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. `Debugging and Testing Features`_
35 7. `Other Useful Pages`_
36 8. `Static Files in /public_html`_
37 9. `Safety and Security Issues -- Names vs. URIs`_
38 10. `Concurrency Issues`_
39 11. `Access Blacklist`_
42 Enabling the web-API port
43 =========================
45 Every Tahoe node is capable of running a built-in HTTP server. To enable
46 this, just write a port number into the "[node]web.port" line of your node's
47 tahoe.cfg file. For example, writing "web.port = 3456" into the "[node]"
48 section of $NODEDIR/tahoe.cfg will cause the node to run a webserver on port
51 This string is actually a Twisted "strports" specification, meaning you can
52 get more control over the interface to which the server binds by supplying
53 additional arguments. For more details, see the documentation on
54 `twisted.application.strports
55 <http://twistedmatrix.com/documents/current/api/twisted.application.strports.html>`_.
57 Writing "tcp:3456:interface=127.0.0.1" into the web.port line does the same
58 but binds to the loopback interface, ensuring that only the programs on the
59 local host can connect. Using "ssl:3456:privateKey=mykey.pem:certKey=cert.pem"
62 This webport can be set when the node is created by passing a --webport
63 option to the 'tahoe create-node' command. By default, the node listens on
64 port 3456, on the loopback (127.0.0.1) interface.
67 Basic Concepts: GET, PUT, DELETE, POST
68 ======================================
70 As described in `docs/architecture.rst <../architecture.rst>`_, each file
71 and directory in a Tahoe virtual filesystem is referenced by an identifier
72 that combines the designation of the object with the authority to do something
73 with it (such as read or modify the contents). This identifier is called a
74 "read-cap" or "write-cap", depending upon whether it enables read-only or
75 read-write access. These "caps" are also referred to as URIs (which may be
76 confusing because they are not currently `RFC3986
77 <http://tools.ietf.org/html/rfc3986>`_-compliant URIs).
79 The Tahoe web-based API is "REST-ful", meaning it implements the concepts of
80 "REpresentational State Transfer": the original scheme by which the World
81 Wide Web was intended to work. Each object (file or directory) is referenced
82 by a URL that includes the read- or write- cap. HTTP methods (GET, PUT, and
83 DELETE) are used to manipulate these objects. You can think of the URL as a
84 noun, and the method as a verb.
86 In REST, the GET method is used to retrieve information about an object, or
87 to retrieve some representation of the object itself. When the object is a
88 file, the basic GET method will simply return the contents of that file.
89 Other variations (generally implemented by adding query parameters to the
90 URL) will return information about the object, such as metadata. GET
91 operations are required to have no side-effects.
93 PUT is used to upload new objects into the filesystem, or to replace an
94 existing link or the contents of a mutable file. DELETE is used to unlink
95 objects from directories. Both PUT and DELETE are required to be idempotent:
96 performing the same operation multiple times must have the same side-effects
97 as only performing it once.
99 POST is used for more complicated actions that cannot be expressed as a GET,
100 PUT, or DELETE. POST operations can be thought of as a method call: sending
101 some message to the object referenced by the URL. In Tahoe, POST is also used
102 for operations that must be triggered by an HTML form (including upload and
103 unlinking), because otherwise a regular web browser has no way to accomplish
104 these tasks. In general, everything that can be done with a PUT or DELETE can
105 also be done with a POST.
107 Tahoe's web API is designed for two different kinds of consumer. The first is
108 a program that needs to manipulate the virtual file system. Such programs are
109 expected to use the RESTful interface described above. The second is a human
110 using a standard web browser to work with the filesystem. This user is given
111 a series of HTML pages with links to download files, and forms that use POST
112 actions to upload, rename, and unlink files.
114 When an error occurs, the HTTP response code will be set to an appropriate
115 400-series code (like 404 Not Found for an unknown childname, or 400 Bad Request
116 when the parameters to a web-API operation are invalid), and the HTTP response
117 body will usually contain a few lines of explanation as to the cause of the
118 error and possible responses. Unusual exceptions may result in a 500 Internal
119 Server Error as a catch-all, with a default response body containing
120 a Nevow-generated HTML-ized representation of the Python exception stack trace
121 that caused the problem. CLI programs which want to copy the response body to
122 stderr should provide an "Accept: text/plain" header to their requests to get
123 a plain text stack trace instead. If the Accept header contains ``*/*``, or
124 ``text/*``, or text/html (or if there is no Accept header), HTML tracebacks will
131 Tahoe uses a variety of read- and write- caps to identify files and
132 directories. The most common of these is the "immutable file read-cap", which
133 is used for most uploaded files. These read-caps look like the following::
135 URI:CHK:ime6pvkaxuetdfah2p2f35pe54:4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a:3:10:202
137 The next most common is a "directory write-cap", which provides both read and
138 write access to a directory, and look like this::
140 URI:DIR2:djrdkfawoqihigoett4g6auz6a:jx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq
142 There are also "directory read-caps", which start with "URI:DIR2-RO:", and
143 give read-only access to a directory. Finally there are also mutable file
144 read- and write- caps, which start with "URI:SSK", and give access to mutable
147 (Later versions of Tahoe will make these strings shorter, and will remove the
148 unfortunate colons, which must be escaped when these caps are embedded in
151 To refer to any Tahoe object through the web API, you simply need to combine
152 a prefix (which indicates the HTTP server to use) with the cap (which
153 indicates which object inside that server to access). Since the default Tahoe
154 webport is 3456, the most common prefix is one that will use a local node
155 listening on this port::
157 http://127.0.0.1:3456/uri/ + $CAP
159 So, to access the directory named above (which happens to be the
160 publically-writeable sample directory on the Tahoe test grid, described at
161 http://allmydata.org/trac/tahoe/wiki/TestGrid), the URL would be::
163 http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/
165 (note that the colons in the directory-cap are url-encoded into "%3A"
168 Likewise, to access the file named above, use::
170 http://127.0.0.1:3456/uri/URI%3ACHK%3Aime6pvkaxuetdfah2p2f35pe54%3A4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a%3A3%3A10%3A202
172 In the rest of this document, we'll use "$DIRCAP" as shorthand for a read-cap
173 or write-cap that refers to a directory, and "$FILECAP" to abbreviate a cap
174 that refers to a file (whether mutable or immutable). So those URLs above can
177 http://127.0.0.1:3456/uri/$DIRCAP/
178 http://127.0.0.1:3456/uri/$FILECAP
180 The operation summaries below will abbreviate these further, by eliding the
181 server prefix. They will be displayed like this::
190 Tahoe directories contain named child entries, just like directories in a regular
191 local filesystem. These child entries, called "dirnodes", consist of a name,
192 metadata, a write slot, and a read slot. The write and read slots normally contain
193 a write-cap and read-cap referring to the same object, which can be either a file
194 or a subdirectory. The write slot may be empty (actually, both may be empty,
195 but that is unusual).
197 If you have a Tahoe URL that refers to a directory, and want to reference a
198 named child inside it, just append the child name to the URL. For example, if
199 our sample directory contains a file named "welcome.txt", we can refer to
202 http://127.0.0.1:3456/uri/$DIRCAP/welcome.txt
204 (or http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/welcome.txt)
206 Multiple levels of subdirectories can be handled this way::
208 http://127.0.0.1:3456/uri/$DIRCAP/tahoe-source/docs/architecture.rst
210 In this document, when we need to refer to a URL that references a file using
211 this child-of-some-directory format, we'll use the following string::
213 /uri/$DIRCAP/[SUBDIRS../]FILENAME
215 The "[SUBDIRS../]" part means that there are zero or more (optional)
216 subdirectory names in the middle of the URL. The "FILENAME" at the end means
217 that this whole URL refers to a file of some sort, rather than to a
220 When we need to refer specifically to a directory in this way, we'll write::
222 /uri/$DIRCAP/[SUBDIRS../]SUBDIR
225 Note that all components of pathnames in URLs are required to be UTF-8
226 encoded, so "resume.doc" (with an acute accent on both E's) would be accessed
229 http://127.0.0.1:3456/uri/$DIRCAP/r%C3%A9sum%C3%A9.doc
231 Also note that the filenames inside upload POST forms are interpreted using
232 whatever character set was provided in the conventional '_charset' field, and
233 defaults to UTF-8 if not otherwise specified. The JSON representation of each
234 directory contains native Unicode strings. Tahoe directories are specified to
235 contain Unicode filenames, and cannot contain binary strings that are not
236 representable as such.
238 All Tahoe operations that refer to existing files or directories must include
239 a suitable read- or write- cap in the URL: the web-API server won't add one
240 for you. If you don't know the cap, you can't access the file. This allows
241 the security properties of Tahoe caps to be extended across the web-API
245 Slow Operations, Progress, and Cancelling
246 =========================================
248 Certain operations can be expected to take a long time. The "t=deep-check",
249 described below, will recursively visit every file and directory reachable
250 from a given starting point, which can take minutes or even hours for
251 extremely large directory structures. A single long-running HTTP request is a
252 fragile thing: proxies, NAT boxes, browsers, and users may all grow impatient
253 with waiting and give up on the connection.
255 For this reason, long-running operations have an "operation handle", which
256 can be used to poll for status/progress messages while the operation
257 proceeds. This handle can also be used to cancel the operation. These handles
258 are created by the client, and passed in as a an "ophandle=" query argument
259 to the POST or PUT request which starts the operation. The following
260 operations can then be used to retrieve status:
262 ``GET /operations/$HANDLE?output=HTML (with or without t=status)``
264 ``GET /operations/$HANDLE?output=JSON (same)``
266 These two retrieve the current status of the given operation. Each operation
267 presents a different sort of information, but in general the page retrieved
270 * whether the operation is complete, or if it is still running
271 * how much of the operation is complete, and how much is left, if possible
273 Note that the final status output can be quite large: a deep-manifest of a
274 directory structure with 300k directories and 200k unique files is about
275 275MB of JSON, and might take two minutes to generate. For this reason, the
276 full status is not provided until the operation has completed.
