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`_
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:...",
464 "ctime": 1202777696.7564139,
465 "mtime": 1202777696.7564139,
467 "linkcrtime": 1202777696.7564139,
468 "linkmotime": 1202777696.7564139
470 "subdir": [ "dirnode", {
471 "rw_uri": "URI:DIR2:...",
472 "ro_uri": "URI:DIR2-RO:...",
474 "ctime": 1202778102.7589991,
475 "mtime": 1202778111.2160511,
477 "linkcrtime": 1202777696.7564139,
478 "linkmotime": 1202777696.7564139
482 For forward-compatibility, a mutable directory can also contain caps in
483 a format that is unknown to the web-API server. When such caps are retrieved
484 from a mutable directory in a "ro_uri" field, they will be prefixed with
485 the string "ro.", indicating that they must not be decoded without
486 checking that they are read-only. The "ro." prefix must not be stripped
487 off without performing this check. (Future versions of the web-API server
488 will perform it where necessary.)
490 If both the "rw_uri" and "ro_uri" fields are present in a given PROPDICT,
491 and the web-API server recognizes the rw_uri as a write cap, then it will
492 reset the ro_uri to the corresponding read cap and discard the original
493 contents of ro_uri (in order to ensure that the two caps correspond to the
494 same object and that the ro_uri is in fact read-only). However this may not
495 happen for caps in a format unknown to the web-API server. Therefore, when
496 writing a directory the web-API client should ensure that the contents
497 of "rw_uri" and "ro_uri" for a given PROPDICT are a consistent
498 (write cap, read cap) pair if possible. If the web-API client only has
499 one cap and does not know whether it is a write cap or read cap, then
500 it is acceptable to set "rw_uri" to that cap and omit "ro_uri". The
501 client must not put a write cap into a "ro_uri" field.
503 The metadata may have a "no-write" field. If this is set to true in the
504 metadata of a link, it will not be possible to open that link for writing
505 via the SFTP frontend; see `<FTP-and-SFTP.rst>`_ for details.
506 Also, if the "no-write" field is set to true in the metadata of a link to
507 a mutable child, it will cause the link to be diminished to read-only.
509 Note that the web-API-using client application must not provide the
510 "Content-Type: multipart/form-data" header that usually accompanies HTML
511 form submissions, since the body is not formatted this way. Doing so will
512 cause a server error as the lower-level code misparses the request body.
514 Child file names should each be expressed as a Unicode string, then used as
515 keys of the dictionary. The dictionary should then be converted into JSON,
516 and the resulting string encoded into UTF-8. This UTF-8 bytestring should
517 then be used as the POST body.
519 ``POST /uri?t=mkdir-immutable``
521 Like t=mkdir-with-children above, but the new directory will be
522 deep-immutable. This means that the directory itself is immutable, and that
523 it can only contain objects that are treated as being deep-immutable, like
524 immutable files, literal files, and deep-immutable directories.
526 For forward-compatibility, a deep-immutable directory can also contain caps
527 in a format that is unknown to the web-API server. When such caps are retrieved
528 from a deep-immutable directory in a "ro_uri" field, they will be prefixed
529 with the string "imm.", indicating that they must not be decoded without
530 checking that they are immutable. The "imm." prefix must not be stripped
531 off without performing this check. (Future versions of the web-API server
532 will perform it where necessary.)
534 The cap for each child may be given either in the "rw_uri" or "ro_uri"
535 field of the PROPDICT (not both). If a cap is given in the "rw_uri" field,
536 then the web-API server will check that it is an immutable read-cap of a
537 *known* format, and give an error if it is not. If a cap is given in the
538 "ro_uri" field, then the web-API server will still check whether known
539 caps are immutable, but for unknown caps it will simply assume that the
540 cap can be stored, as described above. Note that an attacker would be
541 able to store any cap in an immutable directory, so this check when
542 creating the directory is only to help non-malicious clients to avoid
543 accidentally giving away more authority than intended.
545 A non-empty request body is mandatory, since after the directory is created,
546 it will not be possible to add more children to it.
548 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
550 ``PUT /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
552 Create new directories as necessary to make sure that the named target
553 ($DIRCAP/SUBDIRS../SUBDIR) is a directory. This will create additional
554 intermediate mutable directories as necessary. If the named target directory
555 already exists, this will make no changes to it.
557 If the final directory is created, it will be empty.
559 This accepts a format= argument in the query string, which controls the
560 format of the named target directory, if it does not already exist. format=
561 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
562 format= only controls the format of the named target directory;
563 intermediate directories, if created, are created based on the default
564 mutable type, as configured on the Tahoe-LAFS server responding to the
567 This operation will return an error if a blocking file is present at any of
568 the parent names, preventing the server from creating the necessary parent
569 directory; or if it would require changing an immutable directory.
571 The write-cap of the new directory will be returned as the HTTP response
574 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-with-children``
576 Like /uri?t=mkdir-with-children, but the final directory is created as a
577 child of an existing mutable directory. This will create additional
578 intermediate mutable directories as necessary. If the final directory is
579 created, it will be populated with initial children from the POST request
580 body, as described above.
582 This accepts a format= argument in the query string, which controls the
583 format of the target directory, if the target directory is created as part
584 of the operation. format= is interpreted in the same way as in the POST/
585 uri?t=mkdir-with-children operation. Note that format= only controls the
586 format of the named target directory; intermediate directories, if created,
587 are created using the default mutable type setting, as configured on the
588 Tahoe-LAFS server responding to the request.
590 This operation will return an error if a blocking file is present at any of
591 the parent names, preventing the server from creating the necessary parent
592 directory; or if it would require changing an immutable directory; or if
593 the immediate parent directory already has a a child named SUBDIR.
595 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-immutable``
597 Like /uri?t=mkdir-immutable, but the final directory is created as a child
598 of an existing mutable directory. The final directory will be deep-immutable,
599 and will be populated with the children specified as a JSON dictionary in
600 the POST request body.
602 In Tahoe 1.6 this operation creates intermediate mutable directories if
603 necessary, but that behaviour should not be relied on; see ticket #920.
605 This operation will return an error if the parent directory is immutable,
606 or already has a child named SUBDIR.
608 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME``
610 Create a new empty mutable directory and attach it to the given existing
611 directory. This will create additional intermediate directories as necessary.
613 This accepts a format= argument in the query string, which controls the
614 format of the named target directory, if it does not already exist. format=
615 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
616 format= only controls the format of the named target directory;
617 intermediate directories, if created, are created based on the default
618 mutable type, as configured on the Tahoe-LAFS server responding to the
621 This operation will return an error if a blocking file is present at any of
622 the parent names, preventing the server from creating the necessary parent
623 directory, or if it would require changing any immutable directory.
625 The URL of this operation points to the parent of the bottommost new directory,
626 whereas the /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir operation above has a URL
627 that points directly to the bottommost new directory.
629 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME``
631 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME, but the new directory will
632 be populated with initial children via the POST request body. This command
633 will create additional intermediate mutable directories as necessary.
635 This accepts a format= argument in the query string, which controls the
636 format of the target directory, if the target directory is created as part
637 of the operation. format= is interpreted in the same way as in the POST/
638 uri?t=mkdir-with-children operation. Note that format= only controls the
639 format of the named target directory; intermediate directories, if created,
640 are created using the default mutable type setting, as configured on the
641 Tahoe-LAFS server responding to the request.
643 This operation will return an error if a blocking file is present at any of
644 the parent names, preventing the server from creating the necessary parent
645 directory; or if it would require changing an immutable directory; or if
646 the immediate parent directory already has a a child named NAME.
648 Note that the name= argument must be passed as a queryarg, because the POST
649 request body is used for the initial children JSON.
651 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-immutable&name=NAME``
653 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME, but the
654 final directory will be deep-immutable. The children are specified as a
655 JSON dictionary in the POST request body. Again, the name= argument must be
656 passed as a queryarg.
658 In Tahoe 1.6 this operation creates intermediate mutable directories if
659 necessary, but that behaviour should not be relied on; see ticket #920.
661 This operation will return an error if the parent directory is immutable,
662 or already has a child named NAME.
