET /helper_status/``
1879 If the node is running a helper (i.e. if [helper]enabled is set to True in
1880 tahoe.cfg), then this page will provide a list of all the helper operations
1881 currently in progress. If "?t=json" is added to the URL, it will return a
1882 JSON-formatted list of helper statistics, which can then be used to produce
1883 graphs to indicate how busy the helper is.
1885 ``GET /statistics/``
1887 This page provides "node statistics", which are collected from a variety of
1890 load_monitor: every second, the node schedules a timer for one second in
1891 the future, then measures how late the subsequent callback
1892 is. The "load_average" is this tardiness, measured in
1893 seconds, averaged over the last minute. It is an indication
1894 of a busy node, one which is doing more work than can be
1895 completed in a timely fashion. The "max_load" value is the
1896 highest value that has been seen in the last 60 seconds.
1898 cpu_monitor: every minute, the node uses time.clock() to measure how much
1899 CPU time it has used, and it uses this value to produce
1900 1min/5min/15min moving averages. These values range from 0%
1901 (0.0) to 100% (1.0), and indicate what fraction of the CPU
1902 has been used by the Tahoe node. Not all operating systems
1903 provide meaningful data to time.clock(): they may report 100%
1904 CPU usage at all times.
1906 uploader: this counts how many immutable files (and bytes) have been
1907 uploaded since the node was started
1909 downloader: this counts how many immutable files have been downloaded
1910 since the node was started
1912 publishes: this counts how many mutable files (including directories) have
1913 been modified since the node was started
1915 retrieves: this counts how many mutable files (including directories) have
1916 been read since the node was started
1918 There are other statistics that are tracked by the node. The "raw stats"
1919 section shows a formatted dump of all of them.
1921 By adding "?t=json" to the URL, the node will return a JSON-formatted
1922 dictionary of stats values, which can be used by other tools to produce
1923 graphs of node behavior. The misc/munin/ directory in the source
1924 distribution provides some tools to produce these graphs.
1926 ``GET /`` (introducer status)
1928 For Introducer nodes, the welcome page displays information about both
1929 clients and servers which are connected to the introducer. Servers make
1930 "service announcements", and these are listed in a table. Clients will
1931 subscribe to hear about service announcements, and these subscriptions are
1932 listed in a separate table. Both tables contain information about what
1933 version of Tahoe is being run by the remote node, their advertised and
1934 outbound IP addresses, their nodeid and nickname, and how long they have
1937 By adding "?t=json" to the URL, the node will return a JSON-formatted
1938 dictionary of stats values, which can be used to produce graphs of connected
1939 clients over time. This dictionary has the following keys::
1941 ["subscription_summary"] : a dictionary mapping service name (like
1942 "storage") to an integer with the number of
1943 clients that have subscribed to hear about that
1945 ["announcement_summary"] : a dictionary mapping service name to an integer
1946 with the number of servers which are announcing
1948 ["announcement_distinct_hosts"] : a dictionary mapping service name to an
1949 integer which represents the number of
1950 distinct hosts that are providing that
1951 service. If two servers have announced
1952 FURLs which use the same hostnames (but
1953 different ports and tubids), they are
1954 considered to be on the same host.
1957 Static Files in /public_html
1958 ============================
1960 The web-API server will take any request for a URL that starts with /static
1961 and serve it from a configurable directory which defaults to
1962 $BASEDIR/public_html . This is configured by setting the "[node]web.static"
1963 value in $BASEDIR/tahoe.cfg . If this is left at the default value of
1964 "public_html", then http://127.0.0.1:3456/static/subdir/foo.html will be
1965 served with the contents of the file $BASEDIR/public_html/subdir/foo.html .
1967 This can be useful to serve a javascript application which provides a
1968 prettier front-end to the rest of the Tahoe web-API.
1971 Safety and Security Issues -- Names vs. URIs
1972 ============================================
1974 Summary: use explicit file- and dir- caps whenever possible, to reduce the
1975 potential for surprises when the filesystem structure is changed.
1977 Tahoe provides a mutable filesystem, but the ways that the filesystem can
1978 change are limited. The only thing that can change is that the mapping from
1979 child names to child objects that each directory contains can be changed by
1980 adding a new child name pointing to an object, removing an existing child name,
1981 or changing an existing child name to point to a different object.
1983 Obviously if you query Tahoe for information about the filesystem and then act
1984 to change the filesystem (such as by getting a listing of the contents of a
1985 directory and then adding a file to the directory), then the filesystem might
1986 have been changed after you queried it and before you acted upon it. However,
1987 if you use the URI instead of the pathname of an object when you act upon the
1988 object, then the only change that can happen is if the object is a directory
1989 then the set of child names it has might be different. If, on the other hand,
1990 you act upon the object using its pathname, then a different object might be in
1991 that place, which can result in more kinds of surprises.