278 The HTML form will include a meta-refresh tag, which will cause a regular
279 web browser to reload the status page about 60 seconds later. This tag will
280 be removed once the operation has completed.
282 There may be more status information available under
283 /operations/$HANDLE/$ETC : i.e., the handle forms the root of a URL space.
285 ``POST /operations/$HANDLE?t=cancel``
287 This terminates the operation, and returns an HTML page explaining what was
288 cancelled. If the operation handle has already expired (see below), this
289 POST will return a 404, which indicates that the operation is no longer
290 running (either it was completed or terminated). The response body will be
291 the same as a GET /operations/$HANDLE on this operation handle, and the
292 handle will be expired immediately afterwards.
294 The operation handle will eventually expire, to avoid consuming an unbounded
295 amount of memory. The handle's time-to-live can be reset at any time, by
296 passing a retain-for= argument (with a count of seconds) to either the
297 initial POST that starts the operation, or the subsequent GET request which
298 asks about the operation. For example, if a 'GET
299 /operations/$HANDLE?output=JSON&retain-for=600' query is performed, the
300 handle will remain active for 600 seconds (10 minutes) after the GET was
303 In addition, if the GET includes a release-after-complete=True argument, and
304 the operation has completed, the operation handle will be released
307 If a retain-for= argument is not used, the default handle lifetimes are:
309 * handles will remain valid at least until their operation finishes
310 * uncollected handles for finished operations (i.e. handles for
311 operations that have finished but for which the GET page has not been
312 accessed since completion) will remain valid for four days, or for
313 the total time consumed by the operation, whichever is greater.
314 * collected handles (i.e. the GET page has been retrieved at least once
315 since the operation completed) will remain valid for one day.
317 Many "slow" operations can begin to use unacceptable amounts of memory when
318 operating on large directory structures. The memory usage increases when the
319 ophandle is polled, as the results must be copied into a JSON string, sent
320 over the wire, then parsed by a client. So, as an alternative, many "slow"
321 operations have streaming equivalents. These equivalents do not use operation
322 handles. Instead, they emit line-oriented status results immediately. Client
323 code can cancel the operation by simply closing the HTTP connection.
326 Programmatic Operations
327 =======================
329 Now that we know how to build URLs that refer to files and directories in a
330 Tahoe virtual filesystem, what sorts of operations can we do with those URLs?
331 This section contains a catalog of GET, PUT, DELETE, and POST operations that
332 can be performed on these URLs. This set of operations are aimed at programs
333 that use HTTP to communicate with a Tahoe node. A later section describes
334 operations that are intended for web browsers.
340 ``GET /uri/$FILECAP``
342 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME``
344 This will retrieve the contents of the given file. The HTTP response body
345 will contain the sequence of bytes that make up the file.
347 To view files in a web browser, you may want more control over the
348 Content-Type and Content-Disposition headers. Please see the next section
349 "Browser Operations", for details on how to modify these URLs for that
353 Writing/Uploading A File
354 ------------------------
356 ``PUT /uri/$FILECAP``
358 ``PUT /uri/$DIRCAP/[SUBDIRS../]FILENAME``
360 Upload a file, using the data from the HTTP request body, and add whatever
361 child links and subdirectories are necessary to make the file available at
362 the given location. Once this operation succeeds, a GET on the same URL will
363 retrieve the same contents that were just uploaded. This will create any
364 necessary intermediate subdirectories.
366 To use the /uri/$FILECAP form, $FILECAP must be a write-cap for a mutable file.
368 In the /uri/$DIRCAP/[SUBDIRS../]FILENAME form, if the target file is a
369 writeable mutable file, that file's contents will be overwritten
370 in-place. If it is a read-cap for a mutable file, an error will occur.
371 If it is an immutable file, the old file will be discarded, and a new
372 one will be put in its place. If the target file is a writable mutable
373 file, you may also specify an "offset" parameter -- a byte offset that
374 determines where in the mutable file the data from the HTTP request
375 body is placed. This operation is relatively efficient for MDMF mutable
376 files, and is relatively inefficient (but still supported) for SDMF
377 mutable files. If no offset parameter is specified, then the entire
378 file is replaced with the data from the HTTP request body. For an
379 immutable file, the "offset" parameter is not valid.
381 When creating a new file, you can control the type of file created by
382 specifying a format= argument in the query string. format=MDMF creates an
383 MDMF mutable file. format=SDMF creates an SDMF mutable file. format=CHK
384 creates an immutable file. The value of the format argument is
385 case-insensitive. If no format is specified, the newly-created file will be
386 immutable (but see below).
388 For compatibility with previous versions of Tahoe-LAFS, the web-API will
389 also accept a mutable=true argument in the query string. If mutable=true is
390 given, then the new file will be mutable, and its format will be the default
391 mutable file format, as configured by the [client]mutable.format option of
392 tahoe.cfg on the Tahoe-LAFS node hosting the webapi server. Use of
393 mutable=true is discouraged; new code should use format= instead of
394 mutable=true (unless it needs to be compatible with web-API servers older
395 than v1.9.0). If neither format= nor mutable=true are given, the
396 newly-created file will be immutable.
398 This returns the file-cap of the resulting file. If a new file was created
399 by this method, the HTTP response code (as dictated by rfc2616) will be set
400 to 201 CREATED. If an existing file was replaced or modified, the response
403 Note that the 'curl -T localfile http://127.0.0.1:3456/uri/$DIRCAP/foo.txt'
404 command can be used to invoke this operation.
408 This uploads a file, and produces a file-cap for the contents, but does not
409 attach the file into the filesystem. No directories will be modified by
410 this operation. The file-cap is returned as the body of the HTTP response.
412 This method accepts format= and mutable=true as query string arguments, and
413 interprets those arguments in the same way as the linked forms of PUT
414 described immediately above.
416 Creating A New Directory
417 ------------------------
419 ``POST /uri?t=mkdir``
423 Create a new empty directory and return its write-cap as the HTTP response
424 body. This does not make the newly created directory visible from the
425 filesystem. The "PUT" operation is provided for backwards compatibility:
426 new code should use POST.
428 This supports a format= argument in the query string. The format=
429 argument, if specified, controls the format of the directory. format=MDMF
430 indicates that the directory should be stored as an MDMF file; format=SDMF
431 indicates that the directory should be stored as an SDMF file. The value of
432 the format= argument is case-insensitive. If no format= argument is
433 given, the directory's format is determined by the default mutable file
434 format, as configured on the Tahoe-LAFS node responding to the request.
436 ``POST /uri?t=mkdir-with-children``
438 Create a new directory, populated with a set of child nodes, and return its
439 write-cap as the HTTP response body. The new directory is not attached to
440 any other directory: the returned write-cap is the only reference to it.
442 The format of the directory can be controlled with the format= argument in
443 the query string, as described above.
445 Initial children are provided as the body of the POST form (this is more
446 efficient than doing separate mkdir and set_children operations). If the
447 body is empty, the new directory will be empty. If not empty, the body will
448 be interpreted as a UTF-8 JSON-encoded dictionary of children with which the
449 new directory should be populated, using the same format as would be
450 returned in the 'children' value of the t=json GET request, described below.
451 Each dictionary key should be a child name, and each value should be a list
452 of [TYPE, PROPDICT], where PROPDICT contains "rw_uri", "ro_uri", and
453 "metadata" keys (all others are ignored). For example, the PUT request body
457 "Fran\u00e7ais": [ "filenode", {
458 "ro_uri": "URI:CHK:...",
461 "ctime": 1202777696.7564139,
462 "mtime": 1202777696.7564139,
464 "linkcrtime": 1202777696.7564139,
465 "linkmotime": 1202777696.7564139
467 "subdir": [ "dirnode", {
468 "rw_uri": "URI:DIR2:...",
469 "ro_uri": "URI:DIR2-RO:...",
471 "ctime": 1202778102.7589991,
472 "mtime": 1202778111.2160511,
474 "linkcrtime": 1202777696.7564139,
475 "linkmotime": 1202777696.7564139
479 For forward-compatibility, a mutable directory can also contain caps in
480 a format that is unknown to the web-API server. When such caps are retrieved
481 from a mutable directory in a "ro_uri" field, they will be prefixed with
482 the string "ro.", indicating that they must not be decoded without
483 checking that they are read-only. The "ro." prefix must not be stripped
484 off without performing this check. (Future versions of the web-API server
485 will perform it where necessary.)
487 If both the "rw_uri" and "ro_uri" fields are present in a given PROPDICT,
488 and the web-API server recognizes the rw_uri as a write cap, then it will
489 reset the ro_uri to the corresponding read cap and discard the original
490 contents of ro_uri (in order to ensure that the two caps correspond to the
491 same object and that the ro_uri is in fact read-only). However this may not
492 happen for caps in a format unknown to the web-API server. Therefore, when
493 writing a directory the web-API client should ensure that the contents
494 of "rw_uri" and "ro_uri" for a given PROPDICT are a consistent
495 (write cap, read cap) pair if possible. If the web-API client only has
496 one cap and does not know whether it is a write cap or read cap, then
497 it is acceptable to set "rw_uri" to that cap and omit "ro_uri". The
498 client must not put a write cap into a "ro_uri" field.
500 The metadata may have a "no-write" field. If this is set to true in the
501 metadata of a link, it will not be possible to open that link for writing
502 via the SFTP frontend; see `<FTP-and-SFTP.rst>`_ for details.
503 Also, if the "no-write" field is set to true in the metadata of a link to
504 a mutable child, it will cause the link to be diminished to read-only.
506 Note that the web-API-using client application must not provide the
507 "Content-Type: multipart/form-data" header that usually accompanies HTML
508 form submissions, since the body is not formatted this way. Doing so will
509 cause a server error as the lower-level code misparses the request body.