665 Getting Information About A File Or Directory (as JSON)
666 -------------------------------------------------------
668 ``GET /uri/$FILECAP?t=json``
670 ``GET /uri/$DIRCAP?t=json``
672 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json``
674 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json``
676 This returns a machine-parseable JSON-encoded description of the given
677 object. The JSON always contains a list, and the first element of the list is
678 always a flag that indicates whether the referenced object is a file or a
679 directory. If it is a capability to a file, then the information includes
680 file size and URI, like this::
682 GET /uri/$FILECAP?t=json :
686 "verify_uri": verify_uri,
692 If it is a capability to a directory followed by a path from that directory
693 to a file, then the information also includes metadata from the link to the
694 file in the parent directory, like this::
696 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json
700 "verify_uri": verify_uri,
705 "ctime": 1202777696.7564139,
706 "mtime": 1202777696.7564139,
708 "linkcrtime": 1202777696.7564139,
709 "linkmotime": 1202777696.7564139
712 If it is a directory, then it includes information about the children of
713 this directory, as a mapping from child name to a set of data about the
714 child (the same data that would appear in a corresponding GET?t=json of the
715 child itself). The child entries also include metadata about each child,
716 including link-creation- and link-change- timestamps. The output looks like
719 GET /uri/$DIRCAP?t=json :
720 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json :
723 "rw_uri": read_write_uri,
724 "ro_uri": read_only_uri,
725 "verify_uri": verify_uri,
729 "foo.txt": [ "filenode",
734 "ctime": 1202777696.7564139,
735 "mtime": 1202777696.7564139,
737 "linkcrtime": 1202777696.7564139,
738 "linkmotime": 1202777696.7564139
740 "subdir": [ "dirnode",
745 "ctime": 1202778102.7589991,
746 "mtime": 1202778111.2160511,
748 "linkcrtime": 1202777696.7564139,
749 "linkmotime": 1202777696.7564139
753 In the above example, note how 'children' is a dictionary in which the keys
754 are child names and the values depend upon whether the child is a file or a
755 directory. The value is mostly the same as the JSON representation of the
756 child object (except that directories do not recurse -- the "children"
757 entry of the child is omitted, and the directory view includes the metadata
758 that is stored on the directory edge).
760 The rw_uri field will be present in the information about a directory
761 if and only if you have read-write access to that directory. The verify_uri
762 field will be present if and only if the object has a verify-cap
763 (non-distributed LIT files do not have verify-caps).
765 If the cap is of an unknown format, then the file size and verify_uri will
768 GET /uri/$UNKNOWNCAP?t=json :
771 "ro_uri": unknown_read_uri
774 GET /uri/$DIRCAP/[SUBDIRS../]UNKNOWNCHILDNAME?t=json :
777 "rw_uri": unknown_write_uri,
778 "ro_uri": unknown_read_uri,
781 "ctime": 1202777696.7564139,
782 "mtime": 1202777696.7564139,
784 "linkcrtime": 1202777696.7564139,
785 "linkmotime": 1202777696.7564139
788 As in the case of file nodes, the metadata will only be present when the
789 capability is to a directory followed by a path. The "mutable" field is also
790 not always present; when it is absent, the mutability of the object is not
796 The value of the 'tahoe':'linkmotime' key is updated whenever a link to a
797 child is set. The value of the 'tahoe':'linkcrtime' key is updated whenever
798 a link to a child is created -- i.e. when there was not previously a link
801 Note however, that if the edge in the Tahoe filesystem points to a mutable
802 file and the contents of that mutable file is changed, then the
803 'tahoe':'linkmotime' value on that edge will *not* be updated, since the
804 edge itself wasn't updated -- only the mutable file was.
806 The timestamps are represented as a number of seconds since the UNIX epoch
807 (1970-01-01 00:00:00 UTC), with leap seconds not being counted in the long
810 In Tahoe earlier than v1.4.0, 'mtime' and 'ctime' keys were populated
811 instead of the 'tahoe':'linkmotime' and 'tahoe':'linkcrtime' keys. Starting
812 in Tahoe v1.4.0, the 'linkmotime'/'linkcrtime' keys in the 'tahoe' sub-dict
813 are populated. However, prior to Tahoe v1.7beta, a bug caused the 'tahoe'
814 sub-dict to be deleted by web-API requests in which new metadata is
815 specified, and not to be added to existing child links that lack it.
817 From Tahoe v1.7.0 onward, the 'mtime' and 'ctime' fields are no longer
818 populated or updated (see ticket #924), except by "tahoe backup" as
819 explained below. For backward compatibility, when an existing link is
820 updated and 'tahoe':'linkcrtime' is not present in the previous metadata
821 but 'ctime' is, the old value of 'ctime' is used as the new value of
822 'tahoe':'linkcrtime'.
824 The reason we added the new fields in Tahoe v1.4.0 is that there is a
825 "set_children" API (described below) which you can use to overwrite the
826 values of the 'mtime'/'ctime' pair, and this API is used by the
827 "tahoe backup" command (in Tahoe v1.3.0 and later) to set the 'mtime' and
828 'ctime' values when backing up files from a local filesystem into the
829 Tahoe filesystem. As of Tahoe v1.4.0, the set_children API cannot be used
830 to set anything under the 'tahoe' key of the metadata dict -- if you
831 include 'tahoe' keys in your 'metadata' arguments then it will silently
834 Therefore, if the 'tahoe' sub-dict is present, you can rely on the
835 'linkcrtime' and 'linkmotime' values therein to have the semantics described
836 above. (This is assuming that only official Tahoe clients have been used to
837 write those links, and that their system clocks were set to what you expected
838 -- there is nothing preventing someone from editing their Tahoe client or
839 writing their own Tahoe client which would overwrite those values however
840 they like, and there is nothing to constrain their system clock from taking
843 When an edge is created or updated by "tahoe backup", the 'mtime' and
844 'ctime' keys on that edge are set as follows:
846 * 'mtime' is set to the timestamp read from the local filesystem for the
847 "mtime" of the local file in question, which means the last time the
848 contents of that file were changed.
850 * On Windows, 'ctime' is set to the creation timestamp for the file
851 read from the local filesystem. On other platforms, 'ctime' is set to
852 the UNIX "ctime" of the local file, which means the last time that
853 either the contents or the metadata of the local file was changed.
855 There are several ways that the 'ctime' field could be confusing:
857 1. You might be confused about whether it reflects the time of the creation
858 of a link in the Tahoe filesystem (by a version of Tahoe < v1.7.0) or a
859 timestamp copied in by "tahoe backup" from a local filesystem.
861 2. You might be confused about whether it is a copy of the file creation
862 time (if "tahoe backup" was run on a Windows system) or of the last
863 contents-or-metadata change (if "tahoe backup" was run on a different
866 3. You might be confused by the fact that changing the contents of a
867 mutable file in Tahoe doesn't have any effect on any links pointing at
868 that file in any directories, although "tahoe backup" sets the link
869 'ctime'/'mtime' to reflect timestamps about the local file corresponding
870 to the Tahoe file to which the link points.
872 4. Also, quite apart from Tahoe, you might be confused about the meaning
873 of the "ctime" in UNIX local filesystems, which people sometimes think
874 means file creation time, but which actually means, in UNIX local
875 filesystems, the most recent time that the file contents or the file
876 metadata (such as owner, permission bits, extended attributes, etc.)
877 has changed. Note that although "ctime" does not mean file creation time
878 in UNIX, links created by a version of Tahoe prior to v1.7.0, and never
879 written by "tahoe backup", will have 'ctime' set to the link creation
883 Attaching an Existing File or Directory by its read- or write-cap
884 -----------------------------------------------------------------
886 ``PUT /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
888 This attaches a child object (either a file or directory) to a specified
889 location in the virtual filesystem. The child object is referenced by its
890 read- or write- cap, as provided in the HTTP request body. This will create
891 intermediate directories as necessary.
893 This is similar to a UNIX hardlink: by referencing a previously-uploaded file
894 (or previously-created directory) instead of uploading/creating a new one,
895 you can create two references to the same object.
897 The read- or write- cap of the child is provided in the body of the HTTP
898 request, and this same cap is returned in the response body.
900 The default behavior is to overwrite any existing object at the same
901 location. To prevent this (and make the operation return an error instead
902 of overwriting), add a "replace=false" argument, as "?t=uri&replace=false".
903 With replace=false, this operation will return an HTTP 409 "Conflict" error
904 if there is already an object at the given location, rather than
905 overwriting the existing object. To allow the operation to overwrite a
906 file, but return an error when trying to overwrite a directory, use
907 "replace=only-files" (this behavior is closer to the traditional UNIX "mv"
908 command). Note that "true", "t", and "1" are all synonyms for "True", and
909 "false", "f", and "0" are synonyms for "False", and the parameter is
912 Note that this operation does not take its child cap in the form of
913 separate "rw_uri" and "ro_uri" fields. Therefore, it cannot accept a
914 child cap in a format unknown to the web-API server, unless its URI
915 starts with "ro." or "imm.". This restriction is necessary because the
916 server is not able to attenuate an unknown write cap to a read cap.