1993 For example, suppose you are writing code which recursively downloads the
1994 contents of a directory. The first thing your code does is fetch the listing
1995 of the contents of the directory. For each child that it fetched, if that
1996 child is a file then it downloads the file, and if that child is a directory
1997 then it recurses into that directory. Now, if the download and the recurse
1998 actions are performed using the child's name, then the results might be
1999 wrong, because for example a child name that pointed to a sub-directory when
2000 you listed the directory might have been changed to point to a file (in which
2001 case your attempt to recurse into it would result in an error and the file
2002 would be skipped), or a child name that pointed to a file when you listed the
2003 directory might now point to a sub-directory (in which case your attempt to
2004 download the child would result in a file containing HTML text describing the
2007 If your recursive algorithm uses the uri of the child instead of the name of
2008 the child, then those kinds of mistakes just can't happen. Note that both the
2009 child's name and the child's URI are included in the results of listing the
2010 parent directory, so it isn't any harder to use the URI for this purpose.
2012 The read and write caps in a given directory node are separate URIs, and
2013 can't be assumed to point to the same object even if they were retrieved in
2014 the same operation (although the web-API server attempts to ensure this
2015 in most cases). If you need to rely on that property, you should explicitly
2016 verify it. More generally, you should not make assumptions about the
2017 internal consistency of the contents of mutable directories. As a result
2018 of the signatures on mutable object versions, it is guaranteed that a given
2019 version was written in a single update, but -- as in the case of a file --
2020 the contents may have been chosen by a malicious writer in a way that is
2021 designed to confuse applications that rely on their consistency.
2023 In general, use names if you want "whatever object (whether file or
2024 directory) is found by following this name (or sequence of names) when my
2025 request reaches the server". Use URIs if you want "this particular object".
2031 Tahoe uses both mutable and immutable files. Mutable files can be created
2032 explicitly by doing an upload with ?mutable=true added, or implicitly by
2033 creating a new directory (since a directory is just a special way to
2034 interpret a given mutable file).
2036 Mutable files suffer from the same consistency-vs-availability tradeoff that
2037 all distributed data storage systems face. It is not possible to
2038 simultaneously achieve perfect consistency and perfect availability in the
2039 face of network partitions (servers being unreachable or faulty).
2041 Tahoe tries to achieve a reasonable compromise, but there is a basic rule in
2042 place, known as the Prime Coordination Directive: "Don't Do That". What this
2043 means is that if write-access to a mutable file is available to several
2044 parties, then those parties are responsible for coordinating their activities
2045 to avoid multiple simultaneous updates. This could be achieved by having
2046 these parties talk to each other and using some sort of locking mechanism, or
2047 by serializing all changes through a single writer.
2049 The consequences of performing uncoordinated writes can vary. Some of the
2050 writers may lose their changes, as somebody else wins the race condition. In
2051 many cases the file will be left in an "unhealthy" state, meaning that there
2052 are not as many redundant shares as we would like (reducing the reliability
2053 of the file against server failures). In the worst case, the file can be left
2054 in such an unhealthy state that no version is recoverable, even the old ones.
2055 It is this small possibility of data loss that prompts us to issue the Prime
2056 Coordination Directive.
2058 Tahoe nodes implement internal serialization to make sure that a single Tahoe
2059 node cannot conflict with itself. For example, it is safe to issue two
2060 directory modification requests to a single tahoe node's web-API server at the
2061 same time, because the Tahoe node will internally delay one of them until
2062 after the other has finished being applied. (This feature was introduced in
2063 Tahoe-1.1; back with Tahoe-1.0 the web client was responsible for serializing
2064 web requests themselves).
2066 For more details, please see the "Consistency vs Availability" and "The Prime
2067 Coordination Directive" sections of `mutable.rst <../specifications/mutable.rst>`_.
2073 Gateway nodes may find it necessary to prohibit access to certain files. The
2074 web-API has a facility to block access to filecaps by their storage index,
2075 returning a 403 "Forbidden" error instead of the original file.
2077 This blacklist is recorded in $NODEDIR/access.blacklist, and contains one
2078 blocked file per line. Comment lines (starting with ``#``) are ignored. Each
2079 line consists of the storage-index (in the usual base32 format as displayed
2080 by the "More Info" page, or by the "tahoe debug dump-cap" command), followed
2081 by whitespace, followed by a reason string, which will be included in the 403
2082 error message. This could hold a URL to a page that explains why the file is
2083 blocked, for example.