511 Child file names should each be expressed as a Unicode string, then used as
512 keys of the dictionary. The dictionary should then be converted into JSON,
513 and the resulting string encoded into UTF-8. This UTF-8 bytestring should
514 then be used as the POST body.
516 ``POST /uri?t=mkdir-immutable``
518 Like t=mkdir-with-children above, but the new directory will be
519 deep-immutable. This means that the directory itself is immutable, and that
520 it can only contain objects that are treated as being deep-immutable, like
521 immutable files, literal files, and deep-immutable directories.
523 For forward-compatibility, a deep-immutable directory can also contain caps
524 in a format that is unknown to the web-API server. When such caps are retrieved
525 from a deep-immutable directory in a "ro_uri" field, they will be prefixed
526 with the string "imm.", indicating that they must not be decoded without
527 checking that they are immutable. The "imm." prefix must not be stripped
528 off without performing this check. (Future versions of the web-API server
529 will perform it where necessary.)
531 The cap for each child may be given either in the "rw_uri" or "ro_uri"
532 field of the PROPDICT (not both). If a cap is given in the "rw_uri" field,
533 then the web-API server will check that it is an immutable read-cap of a
534 *known* format, and give an error if it is not. If a cap is given in the
535 "ro_uri" field, then the web-API server will still check whether known
536 caps are immutable, but for unknown caps it will simply assume that the
537 cap can be stored, as described above. Note that an attacker would be
538 able to store any cap in an immutable directory, so this check when
539 creating the directory is only to help non-malicious clients to avoid
540 accidentally giving away more authority than intended.
542 A non-empty request body is mandatory, since after the directory is created,
543 it will not be possible to add more children to it.
545 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
547 ``PUT /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir``
549 Create new directories as necessary to make sure that the named target
550 ($DIRCAP/SUBDIRS../SUBDIR) is a directory. This will create additional
551 intermediate mutable directories as necessary. If the named target directory
552 already exists, this will make no changes to it.
554 If the final directory is created, it will be empty.
556 This accepts a format= argument in the query string, which controls the
557 format of the named target directory, if it does not already exist. format=
558 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
559 format= only controls the format of the named target directory;
560 intermediate directories, if created, are created based on the default
561 mutable type, as configured on the Tahoe-LAFS server responding to the
564 This operation will return an error if a blocking file is present at any of
565 the parent names, preventing the server from creating the necessary parent
566 directory; or if it would require changing an immutable directory.
568 The write-cap of the new directory will be returned as the HTTP response
571 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-with-children``
573 Like /uri?t=mkdir-with-children, but the final directory is created as a
574 child of an existing mutable directory. This will create additional
575 intermediate mutable directories as necessary. If the final directory is
576 created, it will be populated with initial children from the POST request
577 body, as described above.
579 This accepts a format= argument in the query string, which controls the
580 format of the target directory, if the target directory is created as part
581 of the operation. format= is interpreted in the same way as in the POST/
582 uri?t=mkdir-with-children operation. Note that format= only controls the
583 format of the named target directory; intermediate directories, if created,
584 are created using the default mutable type setting, as configured on the
585 Tahoe-LAFS server responding to the request.
587 This operation will return an error if a blocking file is present at any of
588 the parent names, preventing the server from creating the necessary parent
589 directory; or if it would require changing an immutable directory; or if
590 the immediate parent directory already has a a child named SUBDIR.
592 ``POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-immutable``
594 Like /uri?t=mkdir-immutable, but the final directory is created as a child
595 of an existing mutable directory. The final directory will be deep-immutable,
596 and will be populated with the children specified as a JSON dictionary in
597 the POST request body.
599 In Tahoe 1.6 this operation creates intermediate mutable directories if
600 necessary, but that behaviour should not be relied on; see ticket #920.
602 This operation will return an error if the parent directory is immutable,
603 or already has a child named SUBDIR.
605 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME``
607 Create a new empty mutable directory and attach it to the given existing
608 directory. This will create additional intermediate directories as necessary.
610 This accepts a format= argument in the query string, which controls the
611 format of the named target directory, if it does not already exist. format=
612 is interpreted in the same way as in the POST /uri?t=mkdir form. Note that
613 format= only controls the format of the named target directory;
614 intermediate directories, if created, are created based on the default
615 mutable type, as configured on the Tahoe-LAFS server responding to the
618 This operation will return an error if a blocking file is present at any of
619 the parent names, preventing the server from creating the necessary parent
620 directory, or if it would require changing any immutable directory.
622 The URL of this operation points to the parent of the bottommost new directory,
623 whereas the /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir operation above has a URL
624 that points directly to the bottommost new directory.
626 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME``
628 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME, but the new directory will
629 be populated with initial children via the POST request body. This command
630 will create additional intermediate mutable directories as necessary.
632 This accepts a format= argument in the query string, which controls the
633 format of the target directory, if the target directory is created as part
634 of the operation. format= is interpreted in the same way as in the POST/
635 uri?t=mkdir-with-children operation. Note that format= only controls the
636 format of the named target directory; intermediate directories, if created,
637 are created using the default mutable type setting, as configured on the
638 Tahoe-LAFS server responding to the request.
640 This operation will return an error if a blocking file is present at any of
641 the parent names, preventing the server from creating the necessary parent
642 directory; or if it would require changing an immutable directory; or if
643 the immediate parent directory already has a a child named NAME.
645 Note that the name= argument must be passed as a queryarg, because the POST
646 request body is used for the initial children JSON.
648 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-immutable&name=NAME``
650 Like /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME, but the
651 final directory will be deep-immutable. The children are specified as a
652 JSON dictionary in the POST request body. Again, the name= argument must be
653 passed as a queryarg.
655 In Tahoe 1.6 this operation creates intermediate mutable directories if
656 necessary, but that behaviour should not be relied on; see ticket #920.
658 This operation will return an error if the parent directory is immutable,
659 or already has a child named NAME.
662 Getting Information About A File Or Directory (as JSON)
663 -------------------------------------------------------
665 ``GET /uri/$FILECAP?t=json``
667 ``GET /uri/$DIRCAP?t=json``
669 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json``
671 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json``
673 This returns a machine-parseable JSON-encoded description of the given
674 object. The JSON always contains a list, and the first element of the list is
675 always a flag that indicates whether the referenced object is a file or a
676 directory. If it is a capability to a file, then the information includes
677 file size and URI, like this::
679 GET /uri/$FILECAP?t=json :
683 "verify_uri": verify_uri,
689 If it is a capability to a directory followed by a path from that directory
690 to a file, then the information also includes metadata from the link to the
691 file in the parent directory, like this::
693 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json
697 "verify_uri": verify_uri,
702 "ctime": 1202777696.7564139,
703 "mtime": 1202777696.7564139,
705 "linkcrtime": 1202777696.7564139,
706 "linkmotime": 1202777696.7564139
709 If it is a directory, then it includes information about the children of
710 this directory, as a mapping from child name to a set of data about the
711 child (the same data that would appear in a corresponding GET?t=json of the
712 child itself). The child entries also include metadata about each child,
713 including link-creation- and link-change- timestamps. The output looks like
716 GET /uri/$DIRCAP?t=json :
717 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json :
720 "rw_uri": read_write_uri,
721 "ro_uri": read_only_uri,
722 "verify_uri": verify_uri,
726 "foo.txt": [ "filenode",
731 "ctime": 1202777696.7564139,
732 "mtime": 1202777696.7564139,
734 "linkcrtime": 1202777696.7564139,
735 "linkmotime": 1202777696.7564139
737 "subdir": [ "dirnode",
742 "ctime": 1202778102.7589991,
743 "mtime": 1202778111.2160511,
745 "linkcrtime": 1202777696.7564139,
746 "linkmotime": 1202777696.7564139
750 In the above example, note how 'children' is a dictionary in which the keys
751 are child names and the values depend upon whether the child is a file or a
752 directory. The value is mostly the same as the JSON representation of the
753 child object (except that directories do not recurse -- the "children"
754 entry of the child is omitted, and the directory view includes the metadata
755 that is stored on the directory edge).
757 The rw_uri field will be present in the information about a directory
758 if and only if you have read-write access to that directory. The verify_uri
759 field will be present if and only if the object has a verify-cap
760 (non-distributed LIT files do not have verify-caps).
762 If the cap is of an unknown format, then the file size and verify_uri will
765 GET /uri/$UNKNOWNCAP?t=json :
768 "ro_uri": unknown_read_uri
771 GET /uri/$DIRCAP/[SUBDIRS../]UNKNOWNCHILDNAME?t=json :
774 "rw_uri": unknown_write_uri,
775 "ro_uri": unknown_read_uri,
778 "ctime": 1202777696.7564139,
779 "mtime": 1202777696.7564139,
781 "linkcrtime": 1202777696.7564139,
782 "linkmotime": 1202777696.7564139
785 As in the case of file nodes, the metadata will only be present when the
786 capability is to a directory followed by a path. The "mutable" field is also
787 not always present; when it is absent, the mutability of the object is not
793 The value of the 'tahoe':'linkmotime' key is updated whenever a link to a
794 child is set. The value of the 'tahoe':'linkcrtime' key is updated whenever
795 a link to a child is created -- i.e. when there was not previously a link
798 Note however, that if the edge in the Tahoe filesystem points to a mutable
799 file and the contents of that mutable file is changed, then the
800 'tahoe':'linkmotime' value on that edge will *not* be updated, since the
801 edge itself wasn't updated -- only the mutable file was.
803 The timestamps are represented as a number of seconds since the UNIX epoch
804 (1970-01-01 00:00:00 UTC), with leap seconds not being counted in the long
807 In Tahoe earlier than v1.4.0, 'mtime' and 'ctime' keys were populated
808 instead of the 'tahoe':'linkmotime' and 'tahoe':'linkcrtime' keys. Starting
809 in Tahoe v1.4.0, the 'linkmotime'/'linkcrtime' keys in the 'tahoe' sub-dict
810 are populated. However, prior to Tahoe v1.7beta, a bug caused the 'tahoe'
811 sub-dict to be deleted by web-API requests in which new metadata is
812 specified, and not to be added to existing child links that lack it.