917 Unknown URIs starting with "ro." or "imm.", on the other hand, are
918 assumed to represent read caps. The client should not prefix a write
919 cap with "ro." or "imm." and pass it to this operation, since that
920 would result in granting the cap's write authority to holders of the
924 Adding Multiple Files or Directories to a Parent Directory at Once
925 ------------------------------------------------------------------
927 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set_children``
929 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set-children`` (Tahoe >= v1.6)
931 This command adds multiple children to a directory in a single operation.
932 It reads the request body and interprets it as a JSON-encoded description
933 of the child names and read/write-caps that should be added.
935 The body should be a JSON-encoded dictionary, in the same format as the
936 "children" value returned by the "GET /uri/$DIRCAP?t=json" operation
937 described above. In this format, each key is a child names, and the
938 corresponding value is a tuple of (type, childinfo). "type" is ignored, and
939 "childinfo" is a dictionary that contains "rw_uri", "ro_uri", and
940 "metadata" keys. You can take the output of "GET /uri/$DIRCAP1?t=json" and
941 use it as the input to "POST /uri/$DIRCAP2?t=set_children" to make DIR2
942 look very much like DIR1 (except for any existing children of DIR2 that
943 were not overwritten, and any existing "tahoe" metadata keys as described
946 When the set_children request contains a child name that already exists in
947 the target directory, this command defaults to overwriting that child with
948 the new value (both child cap and metadata, but if the JSON data does not
949 contain a "metadata" key, the old child's metadata is preserved). The
950 command takes a boolean "overwrite=" query argument to control this
951 behavior. If you use "?t=set_children&overwrite=false", then an attempt to
952 replace an existing child will instead cause an error.
954 Any "tahoe" key in the new child's "metadata" value is ignored. Any
955 existing "tahoe" metadata is preserved. The metadata["tahoe"] value is
956 reserved for metadata generated by the tahoe node itself. The only two keys
957 currently placed here are "linkcrtime" and "linkmotime". For details, see
958 the section above entitled "Get Information About A File Or Directory (as
959 JSON)", in the "About the metadata" subsection.
961 Note that this command was introduced with the name "set_children", which
962 uses an underscore rather than a hyphen as other multi-word command names
963 do. The variant with a hyphen is now accepted, but clients that desire
964 backward compatibility should continue to use "set_children".
967 Unlinking a File or Directory
968 -----------------------------
970 ``DELETE /uri/$DIRCAP/[SUBDIRS../]CHILDNAME``
972 This removes the given name from its parent directory. CHILDNAME is the
973 name to be removed, and $DIRCAP/SUBDIRS.. indicates the directory that will
976 Note that this does not actually delete the file or directory that the name
977 points to from the tahoe grid -- it only unlinks the named reference from
978 this directory. If there are other names in this directory or in other
979 directories that point to the resource, then it will remain accessible
980 through those paths. Even if all names pointing to this object are removed
981 from their parent directories, then someone with possession of its read-cap
982 can continue to access the object through that cap.
984 The object will only become completely unreachable once 1: there are no
985 reachable directories that reference it, and 2: nobody is holding a read-
986 or write- cap to the object. (This behavior is very similar to the way
987 hardlinks and anonymous files work in traditional UNIX filesystems).
989 This operation will not modify more than a single directory. Intermediate
990 directories which were implicitly created by PUT or POST methods will *not*
991 be automatically removed by DELETE.
993 This method returns the file- or directory- cap of the object that was just
997 Browser Operations: Human-oriented interfaces
998 =============================================
1000 This section describes the HTTP operations that provide support for humans
1001 running a web browser. Most of these operations use HTML forms that use POST
1002 to drive the Tahoe node. This section is intended for HTML authors who want
1003 to write web pages that contain forms and buttons which manipulate the Tahoe
1006 Note that for all POST operations, the arguments listed can be provided
1007 either as URL query arguments or as form body fields. URL query arguments are
1008 separated from the main URL by "?", and from each other by "&". For example,
1009 "POST /uri/$DIRCAP?t=upload&mutable=true". Form body fields are usually
1010 specified by using <input type="hidden"> elements. For clarity, the
1011 descriptions below display the most significant arguments as URL query args.
1014 Viewing A Directory (as HTML)
1015 -----------------------------
1017 ``GET /uri/$DIRCAP/[SUBDIRS../]``
1019 This returns an HTML page, intended to be displayed to a human by a web
1020 browser, which contains HREF links to all files and directories reachable
1021 from this directory. These HREF links do not have a t= argument, meaning
1022 that a human who follows them will get pages also meant for a human. It also
1023 contains forms to upload new files, and to unlink files and directories
1024 from their parent directory. Those forms use POST methods to do their job.
1027 Viewing/Downloading a File
1028 --------------------------
1030 ``GET /uri/$FILECAP``
1032 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME``
1034 This will retrieve the contents of the given file. The HTTP response body
1035 will contain the sequence of bytes that make up the file.
1037 If you want the HTTP response to include a useful Content-Type header,
1038 either use the second form (which starts with a $DIRCAP), or add a
1039 "filename=foo" query argument, like "GET /uri/$FILECAP?filename=foo.jpg".
1040 The bare "GET /uri/$FILECAP" does not give the Tahoe node enough information
1041 to determine a Content-Type (since Tahoe immutable files are merely
1042 sequences of bytes, not typed+named file objects).
1044 If the URL has both filename= and "save=true" in the query arguments, then
1045 the server to add a "Content-Disposition: attachment" header, along with a
1046 filename= parameter. When a user clicks on such a link, most browsers will
1047 offer to let the user save the file instead of displaying it inline (indeed,
1048 most browsers will refuse to display it inline). "true", "t", "1", and other
1049 case-insensitive equivalents are all treated the same.
1051 Character-set handling in URLs and HTTP headers is a dubious art [1]_. For
1052 maximum compatibility, Tahoe simply copies the bytes from the filename=
1053 argument into the Content-Disposition header's filename= parameter, without
1054 trying to interpret them in any particular way.
1057 ``GET /named/$FILECAP/FILENAME``
1059 This is an alternate download form which makes it easier to get the correct
1060 filename. The Tahoe server will provide the contents of the given file, with
1061 a Content-Type header derived from the given filename. This form is used to
1062 get browsers to use the "Save Link As" feature correctly, and also helps
1063 command-line tools like "wget" and "curl" use the right filename. Note that
1064 this form can *only* be used with file caps; it is an error to use a
1065 directory cap after the /named/ prefix.
1067 URLs may also use /file/$FILECAP/FILENAME as a synonym for
1068 /named/$FILECAP/FILENAME.
1070 Getting Information About A File Or Directory (as HTML)
1071 -------------------------------------------------------
1073 ``GET /uri/$FILECAP?t=info``
1075 ``GET /uri/$DIRCAP/?t=info``
1077 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR/?t=info``
1079 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=info``
1081 This returns a human-oriented HTML page with more detail about the selected
1082 file or directory object. This page contains the following items:
1086 * JSON representation
1087 * raw contents (text/plain)
1088 * access caps (URIs): verify-cap, read-cap, write-cap (for mutable objects)
1089 * check/verify/repair form
1090 * deep-check/deep-size/deep-stats/manifest (for directories)
1091 * replace-contents form (for mutable files)
1094 Creating a Directory
1095 --------------------
1097 ``POST /uri?t=mkdir``
1099 This creates a new empty directory, but does not attach it to the virtual
1102 If a "redirect_to_result=true" argument is provided, then the HTTP response
1103 will cause the web browser to be redirected to a /uri/$DIRCAP page that
1104 gives access to the newly-created directory. If you bookmark this page,
1105 you'll be able to get back to the directory again in the future. This is the
1106 recommended way to start working with a Tahoe server: create a new unlinked
1107 directory (using redirect_to_result=true), then bookmark the resulting
1108 /uri/$DIRCAP page. There is a "create directory" button on the Welcome page
1109 to invoke this action.
1111 This accepts a format= argument in the query string. Refer to the
1112 documentation of the PUT /uri?t=mkdir operation in `Creating A
1113 New Directory`_ for information on the behavior of the format= argument.
1115 If "redirect_to_result=true" is not provided (or is given a value of
1116 "false"), then the HTTP response body will simply be the write-cap of the
1119 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME``
1121 This creates a new empty directory as a child of the designated SUBDIR. This
1122 will create additional intermediate directories as necessary.