2085 So for example, if you found a need to block access to a file with filecap
2086 ``URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861``,
2087 you could do the following::
2089 tahoe debug dump-cap URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2090 -> storage index: whpepioyrnff7orecjolvbudeu
2091 echo "whpepioyrnff7orecjolvbudeu my puppy told me to" >>$NODEDIR/access.blacklist
2092 tahoe restart $NODEDIR
2093 tahoe get URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2094 -> error, 403 Access Prohibited: my puppy told me to
2096 The ``access.blacklist`` file will be checked each time a file or directory
2097 is accessed: the file's ``mtime`` is used to decide whether it need to be
2098 reloaded. Therefore no node restart is necessary when creating the initial
2099 blacklist, nor when adding second, third, or additional entries to the list.
2100 When modifying the file, be careful to update it atomically, otherwise a
2101 request may arrive while the file is only halfway written, and the partial
2102 file may be incorrectly parsed.
2104 The blacklist is applied to all access paths (including SFTP, FTP, and CLI
2105 operations), not just the web-API. The blacklist also applies to directories.
2106 If a directory is blacklisted, the gateway will refuse access to both that
2107 directory and any child files/directories underneath it, when accessed via
2108 "DIRCAP/SUBDIR/FILENAME" -style URLs. Users who go directly to the child
2109 file/dir will bypass the blacklist.
2111 The node will log the SI of the file being blocked, and the reason code, into
2112 the ``logs/twistd.log`` file.
2115 .. [1] URLs and HTTP and UTF-8, Oh My
2117 HTTP does not provide a mechanism to specify the character set used to
2118 encode non-ASCII names in URLs
2119 (`RFC3986#2.1 <https://tools.ietf.org/html/rfc3986#section-2.1>`_).
2120 We prefer the convention that the ``filename=`` argument shall be a
2121 URL-escaped UTF-8 encoded Unicode string.
2122 For example, suppose we want to provoke the server into using a filename of
2123 "f i a n c e-acute e" (i.e. f i a n c U+00E9 e). The UTF-8 encoding of this
2124 is 0x66 0x69 0x61 0x6e 0x63 0xc3 0xa9 0x65 (or "fianc\\xC3\\xA9e", as python's
2125 ``repr()`` function would show). To encode this into a URL, the non-printable
2126 characters must be escaped with the urlencode ``%XX`` mechanism, giving
2127 us "fianc%C3%A9e". Thus, the first line of the HTTP request will be
2128 "``GET /uri/CAP...?save=true&filename=fianc%C3%A9e HTTP/1.1``". Not all
2129 browsers provide this: IE7 by default uses the Latin-1 encoding, which is
2130 "fianc%E9e" (although it has a configuration option to send URLs as UTF-8).
2132 The response header will need to indicate a non-ASCII filename. The actual
2133 mechanism to do this is not clear. For ASCII filenames, the response header
2136 Content-Disposition: attachment; filename="english.txt"
2138 If Tahoe were to enforce the UTF-8 convention, it would need to decode the
2139 URL argument into a Unicode string, and then encode it back into a sequence
2140 of bytes when creating the response header. One possibility would be to use
2141 unencoded UTF-8. Developers suggest that IE7 might accept this::
2143 #1: Content-Disposition: attachment; filename="fianc\xC3\xA9e"
2144 (note, the last four bytes of that line, not including the newline, are
2145 0xC3 0xA9 0x65 0x22)
2147 `RFC2231#4 <https://tools.ietf.org/html/rfc2231#section-4>`_
2148 (dated 1997): suggests that the following might work, and
2149 `some developers have reported <http://markmail.org/message/dsjyokgl7hv64ig3>`_
2150 that it is supported by Firefox (but not IE7)::
2152 #2: Content-Disposition: attachment; filename*=utf-8''fianc%C3%A9e
2154 My reading of `RFC2616#19.5.1 <https://tools.ietf.org/html/rfc2616#section-19.5.1>`_
2155 (which defines Content-Disposition) says that the filename= parameter is
2156 defined to be wrapped in quotes (presumably to allow spaces without breaking
2157 the parsing of subsequent parameters), which would give us::
2159 #3: Content-Disposition: attachment; filename*=utf-8''"fianc%C3%A9e"
2161 However this is contrary to the examples in the email thread listed above.
2163 Developers report that IE7 (when it is configured for UTF-8 URL encoding,
2164 which is not the default in Asian countries), will accept::
2166 #4: Content-Disposition: attachment; filename=fianc%C3%A9e
2168 However, for maximum compatibility, Tahoe simply copies bytes from the URL
2169 into the response header, rather than enforcing the UTF-8 convention. This
2170 means it does not try to decode the filename from the URL argument, nor does
2171 it encode the filename into the response header.