814 From Tahoe v1.7.0 onward, the 'mtime' and 'ctime' fields are no longer
815 populated or updated (see ticket #924), except by "tahoe backup" as
816 explained below. For backward compatibility, when an existing link is
817 updated and 'tahoe':'linkcrtime' is not present in the previous metadata
818 but 'ctime' is, the old value of 'ctime' is used as the new value of
819 'tahoe':'linkcrtime'.
821 The reason we added the new fields in Tahoe v1.4.0 is that there is a
822 "set_children" API (described below) which you can use to overwrite the
823 values of the 'mtime'/'ctime' pair, and this API is used by the
824 "tahoe backup" command (in Tahoe v1.3.0 and later) to set the 'mtime' and
825 'ctime' values when backing up files from a local filesystem into the
826 Tahoe filesystem. As of Tahoe v1.4.0, the set_children API cannot be used
827 to set anything under the 'tahoe' key of the metadata dict -- if you
828 include 'tahoe' keys in your 'metadata' arguments then it will silently
831 Therefore, if the 'tahoe' sub-dict is present, you can rely on the
832 'linkcrtime' and 'linkmotime' values therein to have the semantics described
833 above. (This is assuming that only official Tahoe clients have been used to
834 write those links, and that their system clocks were set to what you expected
835 -- there is nothing preventing someone from editing their Tahoe client or
836 writing their own Tahoe client which would overwrite those values however
837 they like, and there is nothing to constrain their system clock from taking
840 When an edge is created or updated by "tahoe backup", the 'mtime' and
841 'ctime' keys on that edge are set as follows:
843 * 'mtime' is set to the timestamp read from the local filesystem for the
844 "mtime" of the local file in question, which means the last time the
845 contents of that file were changed.
847 * On Windows, 'ctime' is set to the creation timestamp for the file
848 read from the local filesystem. On other platforms, 'ctime' is set to
849 the UNIX "ctime" of the local file, which means the last time that
850 either the contents or the metadata of the local file was changed.
852 There are several ways that the 'ctime' field could be confusing:
854 1. You might be confused about whether it reflects the time of the creation
855 of a link in the Tahoe filesystem (by a version of Tahoe < v1.7.0) or a
856 timestamp copied in by "tahoe backup" from a local filesystem.
858 2. You might be confused about whether it is a copy of the file creation
859 time (if "tahoe backup" was run on a Windows system) or of the last
860 contents-or-metadata change (if "tahoe backup" was run on a different
863 3. You might be confused by the fact that changing the contents of a
864 mutable file in Tahoe doesn't have any effect on any links pointing at
865 that file in any directories, although "tahoe backup" sets the link
866 'ctime'/'mtime' to reflect timestamps about the local file corresponding
867 to the Tahoe file to which the link points.
869 4. Also, quite apart from Tahoe, you might be confused about the meaning
870 of the "ctime" in UNIX local filesystems, which people sometimes think
871 means file creation time, but which actually means, in UNIX local
872 filesystems, the most recent time that the file contents or the file
873 metadata (such as owner, permission bits, extended attributes, etc.)
874 has changed. Note that although "ctime" does not mean file creation time
875 in UNIX, links created by a version of Tahoe prior to v1.7.0, and never
876 written by "tahoe backup", will have 'ctime' set to the link creation
880 Attaching an Existing File or Directory by its read- or write-cap
881 -----------------------------------------------------------------
883 ``PUT /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
885 This attaches a child object (either a file or directory) to a specified
886 location in the virtual filesystem. The child object is referenced by its
887 read- or write- cap, as provided in the HTTP request body. This will create
888 intermediate directories as necessary.
890 This is similar to a UNIX hardlink: by referencing a previously-uploaded file
891 (or previously-created directory) instead of uploading/creating a new one,
892 you can create two references to the same object.
894 The read- or write- cap of the child is provided in the body of the HTTP
895 request, and this same cap is returned in the response body.
897 The default behavior is to overwrite any existing object at the same
898 location. To prevent this (and make the operation return an error instead
899 of overwriting), add a "replace=false" argument, as "?t=uri&replace=false".
900 With replace=false, this operation will return an HTTP 409 "Conflict" error
901 if there is already an object at the given location, rather than
902 overwriting the existing object. To allow the operation to overwrite a
903 file, but return an error when trying to overwrite a directory, use
904 "replace=only-files" (this behavior is closer to the traditional UNIX "mv"
905 command). Note that "true", "t", and "1" are all synonyms for "True", and
906 "false", "f", and "0" are synonyms for "False", and the parameter is
909 Note that this operation does not take its child cap in the form of
910 separate "rw_uri" and "ro_uri" fields. Therefore, it cannot accept a
911 child cap in a format unknown to the web-API server, unless its URI
912 starts with "ro." or "imm.". This restriction is necessary because the
913 server is not able to attenuate an unknown write cap to a read cap.
914 Unknown URIs starting with "ro." or "imm.", on the other hand, are
915 assumed to represent read caps. The client should not prefix a write
916 cap with "ro." or "imm." and pass it to this operation, since that
917 would result in granting the cap's write authority to holders of the
921 Adding Multiple Files or Directories to a Parent Directory at Once
922 ------------------------------------------------------------------
924 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set_children``
926 ``POST /uri/$DIRCAP/[SUBDIRS..]?t=set-children`` (Tahoe >= v1.6)
928 This command adds multiple children to a directory in a single operation.
929 It reads the request body and interprets it as a JSON-encoded description
930 of the child names and read/write-caps that should be added.
932 The body should be a JSON-encoded dictionary, in the same format as the
933 "children" value returned by the "GET /uri/$DIRCAP?t=json" operation
934 described above. In this format, each key is a child names, and the
935 corresponding value is a tuple of (type, childinfo). "type" is ignored, and
936 "childinfo" is a dictionary that contains "rw_uri", "ro_uri", and
937 "metadata" keys. You can take the output of "GET /uri/$DIRCAP1?t=json" and
938 use it as the input to "POST /uri/$DIRCAP2?t=set_children" to make DIR2
939 look very much like DIR1 (except for any existing children of DIR2 that
940 were not overwritten, and any existing "tahoe" metadata keys as described
943 When the set_children request contains a child name that already exists in
944 the target directory, this command defaults to overwriting that child with
945 the new value (both child cap and metadata, but if the JSON data does not
946 contain a "metadata" key, the old child's metadata is preserved). The
947 command takes a boolean "overwrite=" query argument to control this
948 behavior. If you use "?t=set_children&overwrite=false", then an attempt to
949 replace an existing child will instead cause an error.
951 Any "tahoe" key in the new child's "metadata" value is ignored. Any
952 existing "tahoe" metadata is preserved. The metadata["tahoe"] value is
953 reserved for metadata generated by the tahoe node itself. The only two keys
954 currently placed here are "linkcrtime" and "linkmotime". For details, see
955 the section above entitled "Get Information About A File Or Directory (as
956 JSON)", in the "About the metadata" subsection.
958 Note that this command was introduced with the name "set_children", which
959 uses an underscore rather than a hyphen as other multi-word command names
960 do. The variant with a hyphen is now accepted, but clients that desire
961 backward compatibility should continue to use "set_children".
964 Unlinking a File or Directory
965 -----------------------------
967 ``DELETE /uri/$DIRCAP/[SUBDIRS../]CHILDNAME``
969 This removes the given name from its parent directory. CHILDNAME is the
970 name to be removed, and $DIRCAP/SUBDIRS.. indicates the directory that will
973 Note that this does not actually delete the file or directory that the name
974 points to from the tahoe grid -- it only unlinks the named reference from
975 this directory. If there are other names in this directory or in other
976 directories that point to the resource, then it will remain accessible
977 through those paths. Even if all names pointing to this object are removed
978 from their parent directories, then someone with possession of its read-cap
979 can continue to access the object through that cap.
981 The object will only become completely unreachable once 1: there are no
982 reachable directories that reference it, and 2: nobody is holding a read-
983 or write- cap to the object. (This behavior is very similar to the way
984 hardlinks and anonymous files work in traditional UNIX filesystems).
986 This operation will not modify more than a single directory. Intermediate
987 directories which were implicitly created by PUT or POST methods will *not*
988 be automatically removed by DELETE.
990 This method returns the file- or directory- cap of the object that was just
994 Browser Operations: Human-oriented interfaces
995 =============================================
997 This section describes the HTTP operations that provide support for humans
998 running a web browser. Most of these operations use HTML forms that use POST
999 to drive the Tahoe node. This section is intended for HTML authors who want
1000 to write web pages that contain forms and buttons which manipulate the Tahoe
1003 Note that for all POST operations, the arguments listed can be provided
1004 either as URL query arguments or as form body fields. URL query arguments are
1005 separated from the main URL by "?", and from each other by "&". For example,
1006 "POST /uri/$DIRCAP?t=upload&mutable=true". Form body fields are usually
1007 specified by using <input type="hidden"> elements. For clarity, the
1008 descriptions below display the most significant arguments as URL query args.
1011 Viewing A Directory (as HTML)
1012 -----------------------------
1014 ``GET /uri/$DIRCAP/[SUBDIRS../]``
1016 This returns an HTML page, intended to be displayed to a human by a web
1017 browser, which contains HREF links to all files and directories reachable
1018 from this directory. These HREF links do not have a t= argument, meaning
1019 that a human who follows them will get pages also meant for a human. It also
1020 contains forms to upload new files, and to unlink files and directories
1021 from their parent directory. Those forms use POST methods to do their job.
1024 Viewing/Downloading a File
1025 --------------------------
1027 ``GET /uri/$FILECAP``
1029 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME``
1031 This will retrieve the contents of the given file. The HTTP response body
1032 will contain the sequence of bytes that make up the file.