1124 This accepts a format= argument in the query string. Refer to the
1125 documentation of POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME in
1126 `Creating A New Directory`_ for information on the behavior of the format=
1129 If a "when_done=URL" argument is provided, the HTTP response will cause the
1130 web browser to redirect to the given URL. This provides a convenient way to
1131 return the browser to the directory that was just modified. Without a
1132 when_done= argument, the HTTP response will simply contain the write-cap of
1133 the directory that was just created.
1139 ``POST /uri?t=upload``
1141 This uploads a file, and produces a file-cap for the contents, but does not
1142 attach the file into the filesystem. No directories will be modified by
1145 The file must be provided as the "file" field of an HTML encoded form body,
1146 produced in response to an HTML form like this::
1148 <form action="/uri" method="POST" enctype="multipart/form-data">
1149 <input type="hidden" name="t" value="upload" />
1150 <input type="file" name="file" />
1151 <input type="submit" value="Upload Unlinked" />
1154 If a "when_done=URL" argument is provided, the response body will cause the
1155 browser to redirect to the given URL. If the when_done= URL has the string
1156 "%(uri)s" in it, that string will be replaced by a URL-escaped form of the
1157 newly created file-cap. (Note that without this substitution, there is no
1158 way to access the file that was just uploaded).
1160 The default (in the absence of when_done=) is to return an HTML page that
1161 describes the results of the upload. This page will contain information
1162 about which storage servers were used for the upload, how long each
1163 operation took, etc.
1165 This accepts format= and mutable=true query string arguments. Refer to
1166 `Writing/Uploading A File`_ for information on the behavior of format= and
1169 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=upload``
1171 This uploads a file, and attaches it as a new child of the given directory,
1172 which must be mutable. The file must be provided as the "file" field of an
1173 HTML-encoded form body, produced in response to an HTML form like this::
1175 <form action="." method="POST" enctype="multipart/form-data">
1176 <input type="hidden" name="t" value="upload" />
1177 <input type="file" name="file" />
1178 <input type="submit" value="Upload" />
1181 A "name=" argument can be provided to specify the new child's name,
1182 otherwise it will be taken from the "filename" field of the upload form
1183 (most web browsers will copy the last component of the original file's
1184 pathname into this field). To avoid confusion, name= is not allowed to
1187 If there is already a child with that name, and it is a mutable file, then
1188 its contents are replaced with the data being uploaded. If it is not a
1189 mutable file, the default behavior is to remove the existing child before
1190 creating a new one. To prevent this (and make the operation return an error
1191 instead of overwriting the old child), add a "replace=false" argument, as
1192 "?t=upload&replace=false". With replace=false, this operation will return an
1193 HTTP 409 "Conflict" error if there is already an object at the given
1194 location, rather than overwriting the existing object. Note that "true",
1195 "t", and "1" are all synonyms for "True", and "false", "f", and "0" are
1196 synonyms for "False". the parameter is case-insensitive.
1198 This will create additional intermediate directories as necessary, although
1199 since it is expected to be triggered by a form that was retrieved by "GET
1200 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1203 This accepts format= and mutable=true query string arguments. Refer to
1204 `Writing/Uploading A File`_ for information on the behavior of format= and
1207 If a "when_done=URL" argument is provided, the HTTP response will cause the
1208 web browser to redirect to the given URL. This provides a convenient way to
1209 return the browser to the directory that was just modified. Without a
1210 when_done= argument, the HTTP response will simply contain the file-cap of
1211 the file that was just uploaded (a write-cap for mutable files, or a
1212 read-cap for immutable files).
1214 ``POST /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=upload``
1216 This also uploads a file and attaches it as a new child of the given
1217 directory, which must be mutable. It is a slight variant of the previous
1218 operation, as the URL refers to the target file rather than the parent
1219 directory. It is otherwise identical: this accepts mutable= and when_done=
1222 ``POST /uri/$FILECAP?t=upload``
1224 This modifies the contents of an existing mutable file in-place. An error is
1225 signalled if $FILECAP does not refer to a mutable file. It behaves just like
1226 the "PUT /uri/$FILECAP" form, but uses a POST for the benefit of HTML forms
1230 Attaching An Existing File Or Directory (by URI)
1231 ------------------------------------------------
1233 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=uri&name=CHILDNAME&uri=CHILDCAP``
1235 This attaches a given read- or write- cap "CHILDCAP" to the designated
1236 directory, with a specified child name. This behaves much like the PUT t=uri
1237 operation, and is a lot like a UNIX hardlink. It is subject to the same
1238 restrictions as that operation on the use of cap formats unknown to the
1241 This will create additional intermediate directories as necessary, although
1242 since it is expected to be triggered by a form that was retrieved by "GET
1243 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1246 This accepts the same replace= argument as POST t=upload.
1252 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=delete&name=CHILDNAME``
1254 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=unlink&name=CHILDNAME``
1256 This instructs the node to remove a child object (file or subdirectory) from
1257 the given directory, which must be mutable. Note that the entire subtree is
1258 unlinked from the parent. Unlike deleting a subdirectory in a UNIX local
1259 filesystem, the subtree need not be empty; if it isn't, then other references
1260 into the subtree will see that the child subdirectories are not modified by
1261 this operation. Only the link from the given directory to its child is severed.
1263 In Tahoe-LAFS v1.9.0 and later, t=unlink can be used as a synonym for t=delete.
1264 If interoperability with older web-API servers is required, t=delete should
1271 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=rename&from_name=OLD&to_name=NEW``
1273 This instructs the node to rename a child of the given directory, which must
1274 be mutable. This has a similar effect to removing the child, then adding the
1275 same child-cap under the new name, except that it preserves metadata. This
1276 operation cannot move the child to a different directory.
1278 This operation will replace any existing child of the new name, making it
1279 behave like the UNIX "``mv -f``" command.
1284 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=rename&from_name=OLD&to_dir=TARGET[&to_name=NEW]``
1286 This instructs the node to move a child of the given directory to a
1287 different directory, both of which must be mutable. The child can also be
1288 renamed in the process. The to_dir parameter can be either the name of a
1289 subdirectory of the dircap from which the child is being moved (multiple
1290 levels of descent are supported) or the writecap of an unrelated directory.
1292 This operation will replace any existing child of the new name, making it
1293 behave like the UNIX "``mv -f``" command. The original child is not
1294 unlinked until it is linked into the target directory.
1299 ``GET /uri?uri=$CAP``
1301 This causes a redirect to /uri/$CAP, and retains any additional query
1302 arguments (like filename= or save=). This is for the convenience of web
1303 forms which allow the user to paste in a read- or write- cap (obtained
1304 through some out-of-band channel, like IM or email).
1306 Note that this form merely redirects to the specific file or directory
1307 indicated by the $CAP: unlike the GET /uri/$DIRCAP form, you cannot
1308 traverse to children by appending additional path segments to the URL.
1310 ``GET /uri/$DIRCAP/[SUBDIRS../]?t=rename-form&name=$CHILDNAME``
1312 This provides a useful facility to browser-based user interfaces. It
1313 returns a page containing a form targetting the "POST $DIRCAP t=rename"
1314 functionality described above, with the provided $CHILDNAME present in the
1315 'from_name' field of that form. I.e. this presents a form offering to
1316 rename $CHILDNAME, requesting the new name, and submitting POST rename.
1317 This same URL format can also be used with "move-form" with the expected
1320 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
1322 This returns the file- or directory- cap for the specified object.
1324 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=readonly-uri``
1326 This returns a read-only file- or directory- cap for the specified object.
1327 If the object is an immutable file, this will return the same value as
1331 Debugging and Testing Features
1332 ------------------------------
1334 These URLs are less-likely to be helpful to the casual Tahoe user, and are
1335 mainly intended for developers.
1337 ``POST $URL?t=check``
1339 This triggers the FileChecker to determine the current "health" of the
1340 given file or directory, by counting how many shares are available. The
1341 page that is returned will display the results. This can be used as a "show
1342 me detailed information about this file" page.
1344 If a verify=true argument is provided, the node will perform a more
1345 intensive check, downloading and verifying every single bit of every share.