1034 If you want the HTTP response to include a useful Content-Type header,
1035 either use the second form (which starts with a $DIRCAP), or add a
1036 "filename=foo" query argument, like "GET /uri/$FILECAP?filename=foo.jpg".
1037 The bare "GET /uri/$FILECAP" does not give the Tahoe node enough information
1038 to determine a Content-Type (since Tahoe immutable files are merely
1039 sequences of bytes, not typed+named file objects).
1041 If the URL has both filename= and "save=true" in the query arguments, then
1042 the server to add a "Content-Disposition: attachment" header, along with a
1043 filename= parameter. When a user clicks on such a link, most browsers will
1044 offer to let the user save the file instead of displaying it inline (indeed,
1045 most browsers will refuse to display it inline). "true", "t", "1", and other
1046 case-insensitive equivalents are all treated the same.
1048 Character-set handling in URLs and HTTP headers is a dubious art [1]_. For
1049 maximum compatibility, Tahoe simply copies the bytes from the filename=
1050 argument into the Content-Disposition header's filename= parameter, without
1051 trying to interpret them in any particular way.
1054 ``GET /named/$FILECAP/FILENAME``
1056 This is an alternate download form which makes it easier to get the correct
1057 filename. The Tahoe server will provide the contents of the given file, with
1058 a Content-Type header derived from the given filename. This form is used to
1059 get browsers to use the "Save Link As" feature correctly, and also helps
1060 command-line tools like "wget" and "curl" use the right filename. Note that
1061 this form can *only* be used with file caps; it is an error to use a
1062 directory cap after the /named/ prefix.
1065 Getting Information About A File Or Directory (as HTML)
1066 -------------------------------------------------------
1068 ``GET /uri/$FILECAP?t=info``
1070 ``GET /uri/$DIRCAP/?t=info``
1072 ``GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR/?t=info``
1074 ``GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=info``
1076 This returns a human-oriented HTML page with more detail about the selected
1077 file or directory object. This page contains the following items:
1081 * JSON representation
1082 * raw contents (text/plain)
1083 * access caps (URIs): verify-cap, read-cap, write-cap (for mutable objects)
1084 * check/verify/repair form
1085 * deep-check/deep-size/deep-stats/manifest (for directories)
1086 * replace-contents form (for mutable files)
1089 Creating a Directory
1090 --------------------
1092 ``POST /uri?t=mkdir``
1094 This creates a new empty directory, but does not attach it to the virtual
1097 If a "redirect_to_result=true" argument is provided, then the HTTP response
1098 will cause the web browser to be redirected to a /uri/$DIRCAP page that
1099 gives access to the newly-created directory. If you bookmark this page,
1100 you'll be able to get back to the directory again in the future. This is the
1101 recommended way to start working with a Tahoe server: create a new unlinked
1102 directory (using redirect_to_result=true), then bookmark the resulting
1103 /uri/$DIRCAP page. There is a "create directory" button on the Welcome page
1104 to invoke this action.
1106 This accepts a format= argument in the query string. Refer to the
1107 documentation of the PUT /uri?t=mkdir operation in `Creating A
1108 New Directory`_ for information on the behavior of the format= argument.
1110 If "redirect_to_result=true" is not provided (or is given a value of
1111 "false"), then the HTTP response body will simply be the write-cap of the
1114 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME``
1116 This creates a new empty directory as a child of the designated SUBDIR. This
1117 will create additional intermediate directories as necessary.
1119 This accepts a format= argument in the query string. Refer to the
1120 documentation of POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME in
1121 `Creating A New Directory`_ for information on the behavior of the format=
1124 If a "when_done=URL" argument is provided, the HTTP response will cause the
1125 web browser to redirect to the given URL. This provides a convenient way to
1126 return the browser to the directory that was just modified. Without a
1127 when_done= argument, the HTTP response will simply contain the write-cap of
1128 the directory that was just created.
1134 ``POST /uri?t=upload``
1136 This uploads a file, and produces a file-cap for the contents, but does not
1137 attach the file into the filesystem. No directories will be modified by
1140 The file must be provided as the "file" field of an HTML encoded form body,
1141 produced in response to an HTML form like this::
1143 <form action="/uri" method="POST" enctype="multipart/form-data">
1144 <input type="hidden" name="t" value="upload" />
1145 <input type="file" name="file" />
1146 <input type="submit" value="Upload Unlinked" />
1149 If a "when_done=URL" argument is provided, the response body will cause the
1150 browser to redirect to the given URL. If the when_done= URL has the string
1151 "%(uri)s" in it, that string will be replaced by a URL-escaped form of the
1152 newly created file-cap. (Note that without this substitution, there is no
1153 way to access the file that was just uploaded).
1155 The default (in the absence of when_done=) is to return an HTML page that
1156 describes the results of the upload. This page will contain information
1157 about which storage servers were used for the upload, how long each
1158 operation took, etc.
1160 This accepts format= and mutable=true query string arguments. Refer to
1161 `Writing/Uploading A File`_ for information on the behavior of format= and
1164 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=upload``
1166 This uploads a file, and attaches it as a new child of the given directory,
1167 which must be mutable. The file must be provided as the "file" field of an
1168 HTML-encoded form body, produced in response to an HTML form like this::
1170 <form action="." method="POST" enctype="multipart/form-data">
1171 <input type="hidden" name="t" value="upload" />
1172 <input type="file" name="file" />
1173 <input type="submit" value="Upload" />
1176 A "name=" argument can be provided to specify the new child's name,
1177 otherwise it will be taken from the "filename" field of the upload form
1178 (most web browsers will copy the last component of the original file's
1179 pathname into this field). To avoid confusion, name= is not allowed to
1182 If there is already a child with that name, and it is a mutable file, then
1183 its contents are replaced with the data being uploaded. If it is not a
1184 mutable file, the default behavior is to remove the existing child before
1185 creating a new one. To prevent this (and make the operation return an error
1186 instead of overwriting the old child), add a "replace=false" argument, as
1187 "?t=upload&replace=false". With replace=false, this operation will return an
1188 HTTP 409 "Conflict" error if there is already an object at the given
1189 location, rather than overwriting the existing object. Note that "true",
1190 "t", and "1" are all synonyms for "True", and "false", "f", and "0" are
1191 synonyms for "False". the parameter is case-insensitive.
1193 This will create additional intermediate directories as necessary, although
1194 since it is expected to be triggered by a form that was retrieved by "GET
1195 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1198 This accepts format= and mutable=true query string arguments. Refer to
1199 `Writing/Uploading A File`_ for information on the behavior of format= and
1202 If a "when_done=URL" argument is provided, the HTTP response will cause the
1203 web browser to redirect to the given URL. This provides a convenient way to
1204 return the browser to the directory that was just modified. Without a
1205 when_done= argument, the HTTP response will simply contain the file-cap of
1206 the file that was just uploaded (a write-cap for mutable files, or a
1207 read-cap for immutable files).
1209 ``POST /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=upload``
1211 This also uploads a file and attaches it as a new child of the given
1212 directory, which must be mutable. It is a slight variant of the previous
1213 operation, as the URL refers to the target file rather than the parent
1214 directory. It is otherwise identical: this accepts mutable= and when_done=
1217 ``POST /uri/$FILECAP?t=upload``
1219 This modifies the contents of an existing mutable file in-place. An error is
1220 signalled if $FILECAP does not refer to a mutable file. It behaves just like
1221 the "PUT /uri/$FILECAP" form, but uses a POST for the benefit of HTML forms
1225 Attaching An Existing File Or Directory (by URI)
1226 ------------------------------------------------
1228 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=uri&name=CHILDNAME&uri=CHILDCAP``
1230 This attaches a given read- or write- cap "CHILDCAP" to the designated
1231 directory, with a specified child name. This behaves much like the PUT t=uri
1232 operation, and is a lot like a UNIX hardlink. It is subject to the same
1233 restrictions as that operation on the use of cap formats unknown to the
1236 This will create additional intermediate directories as necessary, although
1237 since it is expected to be triggered by a form that was retrieved by "GET
1238 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
1241 This accepts the same replace= argument as POST t=upload.
1247 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=delete&name=CHILDNAME``
1249 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=unlink&name=CHILDNAME``
1251 This instructs the node to remove a child object (file or subdirectory) from
1252 the given directory, which must be mutable. Note that the entire subtree is
1253 unlinked from the parent. Unlike deleting a subdirectory in a UNIX local
1254 filesystem, the subtree need not be empty; if it isn't, then other references
1255 into the subtree will see that the child subdirectories are not modified by
1256 this operation. Only the link from the given directory to its child is severed.
1258 In Tahoe-LAFS v1.9.0 and later, t=unlink can be used as a synonym for t=delete.
1259 If interoperability with older web-API servers is required, t=delete should
1266 ``POST /uri/$DIRCAP/[SUBDIRS../]?t=rename&from_name=OLD&to_name=NEW``
1268 This instructs the node to rename a child of the given directory, which must
1269 be mutable. This has a similar effect to removing the child, then adding the
1270 same child-cap under the new name, except that it preserves metadata. This
1271 operation cannot move the child to a different directory.
1273 This operation will replace any existing child of the new name, making it
1274 behave like the UNIX "``mv -f``" command.
1279 ``GET /uri?uri=$CAP``
1281 This causes a redirect to /uri/$CAP, and retains any additional query
1282 arguments (like filename= or save=). This is for the convenience of web
1283 forms which allow the user to paste in a read- or write- cap (obtained
1284 through some out-of-band channel, like IM or email).
1286 Note that this form merely redirects to the specific file or directory
1287 indicated by the $CAP: unlike the GET /uri/$DIRCAP form, you cannot
1288 traverse to children by appending additional path segments to the URL.