1347 If an add-lease=true argument is provided, the node will also add (or
1348 renew) a lease to every share it encounters. Each lease will keep the share
1349 alive for a certain period of time (one month by default). Once the last
1350 lease expires or is explicitly cancelled, the storage server is allowed to
1353 If an output=JSON argument is provided, the response will be
1354 machine-readable JSON instead of human-oriented HTML. The data is a
1355 dictionary with the following keys::
1357 storage-index: a base32-encoded string with the objects's storage index,
1358 or an empty string for LIT files
1359 summary: a string, with a one-line summary of the stats of the file
1360 results: a dictionary that describes the state of the file. For LIT files,
1361 this dictionary has only the 'healthy' key, which will always be
1362 True. For distributed files, this dictionary has the following
1364 count-shares-good: the number of good shares that were found
1365 count-shares-needed: 'k', the number of shares required for recovery
1366 count-shares-expected: 'N', the number of total shares generated
1367 count-good-share-hosts: this was intended to be the number of distinct
1368 storage servers with good shares. It is currently
1369 (as of Tahoe-LAFS v1.8.0) computed incorrectly;
1371 count-wrong-shares: for mutable files, the number of shares for
1372 versions other than the 'best' one (highest
1373 sequence number, highest roothash). These are
1375 count-recoverable-versions: for mutable files, the number of
1376 recoverable versions of the file. For
1377 a healthy file, this will equal 1.
1378 count-unrecoverable-versions: for mutable files, the number of
1379 unrecoverable versions of the file.
1380 For a healthy file, this will be 0.
1381 count-corrupt-shares: the number of shares with integrity failures
1382 list-corrupt-shares: a list of "share locators", one for each share
1383 that was found to be corrupt. Each share locator
1384 is a list of (serverid, storage_index, sharenum).
1385 needs-rebalancing: (bool) True if there are multiple shares on a single
1386 storage server, indicating a reduction in reliability
1387 that could be resolved by moving shares to new
1389 servers-responding: list of base32-encoded storage server identifiers,
1390 one for each server which responded to the share
1392 healthy: (bool) True if the file is completely healthy, False otherwise.
1393 Healthy files have at least N good shares. Overlapping shares
1394 do not currently cause a file to be marked unhealthy. If there
1395 are at least N good shares, then corrupt shares do not cause the
1396 file to be marked unhealthy, although the corrupt shares will be
1397 listed in the results (list-corrupt-shares) and should be manually
1398 removed to wasting time in subsequent downloads (as the
1399 downloader rediscovers the corruption and uses alternate shares).
1400 Future compatibility: the meaning of this field may change to
1401 reflect whether the servers-of-happiness criterion is met
1403 sharemap: dict mapping share identifier to list of serverids
1404 (base32-encoded strings). This indicates which servers are
1405 holding which shares. For immutable files, the shareid is
1406 an integer (the share number, from 0 to N-1). For
1407 immutable files, it is a string of the form
1408 'seq%d-%s-sh%d', containing the sequence number, the
1409 roothash, and the share number.
1411 ``POST $URL?t=start-deep-check`` (must add &ophandle=XYZ)
1413 This initiates a recursive walk of all files and directories reachable from
1414 the target, performing a check on each one just like t=check. The result
1415 page will contain a summary of the results, including details on any
1416 file/directory that was not fully healthy.
1418 t=start-deep-check can only be invoked on a directory. An error (400
1419 BAD_REQUEST) will be signalled if it is invoked on a file. The recursive
1420 walker will deal with loops safely.
1422 This accepts the same verify= and add-lease= arguments as t=check.
1424 Since this operation can take a long time (perhaps a second per object),
1425 the ophandle= argument is required (see "Slow Operations, Progress, and
1426 Cancelling" above). The response to this POST will be a redirect to the
1427 corresponding /operations/$HANDLE page (with output=HTML or output=JSON to
1428 match the output= argument given to the POST). The deep-check operation
1429 will continue to run in the background, and the /operations page should be
1430 used to find out when the operation is done.
1432 Detailed check results for non-healthy files and directories will be
1433 available under /operations/$HANDLE/$STORAGEINDEX, and the HTML status will
1434 contain links to these detailed results.
1436 The HTML /operations/$HANDLE page for incomplete operations will contain a
1437 meta-refresh tag, set to 60 seconds, so that a browser which uses
1438 deep-check will automatically poll until the operation has completed.
1440 The JSON page (/options/$HANDLE?output=JSON) will contain a
1441 machine-readable JSON dictionary with the following keys::
1443 finished: a boolean, True if the operation is complete, else False. Some
1444 of the remaining keys may not be present until the operation
1446 root-storage-index: a base32-encoded string with the storage index of the
1447 starting point of the deep-check operation
1448 count-objects-checked: count of how many objects were checked. Note that
1449 non-distributed objects (i.e. small immutable LIT
1450 files) are not checked, since for these objects,
1451 the data is contained entirely in the URI.
1452 count-objects-healthy: how many of those objects were completely healthy
1453 count-objects-unhealthy: how many were damaged in some way
1454 count-corrupt-shares: how many shares were found to have corruption,
1455 summed over all objects examined
1456 list-corrupt-shares: a list of "share identifiers", one for each share
1457 that was found to be corrupt. Each share identifier
1458 is a list of (serverid, storage_index, sharenum).
1459 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1460 each file that was not fully healthy. 'pathname' is
1461 a list of strings (which can be joined by "/"
1462 characters to turn it into a single string),
1463 relative to the directory on which deep-check was
1464 invoked. The 'check-results' field is the same as
1465 that returned by t=check&output=JSON, described
1467 stats: a dictionary with the same keys as the t=start-deep-stats command
1470 ``POST $URL?t=stream-deep-check``
1472 This initiates a recursive walk of all files and directories reachable from
1473 the target, performing a check on each one just like t=check. For each
1474 unique object (duplicates are skipped), a single line of JSON is emitted to
1475 the HTTP response channel (or an error indication, see below). When the walk
1476 is complete, a final line of JSON is emitted which contains the accumulated
1477 file-size/count "deep-stats" data.
1479 This command takes the same arguments as t=start-deep-check.
1481 A CLI tool can split the response stream on newlines into "response units",
1482 and parse each response unit as JSON. Each such parsed unit will be a
1483 dictionary, and will contain at least the "type" key: a string, one of
1484 "file", "directory", or "stats".
1486 For all units that have a type of "file" or "directory", the dictionary will
1487 contain the following keys::
1489 "path": a list of strings, with the path that is traversed to reach the
1491 "cap": a write-cap URI for the file or directory, if available, else a
1493 "verifycap": a verify-cap URI for the file or directory
1494 "repaircap": an URI for the weakest cap that can still be used to repair
1496 "storage-index": a base32 storage index for the object
1497 "check-results": a copy of the dictionary which would be returned by
1498 t=check&output=json, with three top-level keys:
1499 "storage-index", "summary", and "results", and a variety
1500 of counts and sharemaps in the "results" value.
1502 Note that non-distributed files (i.e. LIT files) will have values of None
1503 for verifycap, repaircap, and storage-index, since these files can neither
1504 be verified nor repaired, and are not stored on the storage servers.
1505 Likewise the check-results dictionary will be limited: an empty string for
1506 storage-index, and a results dictionary with only the "healthy" key.
1508 The last unit in the stream will have a type of "stats", and will contain
1509 the keys described in the "start-deep-stats" operation, below.
1511 If any errors occur during the traversal (specifically if a directory is
1512 unrecoverable, such that further traversal is not possible), an error
1513 indication is written to the response body, instead of the usual line of
1514 JSON. This error indication line will begin with the string "ERROR:" (in all
1515 caps), and contain a summary of the error on the rest of the line. The
1516 remaining lines of the response body will be a python exception. The client
1517 application should look for the ERROR: and stop processing JSON as soon as
1518 it is seen. Note that neither a file being unrecoverable nor a directory
1519 merely being unhealthy will cause traversal to stop. The line just before
1520 the ERROR: will describe the directory that was untraversable, since the
1521 unit is emitted to the HTTP response body before the child is traversed.
1524 ``POST $URL?t=check&repair=true``
1526 This performs a health check of the given file or directory, and if the
1527 checker determines that the object is not healthy (some shares are missing
1528 or corrupted), it will perform a "repair". During repair, any missing
1529 shares will be regenerated and uploaded to new servers.
1531 This accepts the same verify=true and add-lease= arguments as t=check. When
1532 an output=JSON argument is provided, the machine-readable JSON response
1533 will contain the following keys::
1535 storage-index: a base32-encoded string with the objects's storage index,
1536 or an empty string for LIT files
1537 repair-attempted: (bool) True if repair was attempted
1538 repair-successful: (bool) True if repair was attempted and the file was
1539 fully healthy afterwards. False if no repair was
1540 attempted, or if a repair attempt failed.
1541 pre-repair-results: a dictionary that describes the state of the file
1542 before any repair was performed. This contains exactly
1543 the same keys as the 'results' value of the t=check
1544 response, described above.
1545 post-repair-results: a dictionary that describes the state of the file
1546 after any repair was performed. If no repair was
1547 performed, post-repair-results and pre-repair-results
1548 will be the same. This contains exactly the same keys
1549 as the 'results' value of the t=check response,
1552 ``POST $URL?t=start-deep-check&repair=true`` (must add &ophandle=XYZ)
1554 This triggers a recursive walk of all files and directories, performing a
1555 t=check&repair=true on each one.
1557 Like t=start-deep-check without the repair= argument, this can only be
1558 invoked on a directory. An error (400 BAD_REQUEST) will be signalled if it
1559 is invoked on a file. The recursive walker will deal with loops safely.
1561 This accepts the same verify= and add-lease= arguments as
1562 t=start-deep-check. It uses the same ophandle= mechanism as
1563 start-deep-check. When an output=JSON argument is provided, the response
1564 will contain the following keys::
1566 finished: (bool) True if the operation has completed, else False
1567 root-storage-index: a base32-encoded string with the storage index of the
1568 starting point of the deep-check operation
1569 count-objects-checked: count of how many objects were checked
1571 count-objects-healthy-pre-repair: how many of those objects were completely
1572 healthy, before any repair
1573 count-objects-unhealthy-pre-repair: how many were damaged in some way
1574 count-objects-healthy-post-repair: how many of those objects were completely
1575 healthy, after any repair
1576 count-objects-unhealthy-post-repair: how many were damaged in some way
1578 count-repairs-attempted: repairs were attempted on this many objects.
1579 count-repairs-successful: how many repairs resulted in healthy objects
1580 count-repairs-unsuccessful: how many repairs resulted did not results in
1581 completely healthy objects
1582 count-corrupt-shares-pre-repair: how many shares were found to have
1583 corruption, summed over all objects
1584 examined, before any repair
1585 count-corrupt-shares-post-repair: how many shares were found to have
1586 corruption, summed over all objects
1587 examined, after any repair
1588 list-corrupt-shares: a list of "share identifiers", one for each share
1589 that was found to be corrupt (before any repair).
1590 Each share identifier is a list of (serverid,
1591 storage_index, sharenum).
1592 list-remaining-corrupt-shares: like list-corrupt-shares, but mutable shares
1593 that were successfully repaired are not
1594 included. These are shares that need
1595 manual processing. Since immutable shares
1596 cannot be modified by clients, all corruption
1597 in immutable shares will be listed here.
1598 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1599 each file that was not fully healthy. 'pathname' is
1600 relative to the directory on which deep-check was
1601 invoked. The 'check-results' field is the same as
1602 that returned by t=check&repair=true&output=JSON,
1604 stats: a dictionary with the same keys as the t=start-deep-stats command
1607 ``POST $URL?t=stream-deep-check&repair=true``
1609 This triggers a recursive walk of all files and directories, performing a
1610 t=check&repair=true on each one. For each unique object (duplicates are
1611 skipped), a single line of JSON is emitted to the HTTP response channel (or
1612 an error indication). When the walk is complete, a final line of JSON is
1613 emitted which contains the accumulated file-size/count "deep-stats" data.
1615 This emits the same data as t=stream-deep-check (without the repair=true),
1616 except that the "check-results" field is replaced with a
1617 "check-and-repair-results" field, which contains the keys returned by
1618 t=check&repair=true&output=json (i.e. repair-attempted, repair-successful,
1619 pre-repair-results, and post-repair-results). The output does not contain
1620 the summary dictionary that is provied by t=start-deep-check&repair=true
1621 (the one with count-objects-checked and list-unhealthy-files), since the
1622 receiving client is expected to calculate those values itself from the
1623 stream of per-object check-and-repair-results.
1625 Note that the "ERROR:" indication will only be emitted if traversal stops,
1626 which will only occur if an unrecoverable directory is encountered. If a
1627 file or directory repair fails, the traversal will continue, and the repair
1628 failure will be indicated in the JSON data (in the "repair-successful" key).
1630 ``POST $DIRURL?t=start-manifest`` (must add &ophandle=XYZ)
1632 This operation generates a "manfest" of the given directory tree, mostly
1633 for debugging. This is a table of (path, filecap/dircap), for every object
1634 reachable from the starting directory. The path will be slash-joined, and
1635 the filecap/dircap will contain a link to the object in question. This page
1636 gives immediate access to every object in the virtual filesystem subtree.
1638 This operation uses the same ophandle= mechanism as deep-check. The
1639 corresponding /operations/$HANDLE page has three different forms. The
1640 default is output=HTML.
1642 If output=text is added to the query args, the results will be a text/plain
1643 list. The first line is special: it is either "finished: yes" or "finished:
1644 no"; if the operation is not finished, you must periodically reload the
1645 page until it completes. The rest of the results are a plaintext list, with
1646 one file/dir per line, slash-separated, with the filecap/dircap separated
1649 If output=JSON is added to the queryargs, then the results will be a
1650 JSON-formatted dictionary with six keys. Note that because large directory
1651 structures can result in very large JSON results, the full results will not
1652 be available until the operation is complete (i.e. until output["finished"]
1655 finished (bool): if False then you must reload the page until True
1656 origin_si (base32 str): the storage index of the starting point
1657 manifest: list of (path, cap) tuples, where path is a list of strings.
1658 verifycaps: list of (printable) verify cap strings
1659 storage-index: list of (base32) storage index strings
1660 stats: a dictionary with the same keys as the t=start-deep-stats command
1663 ``POST $DIRURL?t=start-deep-size`` (must add &ophandle=XYZ)
1665 This operation generates a number (in bytes) containing the sum of the
1666 filesize of all directories and immutable files reachable from the given
1667 directory. This is a rough lower bound of the total space consumed by this
1668 subtree. It does not include space consumed by mutable files, nor does it
1669 take expansion or encoding overhead into account. Later versions of the
1670 code may improve this estimate upwards.
1672 The /operations/$HANDLE status output consists of two lines of text::
1677 ``POST $DIRURL?t=start-deep-stats`` (must add &ophandle=XYZ)
1679 This operation performs a recursive walk of all files and directories
1680 reachable from the given directory, and generates a collection of
1681 statistics about those objects.
1683 The result (obtained from the /operations/$OPHANDLE page) is a
1684 JSON-serialized dictionary with the following keys (note that some of these
1685 keys may be missing until 'finished' is True)::
1687 finished: (bool) True if the operation has finished, else False
1688 count-immutable-files: count of how many CHK files are in the set
1689 count-mutable-files: same, for mutable files (does not include directories)
1690 count-literal-files: same, for LIT files (data contained inside the URI)
1691 count-files: sum of the above three
1692 count-directories: count of directories
1693 count-unknown: count of unrecognized objects (perhaps from the future)
1694 size-immutable-files: total bytes for all CHK files in the set, =deep-size
1695 size-mutable-files (TODO): same, for current version of all mutable files
1696 size-literal-files: same, for LIT files
1697 size-directories: size of directories (includes size-literal-files)
1698 size-files-histogram: list of (minsize, maxsize, count) buckets,
1699 with a histogram of filesizes, 5dB/bucket,
1700 for both literal and immutable files
1701 largest-directory: number of children in the largest directory
1702 largest-immutable-file: number of bytes in the largest CHK file
1704 size-mutable-files is not implemented, because it would require extra
1705 queries to each mutable file to get their size. This may be implemented in
1708 Assuming no sharing, the basic space consumed by a single root directory is
1709 the sum of size-immutable-files, size-mutable-files, and size-directories.
1710 The actual disk space used by the shares is larger, because of the
1711 following sources of overhead::
1714 expansion due to erasure coding
1715 share management data (leases)
1716 backend (ext3) minimum block size
1718 ``POST $URL?t=stream-manifest``
1720 This operation performs a recursive walk of all files and directories
1721 reachable from the given starting point. For each such unique object
1722 (duplicates are skipped), a single line of JSON is emitted to the HTTP
1723 response channel (or an error indication, see below). When the walk is
1724 complete, a final line of JSON is emitted which contains the accumulated
1725 file-size/count "deep-stats" data.
1727 A CLI tool can split the response stream on newlines into "response units",
1728 and parse each response unit as JSON. Each such parsed unit will be a
1729 dictionary, and will contain at least the "type" key: a string, one of
1730 "file", "directory", or "stats".
1732 For all units that have a type of "file" or "directory", the dictionary will
1733 contain the following keys::
1735 "path": a list of strings, with the path that is traversed to reach the
1737 "cap": a write-cap URI for the file or directory, if available, else a
1739 "verifycap": a verify-cap URI for the file or directory
1740 "repaircap": an URI for the weakest cap that can still be used to repair
1742 "storage-index": a base32 storage index for the object
1744 Note that non-distributed files (i.e. LIT files) will have values of None
1745 for verifycap, repaircap, and storage-index, since these files can neither
1746 be verified nor repaired, and are not stored on the storage servers.