1290 ``GET /uri/$DIRCAP/[SUBDIRS../]?t=rename-form&name=$CHILDNAME``
1292 This provides a useful facility to browser-based user interfaces. It
1293 returns a page containing a form targetting the "POST $DIRCAP t=rename"
1294 functionality described above, with the provided $CHILDNAME present in the
1295 'from_name' field of that form. I.e. this presents a form offering to
1296 rename $CHILDNAME, requesting the new name, and submitting POST rename.
1298 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri``
1300 This returns the file- or directory- cap for the specified object.
1302 ``GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=readonly-uri``
1304 This returns a read-only file- or directory- cap for the specified object.
1305 If the object is an immutable file, this will return the same value as
1309 Debugging and Testing Features
1310 ------------------------------
1312 These URLs are less-likely to be helpful to the casual Tahoe user, and are
1313 mainly intended for developers.
1315 ``POST $URL?t=check``
1317 This triggers the FileChecker to determine the current "health" of the
1318 given file or directory, by counting how many shares are available. The
1319 page that is returned will display the results. This can be used as a "show
1320 me detailed information about this file" page.
1322 If a verify=true argument is provided, the node will perform a more
1323 intensive check, downloading and verifying every single bit of every share.
1325 If an add-lease=true argument is provided, the node will also add (or
1326 renew) a lease to every share it encounters. Each lease will keep the share
1327 alive for a certain period of time (one month by default). Once the last
1328 lease expires or is explicitly cancelled, the storage server is allowed to
1331 If an output=JSON argument is provided, the response will be
1332 machine-readable JSON instead of human-oriented HTML. The data is a
1333 dictionary with the following keys::
1335 storage-index: a base32-encoded string with the objects's storage index,
1336 or an empty string for LIT files
1337 summary: a string, with a one-line summary of the stats of the file
1338 results: a dictionary that describes the state of the file. For LIT files,
1339 this dictionary has only the 'healthy' key, which will always be
1340 True. For distributed files, this dictionary has the following
1342 count-shares-good: the number of good shares that were found
1343 count-shares-needed: 'k', the number of shares required for recovery
1344 count-shares-expected: 'N', the number of total shares generated
1345 count-good-share-hosts: this was intended to be the number of distinct
1346 storage servers with good shares. It is currently
1347 (as of Tahoe-LAFS v1.8.0) computed incorrectly;
1349 count-wrong-shares: for mutable files, the number of shares for
1350 versions other than the 'best' one (highest
1351 sequence number, highest roothash). These are
1353 count-recoverable-versions: for mutable files, the number of
1354 recoverable versions of the file. For
1355 a healthy file, this will equal 1.
1356 count-unrecoverable-versions: for mutable files, the number of
1357 unrecoverable versions of the file.
1358 For a healthy file, this will be 0.
1359 count-corrupt-shares: the number of shares with integrity failures
1360 list-corrupt-shares: a list of "share locators", one for each share
1361 that was found to be corrupt. Each share locator
1362 is a list of (serverid, storage_index, sharenum).
1363 needs-rebalancing: (bool) True if there are multiple shares on a single
1364 storage server, indicating a reduction in reliability
1365 that could be resolved by moving shares to new
1367 servers-responding: list of base32-encoded storage server identifiers,
1368 one for each server which responded to the share
1370 healthy: (bool) True if the file is completely healthy, False otherwise.
1371 Healthy files have at least N good shares. Overlapping shares
1372 do not currently cause a file to be marked unhealthy. If there
1373 are at least N good shares, then corrupt shares do not cause the
1374 file to be marked unhealthy, although the corrupt shares will be
1375 listed in the results (list-corrupt-shares) and should be manually
1376 removed to wasting time in subsequent downloads (as the
1377 downloader rediscovers the corruption and uses alternate shares).
1378 Future compatibility: the meaning of this field may change to
1379 reflect whether the servers-of-happiness criterion is met
1381 sharemap: dict mapping share identifier to list of serverids
1382 (base32-encoded strings). This indicates which servers are
1383 holding which shares. For immutable files, the shareid is
1384 an integer (the share number, from 0 to N-1). For
1385 immutable files, it is a string of the form
1386 'seq%d-%s-sh%d', containing the sequence number, the
1387 roothash, and the share number.
1389 ``POST $URL?t=start-deep-check`` (must add &ophandle=XYZ)
1391 This initiates a recursive walk of all files and directories reachable from
1392 the target, performing a check on each one just like t=check. The result
1393 page will contain a summary of the results, including details on any
1394 file/directory that was not fully healthy.
1396 t=start-deep-check can only be invoked on a directory. An error (400
1397 BAD_REQUEST) will be signalled if it is invoked on a file. The recursive
1398 walker will deal with loops safely.
1400 This accepts the same verify= and add-lease= arguments as t=check.
1402 Since this operation can take a long time (perhaps a second per object),
1403 the ophandle= argument is required (see "Slow Operations, Progress, and
1404 Cancelling" above). The response to this POST will be a redirect to the
1405 corresponding /operations/$HANDLE page (with output=HTML or output=JSON to
1406 match the output= argument given to the POST). The deep-check operation
1407 will continue to run in the background, and the /operations page should be
1408 used to find out when the operation is done.
1410 Detailed check results for non-healthy files and directories will be
1411 available under /operations/$HANDLE/$STORAGEINDEX, and the HTML status will
1412 contain links to these detailed results.
1414 The HTML /operations/$HANDLE page for incomplete operations will contain a
1415 meta-refresh tag, set to 60 seconds, so that a browser which uses
1416 deep-check will automatically poll until the operation has completed.
1418 The JSON page (/options/$HANDLE?output=JSON) will contain a
1419 machine-readable JSON dictionary with the following keys::
1421 finished: a boolean, True if the operation is complete, else False. Some
1422 of the remaining keys may not be present until the operation
1424 root-storage-index: a base32-encoded string with the storage index of the
1425 starting point of the deep-check operation
1426 count-objects-checked: count of how many objects were checked. Note that
1427 non-distributed objects (i.e. small immutable LIT
1428 files) are not checked, since for these objects,
1429 the data is contained entirely in the URI.
1430 count-objects-healthy: how many of those objects were completely healthy
1431 count-objects-unhealthy: how many were damaged in some way
1432 count-corrupt-shares: how many shares were found to have corruption,
1433 summed over all objects examined
1434 list-corrupt-shares: a list of "share identifiers", one for each share
1435 that was found to be corrupt. Each share identifier
1436 is a list of (serverid, storage_index, sharenum).
1437 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1438 each file that was not fully healthy. 'pathname' is
1439 a list of strings (which can be joined by "/"
1440 characters to turn it into a single string),
1441 relative to the directory on which deep-check was
1442 invoked. The 'check-results' field is the same as
1443 that returned by t=check&output=JSON, described
1445 stats: a dictionary with the same keys as the t=start-deep-stats command
1448 ``POST $URL?t=stream-deep-check``
1450 This initiates a recursive walk of all files and directories reachable from
1451 the target, performing a check on each one just like t=check. For each
1452 unique object (duplicates are skipped), a single line of JSON is emitted to
1453 the HTTP response channel (or an error indication, see below). When the walk
1454 is complete, a final line of JSON is emitted which contains the accumulated
1455 file-size/count "deep-stats" data.
1457 This command takes the same arguments as t=start-deep-check.
1459 A CLI tool can split the response stream on newlines into "response units",
1460 and parse each response unit as JSON. Each such parsed unit will be a
1461 dictionary, and will contain at least the "type" key: a string, one of
1462 "file", "directory", or "stats".
1464 For all units that have a type of "file" or "directory", the dictionary will
1465 contain the following keys::
1467 "path": a list of strings, with the path that is traversed to reach the
1469 "cap": a write-cap URI for the file or directory, if available, else a
1471 "verifycap": a verify-cap URI for the file or directory
1472 "repaircap": an URI for the weakest cap that can still be used to repair
1474 "storage-index": a base32 storage index for the object
1475 "check-results": a copy of the dictionary which would be returned by
1476 t=check&output=json, with three top-level keys:
1477 "storage-index", "summary", and "results", and a variety
1478 of counts and sharemaps in the "results" value.
1480 Note that non-distributed files (i.e. LIT files) will have values of None
1481 for verifycap, repaircap, and storage-index, since these files can neither
1482 be verified nor repaired, and are not stored on the storage servers.
1483 Likewise the check-results dictionary will be limited: an empty string for
1484 storage-index, and a results dictionary with only the "healthy" key.
1486 The last unit in the stream will have a type of "stats", and will contain
1487 the keys described in the "start-deep-stats" operation, below.
1489 If any errors occur during the traversal (specifically if a directory is
1490 unrecoverable, such that further traversal is not possible), an error
1491 indication is written to the response body, instead of the usual line of
1492 JSON. This error indication line will begin with the string "ERROR:" (in all
1493 caps), and contain a summary of the error on the rest of the line. The
1494 remaining lines of the response body will be a python exception. The client
1495 application should look for the ERROR: and stop processing JSON as soon as
1496 it is seen. Note that neither a file being unrecoverable nor a directory
1497 merely being unhealthy will cause traversal to stop. The line just before
1498 the ERROR: will describe the directory that was untraversable, since the
1499 unit is emitted to the HTTP response body before the child is traversed.
1502 ``POST $URL?t=check&repair=true``
1504 This performs a health check of the given file or directory, and if the
1505 checker determines that the object is not healthy (some shares are missing
1506 or corrupted), it will perform a "repair". During repair, any missing
1507 shares will be regenerated and uploaded to new servers.
1509 This accepts the same verify=true and add-lease= arguments as t=check. When
1510 an output=JSON argument is provided, the machine-readable JSON response
1511 will contain the following keys::
1513 storage-index: a base32-encoded string with the objects's storage index,
1514 or an empty string for LIT files
1515 repair-attempted: (bool) True if repair was attempted
1516 repair-successful: (bool) True if repair was attempted and the file was
1517 fully healthy afterwards. False if no repair was
1518 attempted, or if a repair attempt failed.