1748 The last unit in the stream will have a type of "stats", and will contain
1749 the keys described in the "start-deep-stats" operation, below.
1751 If any errors occur during the traversal (specifically if a directory is
1752 unrecoverable, such that further traversal is not possible), an error
1753 indication is written to the response body, instead of the usual line of
1754 JSON. This error indication line will begin with the string "ERROR:" (in all
1755 caps), and contain a summary of the error on the rest of the line. The
1756 remaining lines of the response body will be a python exception. The client
1757 application should look for the ERROR: and stop processing JSON as soon as
1758 it is seen. The line just before the ERROR: will describe the directory that
1759 was untraversable, since the manifest entry is emitted to the HTTP response
1760 body before the child is traversed.
1766 The portion of the web namespace that begins with "/uri" (and "/named") is
1767 dedicated to giving users (both humans and programs) access to the Tahoe
1768 virtual filesystem. The rest of the namespace provides status information
1769 about the state of the Tahoe node.
1771 ``GET /`` (the root page)
1773 This is the "Welcome Page", and contains a few distinct sections::
1775 Node information: library versions, local nodeid, services being provided.
1777 Filesystem Access Forms: create a new directory, view a file/directory by
1778 URI, upload a file (unlinked), download a file by
1781 Grid Status: introducer information, helper information, connected storage
1786 This page lists all active uploads and downloads, and contains a short list
1787 of recent upload/download operations. Each operation has a link to a page
1788 that describes file sizes, servers that were involved, and the time consumed
1789 in each phase of the operation.
1791 A GET of /status/?t=json will contain a machine-readable subset of the same
1792 data. It returns a JSON-encoded dictionary. The only key defined at this
1793 time is "active", with a value that is a list of operation dictionaries, one
1794 for each active operation. Once an operation is completed, it will no longer
1795 appear in data["active"] .
1797 Each op-dict contains a "type" key, one of "upload", "download",
1798 "mapupdate", "publish", or "retrieve" (the first two are for immutable
1799 files, while the latter three are for mutable files and directories).
1801 The "upload" op-dict will contain the following keys::
1803 type (string): "upload"
1804 storage-index-string (string): a base32-encoded storage index
1805 total-size (int): total size of the file
1806 status (string): current status of the operation
1807 progress-hash (float): 1.0 when the file has been hashed
1808 progress-ciphertext (float): 1.0 when the file has been encrypted.
1809 progress-encode-push (float): 1.0 when the file has been encoded and
1810 pushed to the storage servers. For helper
1811 uploads, the ciphertext value climbs to 1.0
1812 first, then encoding starts. For unassisted
1813 uploads, ciphertext and encode-push progress
1814 will climb at the same pace.
1816 The "download" op-dict will contain the following keys::
1818 type (string): "download"
1819 storage-index-string (string): a base32-encoded storage index
1820 total-size (int): total size of the file
1821 status (string): current status of the operation
1822 progress (float): 1.0 when the file has been fully downloaded
1824 Front-ends which want to report progress information are advised to simply
1825 average together all the progress-* indicators. A slightly more accurate
1826 value can be found by ignoring the progress-hash value (since the current
1827 implementation hashes synchronously, so clients will probably never see
1828 progress-hash!=1.0).
1830 ``GET /helper_status/``
1832 If the node is running a helper (i.e. if [helper]enabled is set to True in
1833 tahoe.cfg), then this page will provide a list of all the helper operations
1834 currently in progress. If "?t=json" is added to the URL, it will return a
1835 JSON-formatted list of helper statistics, which can then be used to produce
1836 graphs to indicate how busy the helper is.
1838 ``GET /statistics/``
1840 This page provides "node statistics", which are collected from a variety of
1843 load_monitor: every second, the node schedules a timer for one second in
1844 the future, then measures how late the subsequent callback
1845 is. The "load_average" is this tardiness, measured in
1846 seconds, averaged over the last minute. It is an indication
1847 of a busy node, one which is doing more work than can be
1848 completed in a timely fashion. The "max_load" value is the
1849 highest value that has been seen in the last 60 seconds.
1851 cpu_monitor: every minute, the node uses time.clock() to measure how much
1852 CPU time it has used, and it uses this value to produce
1853 1min/5min/15min moving averages. These values range from 0%
1854 (0.0) to 100% (1.0), and indicate what fraction of the CPU
1855 has been used by the Tahoe node. Not all operating systems
1856 provide meaningful data to time.clock(): they may report 100%
1857 CPU usage at all times.
1859 uploader: this counts how many immutable files (and bytes) have been
1860 uploaded since the node was started
1862 downloader: this counts how many immutable files have been downloaded
1863 since the node was started
1865 publishes: this counts how many mutable files (including directories) have
1866 been modified since the node was started
1868 retrieves: this counts how many mutable files (including directories) have
1869 been read since the node was started
1871 There are other statistics that are tracked by the node. The "raw stats"
1872 section shows a formatted dump of all of them.
1874 By adding "?t=json" to the URL, the node will return a JSON-formatted
1875 dictionary of stats values, which can be used by other tools to produce
1876 graphs of node behavior. The misc/munin/ directory in the source
1877 distribution provides some tools to produce these graphs.
1879 ``GET /`` (introducer status)
1881 For Introducer nodes, the welcome page displays information about both
1882 clients and servers which are connected to the introducer. Servers make
1883 "service announcements", and these are listed in a table. Clients will
1884 subscribe to hear about service announcements, and these subscriptions are
1885 listed in a separate table. Both tables contain information about what
1886 version of Tahoe is being run by the remote node, their advertised and
1887 outbound IP addresses, their nodeid and nickname, and how long they have
1890 By adding "?t=json" to the URL, the node will return a JSON-formatted
1891 dictionary of stats values, which can be used to produce graphs of connected
1892 clients over time. This dictionary has the following keys::
1894 ["subscription_summary"] : a dictionary mapping service name (like
1895 "storage") to an integer with the number of
1896 clients that have subscribed to hear about that
1898 ["announcement_summary"] : a dictionary mapping service name to an integer
1899 with the number of servers which are announcing
1901 ["announcement_distinct_hosts"] : a dictionary mapping service name to an
1902 integer which represents the number of
1903 distinct hosts that are providing that
1904 service. If two servers have announced
1905 FURLs which use the same hostnames (but
1906 different ports and tubids), they are
1907 considered to be on the same host.
1910 Static Files in /public_html
1911 ============================
1913 The web-API server will take any request for a URL that starts with /static
1914 and serve it from a configurable directory which defaults to
1915 $BASEDIR/public_html . This is configured by setting the "[node]web.static"
1916 value in $BASEDIR/tahoe.cfg . If this is left at the default value of
1917 "public_html", then http://127.0.0.1:3456/static/subdir/foo.html will be
1918 served with the contents of the file $BASEDIR/public_html/subdir/foo.html .
1920 This can be useful to serve a javascript application which provides a
1921 prettier front-end to the rest of the Tahoe web-API.
1924 Safety and Security Issues -- Names vs. URIs
1925 ============================================
1927 Summary: use explicit file- and dir- caps whenever possible, to reduce the
1928 potential for surprises when the filesystem structure is changed.
1930 Tahoe provides a mutable filesystem, but the ways that the filesystem can
1931 change are limited. The only thing that can change is that the mapping from
1932 child names to child objects that each directory contains can be changed by
1933 adding a new child name pointing to an object, removing an existing child name,
1934 or changing an existing child name to point to a different object.
1936 Obviously if you query Tahoe for information about the filesystem and then act
1937 to change the filesystem (such as by getting a listing of the contents of a
1938 directory and then adding a file to the directory), then the filesystem might
1939 have been changed after you queried it and before you acted upon it. However,
1940 if you use the URI instead of the pathname of an object when you act upon the
1941 object, then the only change that can happen is if the object is a directory
1942 then the set of child names it has might be different. If, on the other hand,
1943 you act upon the object using its pathname, then a different object might be in
1944 that place, which can result in more kinds of surprises.
1946 For example, suppose you are writing code which recursively downloads the
1947 contents of a directory. The first thing your code does is fetch the listing
1948 of the contents of the directory. For each child that it fetched, if that
1949 child is a file then it downloads the file, and if that child is a directory
1950 then it recurses into that directory. Now, if the download and the recurse
1951 actions are performed using the child's name, then the results might be
1952 wrong, because for example a child name that pointed to a sub-directory when
1953 you listed the directory might have been changed to point to a file (in which
1954 case your attempt to recurse into it would result in an error and the file
1955 would be skipped), or a child name that pointed to a file when you listed the
1956 directory might now point to a sub-directory (in which case your attempt to
1957 download the child would result in a file containing HTML text describing the
1960 If your recursive algorithm uses the uri of the child instead of the name of
1961 the child, then those kinds of mistakes just can't happen. Note that both the
1962 child's name and the child's URI are included in the results of listing the
1963 parent directory, so it isn't any harder to use the URI for this purpose.
1965 The read and write caps in a given directory node are separate URIs, and
1966 can't be assumed to point to the same object even if they were retrieved in
1967 the same operation (although the web-API server attempts to ensure this
1968 in most cases). If you need to rely on that property, you should explicitly
1969 verify it. More generally, you should not make assumptions about the
1970 internal consistency of the contents of mutable directories. As a result
1971 of the signatures on mutable object versions, it is guaranteed that a given
1972 version was written in a single update, but -- as in the case of a file --
1973 the contents may have been chosen by a malicious writer in a way that is
1974 designed to confuse applications that rely on their consistency.
1976 In general, use names if you want "whatever object (whether file or
1977 directory) is found by following this name (or sequence of names) when my
1978 request reaches the server". Use URIs if you want "this particular object".
1984 Tahoe uses both mutable and immutable files. Mutable files can be created
1985 explicitly by doing an upload with ?mutable=true added, or implicitly by
1986 creating a new directory (since a directory is just a special way to
1987 interpret a given mutable file).
1989 Mutable files suffer from the same consistency-vs-availability tradeoff that
1990 all distributed data storage systems face. It is not possible to
1991 simultaneously achieve perfect consistency and perfect availability in the
1992 face of network partitions (servers being unreachable or faulty).
1994 Tahoe tries to achieve a reasonable compromise, but there is a basic rule in
1995 place, known as the Prime Coordination Directive: "Don't Do That". What this
1996 means is that if write-access to a mutable file is available to several
1997 parties, then those parties are responsible for coordinating their activities
1998 to avoid multiple simultaneous updates. This could be achieved by having
1999 these parties talk to each other and using some sort of locking mechanism, or
2000 by serializing all changes through a single writer.
2002 The consequences of performing uncoordinated writes can vary. Some of the
2003 writers may lose their changes, as somebody else wins the race condition. In
2004 many cases the file will be left in an "unhealthy" state, meaning that there
2005 are not as many redundant shares as we would like (reducing the reliability
2006 of the file against server failures). In the worst case, the file can be left
2007 in such an unhealthy state that no version is recoverable, even the old ones.
2008 It is this small possibility of data loss that prompts us to issue the Prime
2009 Coordination Directive.
2011 Tahoe nodes implement internal serialization to make sure that a single Tahoe
2012 node cannot conflict with itself. For example, it is safe to issue two
2013 directory modification requests to a single tahoe node's web-API server at the
2014 same time, because the Tahoe node will internally delay one of them until
2015 after the other has finished being applied. (This feature was introduced in
2016 Tahoe-1.1; back with Tahoe-1.0 the web client was responsible for serializing
2017 web requests themselves).
2019 For more details, please see the "Consistency vs Availability" and "The Prime
2020 Coordination Directive" sections of `mutable.rst <../specifications/mutable.rst>`_.
2026 Gateway nodes may find it necessary to prohibit access to certain files. The
2027 web-API has a facility to block access to filecaps by their storage index,
2028 returning a 403 "Forbidden" error instead of the original file.
2030 This blacklist is recorded in $NODEDIR/access.blacklist, and contains one
2031 blocked file per line. Comment lines (starting with ``#``) are ignored. Each
2032 line consists of the storage-index (in the usual base32 format as displayed
2033 by the "More Info" page, or by the "tahoe debug dump-cap" command), followed
2034 by whitespace, followed by a reason string, which will be included in the 403
2035 error message. This could hold a URL to a page that explains why the file is
2036 blocked, for example.
2038 So for example, if you found a need to block access to a file with filecap
2039 ``URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861``,
2040 you could do the following::
2042 tahoe debug dump-cap URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2043 -> storage index: whpepioyrnff7orecjolvbudeu
2044 echo "whpepioyrnff7orecjolvbudeu my puppy told me to" >>$NODEDIR/access.blacklist
2045 tahoe restart $NODEDIR
2046 tahoe get URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2047 -> error, 403 Access Prohibited: my puppy told me to
2049 The ``access.blacklist`` file will be checked each time a file or directory
2050 is accessed: the file's ``mtime`` is used to decide whether it need to be
2051 reloaded. Therefore no node restart is necessary when creating the initial
2052 blacklist, nor when adding second, third, or additional entries to the list.
2053 When modifying the file, be careful to update it atomically, otherwise a
2054 request may arrive while the file is only halfway written, and the partial
2055 file may be incorrectly parsed.
2057 The blacklist is applied to all access paths (including SFTP, FTP, and CLI
2058 operations), not just the web-API. The blacklist also applies to directories.
2059 If a directory is blacklisted, the gateway will refuse access to both that
2060 directory and any child files/directories underneath it, when accessed via
2061 "DIRCAP/SUBDIR/FILENAME" -style URLs. Users who go directly to the child
2062 file/dir will bypass the blacklist.
2064 The node will log the SI of the file being blocked, and the reason code, into
2065 the ``logs/twistd.log`` file.
2068 .. [1] URLs and HTTP and UTF-8, Oh My
2070 HTTP does not provide a mechanism to specify the character set used to
2071 encode non-ASCII names in URLs
2072 (`RFC3986#2.1 <https://tools.ietf.org/html/rfc3986#section-2.1>`_).
2073 We prefer the convention that the ``filename=`` argument shall be a
2074 URL-escaped UTF-8 encoded Unicode string.
2075 For example, suppose we want to provoke the server into using a filename of
2076 "f i a n c e-acute e" (i.e. f i a n c U+00E9 e). The UTF-8 encoding of this
2077 is 0x66 0x69 0x61 0x6e 0x63 0xc3 0xa9 0x65 (or "fianc\\xC3\\xA9e", as python's
2078 ``repr()`` function would show). To encode this into a URL, the non-printable
2079 characters must be escaped with the urlencode ``%XX`` mechanism, giving
2080 us "fianc%C3%A9e". Thus, the first line of the HTTP request will be
2081 "``GET /uri/CAP...?save=true&filename=fianc%C3%A9e HTTP/1.1``". Not all
2082 browsers provide this: IE7 by default uses the Latin-1 encoding, which is
2083 "fianc%E9e" (although it has a configuration option to send URLs as UTF-8).
2085 The response header will need to indicate a non-ASCII filename. The actual
2086 mechanism to do this is not clear. For ASCII filenames, the response header
2089 Content-Disposition: attachment; filename="english.txt"
2091 If Tahoe were to enforce the UTF-8 convention, it would need to decode the
2092 URL argument into a Unicode string, and then encode it back into a sequence
2093 of bytes when creating the response header. One possibility would be to use
2094 unencoded UTF-8. Developers suggest that IE7 might accept this::
2096 #1: Content-Disposition: attachment; filename="fianc\xC3\xA9e"
2097 (note, the last four bytes of that line, not including the newline, are
2098 0xC3 0xA9 0x65 0x22)
2100 `RFC2231#4 <https://tools.ietf.org/html/rfc2231#section-4>`_
2101 (dated 1997): suggests that the following might work, and
2102 `some developers have reported <http://markmail.org/message/dsjyokgl7hv64ig3>`_
2103 that it is supported by Firefox (but not IE7)::
2105 #2: Content-Disposition: attachment; filename*=utf-8''fianc%C3%A9e
2107 My reading of `RFC2616#19.5.1 <https://tools.ietf.org/html/rfc2616#section-19.5.1>`_
2108 (which defines Content-Disposition) says that the filename= parameter is
2109 defined to be wrapped in quotes (presumably to allow spaces without breaking
2110 the parsing of subsequent parameters), which would give us::
2112 #3: Content-Disposition: attachment; filename*=utf-8''"fianc%C3%A9e"
2114 However this is contrary to the examples in the email thread listed above.
2116 Developers report that IE7 (when it is configured for UTF-8 URL encoding,
2117 which is not the default in Asian countries), will accept::
2119 #4: Content-Disposition: attachment; filename=fianc%C3%A9e
2121 However, for maximum compatibility, Tahoe simply copies bytes from the URL
2122 into the response header, rather than enforcing the UTF-8 convention. This
2123 means it does not try to decode the filename from the URL argument, nor does
2124 it encode the filename into the response header.