1519 pre-repair-results: a dictionary that describes the state of the file
1520 before any repair was performed. This contains exactly
1521 the same keys as the 'results' value of the t=check
1522 response, described above.
1523 post-repair-results: a dictionary that describes the state of the file
1524 after any repair was performed. If no repair was
1525 performed, post-repair-results and pre-repair-results
1526 will be the same. This contains exactly the same keys
1527 as the 'results' value of the t=check response,
1530 ``POST $URL?t=start-deep-check&repair=true`` (must add &ophandle=XYZ)
1532 This triggers a recursive walk of all files and directories, performing a
1533 t=check&repair=true on each one.
1535 Like t=start-deep-check without the repair= argument, this can only be
1536 invoked on a directory. An error (400 BAD_REQUEST) will be signalled if it
1537 is invoked on a file. The recursive walker will deal with loops safely.
1539 This accepts the same verify= and add-lease= arguments as
1540 t=start-deep-check. It uses the same ophandle= mechanism as
1541 start-deep-check. When an output=JSON argument is provided, the response
1542 will contain the following keys::
1544 finished: (bool) True if the operation has completed, else False
1545 root-storage-index: a base32-encoded string with the storage index of the
1546 starting point of the deep-check operation
1547 count-objects-checked: count of how many objects were checked
1549 count-objects-healthy-pre-repair: how many of those objects were completely
1550 healthy, before any repair
1551 count-objects-unhealthy-pre-repair: how many were damaged in some way
1552 count-objects-healthy-post-repair: how many of those objects were completely
1553 healthy, after any repair
1554 count-objects-unhealthy-post-repair: how many were damaged in some way
1556 count-repairs-attempted: repairs were attempted on this many objects.
1557 count-repairs-successful: how many repairs resulted in healthy objects
1558 count-repairs-unsuccessful: how many repairs resulted did not results in
1559 completely healthy objects
1560 count-corrupt-shares-pre-repair: how many shares were found to have
1561 corruption, summed over all objects
1562 examined, before any repair
1563 count-corrupt-shares-post-repair: how many shares were found to have
1564 corruption, summed over all objects
1565 examined, after any repair
1566 list-corrupt-shares: a list of "share identifiers", one for each share
1567 that was found to be corrupt (before any repair).
1568 Each share identifier is a list of (serverid,
1569 storage_index, sharenum).
1570 list-remaining-corrupt-shares: like list-corrupt-shares, but mutable shares
1571 that were successfully repaired are not
1572 included. These are shares that need
1573 manual processing. Since immutable shares
1574 cannot be modified by clients, all corruption
1575 in immutable shares will be listed here.
1576 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1577 each file that was not fully healthy. 'pathname' is
1578 relative to the directory on which deep-check was
1579 invoked. The 'check-results' field is the same as
1580 that returned by t=check&repair=true&output=JSON,
1582 stats: a dictionary with the same keys as the t=start-deep-stats command
1585 ``POST $URL?t=stream-deep-check&repair=true``
1587 This triggers a recursive walk of all files and directories, performing a
1588 t=check&repair=true on each one. For each unique object (duplicates are
1589 skipped), a single line of JSON is emitted to the HTTP response channel (or
1590 an error indication). When the walk is complete, a final line of JSON is
1591 emitted which contains the accumulated file-size/count "deep-stats" data.
1593 This emits the same data as t=stream-deep-check (without the repair=true),
1594 except that the "check-results" field is replaced with a
1595 "check-and-repair-results" field, which contains the keys returned by
1596 t=check&repair=true&output=json (i.e. repair-attempted, repair-successful,
1597 pre-repair-results, and post-repair-results). The output does not contain
1598 the summary dictionary that is provied by t=start-deep-check&repair=true
1599 (the one with count-objects-checked and list-unhealthy-files), since the
1600 receiving client is expected to calculate those values itself from the
1601 stream of per-object check-and-repair-results.
1603 Note that the "ERROR:" indication will only be emitted if traversal stops,
1604 which will only occur if an unrecoverable directory is encountered. If a
1605 file or directory repair fails, the traversal will continue, and the repair
1606 failure will be indicated in the JSON data (in the "repair-successful" key).
1608 ``POST $DIRURL?t=start-manifest`` (must add &ophandle=XYZ)
1610 This operation generates a "manfest" of the given directory tree, mostly
1611 for debugging. This is a table of (path, filecap/dircap), for every object
1612 reachable from the starting directory. The path will be slash-joined, and
1613 the filecap/dircap will contain a link to the object in question. This page
1614 gives immediate access to every object in the virtual filesystem subtree.
1616 This operation uses the same ophandle= mechanism as deep-check. The
1617 corresponding /operations/$HANDLE page has three different forms. The
1618 default is output=HTML.
1620 If output=text is added to the query args, the results will be a text/plain
1621 list. The first line is special: it is either "finished: yes" or "finished:
1622 no"; if the operation is not finished, you must periodically reload the
1623 page until it completes. The rest of the results are a plaintext list, with
1624 one file/dir per line, slash-separated, with the filecap/dircap separated
1627 If output=JSON is added to the queryargs, then the results will be a
1628 JSON-formatted dictionary with six keys. Note that because large directory
1629 structures can result in very large JSON results, the full results will not
1630 be available until the operation is complete (i.e. until output["finished"]
1633 finished (bool): if False then you must reload the page until True
1634 origin_si (base32 str): the storage index of the starting point
1635 manifest: list of (path, cap) tuples, where path is a list of strings.
1636 verifycaps: list of (printable) verify cap strings
1637 storage-index: list of (base32) storage index strings
1638 stats: a dictionary with the same keys as the t=start-deep-stats command
1641 ``POST $DIRURL?t=start-deep-size`` (must add &ophandle=XYZ)
1643 This operation generates a number (in bytes) containing the sum of the
1644 filesize of all directories and immutable files reachable from the given
1645 directory. This is a rough lower bound of the total space consumed by this
1646 subtree. It does not include space consumed by mutable files, nor does it
1647 take expansion or encoding overhead into account. Later versions of the
1648 code may improve this estimate upwards.
1650 The /operations/$HANDLE status output consists of two lines of text::
1655 ``POST $DIRURL?t=start-deep-stats`` (must add &ophandle=XYZ)
1657 This operation performs a recursive walk of all files and directories
1658 reachable from the given directory, and generates a collection of
1659 statistics about those objects.
1661 The result (obtained from the /operations/$OPHANDLE page) is a
1662 JSON-serialized dictionary with the following keys (note that some of these
1663 keys may be missing until 'finished' is True)::
1665 finished: (bool) True if the operation has finished, else False
1666 count-immutable-files: count of how many CHK files are in the set
1667 count-mutable-files: same, for mutable files (does not include directories)
1668 count-literal-files: same, for LIT files (data contained inside the URI)
1669 count-files: sum of the above three
1670 count-directories: count of directories
1671 count-unknown: count of unrecognized objects (perhaps from the future)
1672 size-immutable-files: total bytes for all CHK files in the set, =deep-size
1673 size-mutable-files (TODO): same, for current version of all mutable files
1674 size-literal-files: same, for LIT files
1675 size-directories: size of directories (includes size-literal-files)
1676 size-files-histogram: list of (minsize, maxsize, count) buckets,
1677 with a histogram of filesizes, 5dB/bucket,
1678 for both literal and immutable files
1679 largest-directory: number of children in the largest directory
1680 largest-immutable-file: number of bytes in the largest CHK file
1682 size-mutable-files is not implemented, because it would require extra
1683 queries to each mutable file to get their size. This may be implemented in
1686 Assuming no sharing, the basic space consumed by a single root directory is
1687 the sum of size-immutable-files, size-mutable-files, and size-directories.
1688 The actual disk space used by the shares is larger, because of the
1689 following sources of overhead::
1692 expansion due to erasure coding
1693 share management data (leases)
1694 backend (ext3) minimum block size
1696 ``POST $URL?t=stream-manifest``
1698 This operation performs a recursive walk of all files and directories
1699 reachable from the given starting point. For each such unique object
1700 (duplicates are skipped), a single line of JSON is emitted to the HTTP
1701 response channel (or an error indication, see below). When the walk is
1702 complete, a final line of JSON is emitted which contains the accumulated
1703 file-size/count "deep-stats" data.
1705 A CLI tool can split the response stream on newlines into "response units",
1706 and parse each response unit as JSON. Each such parsed unit will be a
1707 dictionary, and will contain at least the "type" key: a string, one of
1708 "file", "directory", or "stats".
1710 For all units that have a type of "file" or "directory", the dictionary will
1711 contain the following keys::
1713 "path": a list of strings, with the path that is traversed to reach the
1715 "cap": a write-cap URI for the file or directory, if available, else a
1717 "verifycap": a verify-cap URI for the file or directory
1718 "repaircap": an URI for the weakest cap that can still be used to repair
1720 "storage-index": a base32 storage index for the object
1722 Note that non-distributed files (i.e. LIT files) will have values of None
1723 for verifycap, repaircap, and storage-index, since these files can neither
1724 be verified nor repaired, and are not stored on the storage servers.
1726 The last unit in the stream will have a type of "stats", and will contain
1727 the keys described in the "start-deep-stats" operation, below.
1729 If any errors occur during the traversal (specifically if a directory is
1730 unrecoverable, such that further traversal is not possible), an error
1731 indication is written to the response body, instead of the usual line of
1732 JSON. This error indication line will begin with the string "ERROR:" (in all
1733 caps), and contain a summary of the error on the rest of the line. The
1734 remaining lines of the response body will be a python exception. The client
1735 application should look for the ERROR: and stop processing JSON as soon as
1736 it is seen. The line just before the ERROR: will describe the directory that
1737 was untraversable, since the manifest entry is emitted to the HTTP response
1738 body before the child is traversed.
1744 The portion of the web namespace that begins with "/uri" (and "/named") is
1745 dedicated to giving users (both humans and programs) access to the Tahoe
1746 virtual filesystem. The rest of the namespace provides status information
1747 about the state of the Tahoe node.
1749 ``GET /`` (the root page)
1751 This is the "Welcome Page", and contains a few distinct sections::
1753 Node information: library versions, local nodeid, services being provided.
1755 Filesystem Access Forms: create a new directory, view a file/directory by
1756 URI, upload a file (unlinked), download a file by
1759 Grid Status: introducer information, helper information, connected storage
1764 This page lists all active uploads and downloads, and contains a short list
1765 of recent upload/download operations. Each operation has a link to a page
1766 that describes file sizes, servers that were involved, and the time consumed
1767 in each phase of the operation.
1769 A GET of /status/?t=json will contain a machine-readable subset of the same
1770 data. It returns a JSON-encoded dictionary. The only key defined at this
1771 time is "active", with a value that is a list of operation dictionaries, one
1772 for each active operation. Once an operation is completed, it will no longer
1773 appear in data["active"] .
1775 Each op-dict contains a "type" key, one of "upload", "download",
1776 "mapupdate", "publish", or "retrieve" (the first two are for immutable
1777 files, while the latter three are for mutable files and directories).
1779 The "upload" op-dict will contain the following keys::
1781 type (string): "upload"
1782 storage-index-string (string): a base32-encoded storage index
1783 total-size (int): total size of the file
1784 status (string): current status of the operation
1785 progress-hash (float): 1.0 when the file has been hashed
1786 progress-ciphertext (float): 1.0 when the file has been encrypted.
1787 progress-encode-push (float): 1.0 when the file has been encoded and
1788 pushed to the storage servers. For helper
1789 uploads, the ciphertext value climbs to 1.0
1790 first, then encoding starts. For unassisted
1791 uploads, ciphertext and encode-push progress
1792 will climb at the same pace.
1794 The "download" op-dict will contain the following keys::
1796 type (string): "download"
1797 storage-index-string (string): a base32-encoded storage index
1798 total-size (int): total size of the file
1799 status (string): current status of the operation
1800 progress (float): 1.0 when the file has been fully downloaded
1802 Front-ends which want to report progress information are advised to simply
1803 average together all the progress-* indicators. A slightly more accurate
1804 value can be found by ignoring the progress-hash value (since the current
1805 implementation hashes synchronously, so clients will probably never see
1806 progress-hash!=1.0).
1808 ``GET /provisioning/``
1810 This page provides a basic tool to predict the likely storage and bandwidth
1811 requirements of a large Tahoe grid. It provides forms to input things like
1812 total number of users, number of files per user, average file size, number
1813 of servers, expansion ratio, hard drive failure rate, etc. It then provides
1814 numbers like how many disks per server will be needed, how many read
1815 operations per second should be expected, and the likely MTBF for files in
1816 the grid. This information is very preliminary, and the model upon which it
1817 is based still needs a lot of work.
1819 ``GET /helper_status/``
1821 If the node is running a helper (i.e. if [helper]enabled is set to True in
1822 tahoe.cfg), then this page will provide a list of all the helper operations
1823 currently in progress. If "?t=json" is added to the URL, it will return a
1824 JSON-formatted list of helper statistics, which can then be used to produce
1825 graphs to indicate how busy the helper is.
1827 ``GET /statistics/``
1829 This page provides "node statistics", which are collected from a variety of
1832 load_monitor: every second, the node schedules a timer for one second in
1833 the future, then measures how late the subsequent callback
1834 is. The "load_average" is this tardiness, measured in
1835 seconds, averaged over the last minute. It is an indication
1836 of a busy node, one which is doing more work than can be
1837 completed in a timely fashion. The "max_load" value is the
1838 highest value that has been seen in the last 60 seconds.
1840 cpu_monitor: every minute, the node uses time.clock() to measure how much
1841 CPU time it has used, and it uses this value to produce
1842 1min/5min/15min moving averages. These values range from 0%
1843 (0.0) to 100% (1.0), and indicate what fraction of the CPU
1844 has been used by the Tahoe node. Not all operating systems
1845 provide meaningful data to time.clock(): they may report 100%
1846 CPU usage at all times.
1848 uploader: this counts how many immutable files (and bytes) have been
1849 uploaded since the node was started
1851 downloader: this counts how many immutable files have been downloaded
1852 since the node was started
1854 publishes: this counts how many mutable files (including directories) have
1855 been modified since the node was started
1857 retrieves: this counts how many mutable files (including directories) have
1858 been read since the node was started
1860 There are other statistics that are tracked by the node. The "raw stats"
1861 section shows a formatted dump of all of them.
1863 By adding "?t=json" to the URL, the node will return a JSON-formatted
1864 dictionary of stats values, which can be used by other tools to produce
1865 graphs of node behavior. The misc/munin/ directory in the source
1866 distribution provides some tools to produce these graphs.
1868 ``GET /`` (introducer status)
1870 For Introducer nodes, the welcome page displays information about both
1871 clients and servers which are connected to the introducer. Servers make
1872 "service announcements", and these are listed in a table. Clients will
1873 subscribe to hear about service announcements, and these subscriptions are
1874 listed in a separate table. Both tables contain information about what
1875 version of Tahoe is being run by the remote node, their advertised and
1876 outbound IP addresses, their nodeid and nickname, and how long they have
1879 By adding "?t=json" to the URL, the node will return a JSON-formatted
1880 dictionary of stats values, which can be used to produce graphs of connected
1881 clients over time. This dictionary has the following keys::
1883 ["subscription_summary"] : a dictionary mapping service name (like
1884 "storage") to an integer with the number of
1885 clients that have subscribed to hear about that
1887 ["announcement_summary"] : a dictionary mapping service name to an integer
1888 with the number of servers which are announcing
1890 ["announcement_distinct_hosts"] : a dictionary mapping service name to an
1891 integer which represents the number of
1892 distinct hosts that are providing that
1893 service. If two servers have announced
1894 FURLs which use the same hostnames (but
1895 different ports and tubids), they are
1896 considered to be on the same host.
1899 Static Files in /public_html
1900 ============================
1902 The web-API server will take any request for a URL that starts with /static
1903 and serve it from a configurable directory which defaults to
1904 $BASEDIR/public_html . This is configured by setting the "[node]web.static"
1905 value in $BASEDIR/tahoe.cfg . If this is left at the default value of
1906 "public_html", then http://localhost:3456/static/subdir/foo.html will be
1907 served with the contents of the file $BASEDIR/public_html/subdir/foo.html .
1909 This can be useful to serve a javascript application which provides a
1910 prettier front-end to the rest of the Tahoe web-API.
1913 Safety and Security Issues -- Names vs. URIs
1914 ============================================
1916 Summary: use explicit file- and dir- caps whenever possible, to reduce the
1917 potential for surprises when the filesystem structure is changed.
1919 Tahoe provides a mutable filesystem, but the ways that the filesystem can
1920 change are limited. The only thing that can change is that the mapping from
1921 child names to child objects that each directory contains can be changed by
1922 adding a new child name pointing to an object, removing an existing child name,
1923 or changing an existing child name to point to a different object.
1925 Obviously if you query Tahoe for information about the filesystem and then act
1926 to change the filesystem (such as by getting a listing of the contents of a
1927 directory and then adding a file to the directory), then the filesystem might
1928 have been changed after you queried it and before you acted upon it. However,
1929 if you use the URI instead of the pathname of an object when you act upon the
1930 object, then the only change that can happen is if the object is a directory
1931 then the set of child names it has might be different. If, on the other hand,
1932 you act upon the object using its pathname, then a different object might be in
1933 that place, which can result in more kinds of surprises.
1935 For example, suppose you are writing code which recursively downloads the
1936 contents of a directory. The first thing your code does is fetch the listing
1937 of the contents of the directory. For each child that it fetched, if that
1938 child is a file then it downloads the file, and if that child is a directory
1939 then it recurses into that directory. Now, if the download and the recurse
1940 actions are performed using the child's name, then the results might be
1941 wrong, because for example a child name that pointed to a sub-directory when
1942 you listed the directory might have been changed to point to a file (in which
1943 case your attempt to recurse into it would result in an error and the file
1944 would be skipped), or a child name that pointed to a file when you listed the
1945 directory might now point to a sub-directory (in which case your attempt to
1946 download the child would result in a file containing HTML text describing the
1949 If your recursive algorithm uses the uri of the child instead of the name of
1950 the child, then those kinds of mistakes just can't happen. Note that both the
1951 child's name and the child's URI are included in the results of listing the
1952 parent directory, so it isn't any harder to use the URI for this purpose.
1954 The read and write caps in a given directory node are separate URIs, and
1955 can't be assumed to point to the same object even if they were retrieved in
1956 the same operation (although the web-API server attempts to ensure this
1957 in most cases). If you need to rely on that property, you should explicitly
1958 verify it. More generally, you should not make assumptions about the
1959 internal consistency of the contents of mutable directories. As a result
1960 of the signatures on mutable object versions, it is guaranteed that a given
1961 version was written in a single update, but -- as in the case of a file --
1962 the contents may have been chosen by a malicious writer in a way that is
1963 designed to confuse applications that rely on their consistency.
1965 In general, use names if you want "whatever object (whether file or
1966 directory) is found by following this name (or sequence of names) when my
1967 request reaches the server". Use URIs if you want "this particular object".
1973 Tahoe uses both mutable and immutable files. Mutable files can be created
1974 explicitly by doing an upload with ?mutable=true added, or implicitly by
1975 creating a new directory (since a directory is just a special way to
1976 interpret a given mutable file).
1978 Mutable files suffer from the same consistency-vs-availability tradeoff that
1979 all distributed data storage systems face. It is not possible to
1980 simultaneously achieve perfect consistency and perfect availability in the
1981 face of network partitions (servers being unreachable or faulty).
1983 Tahoe tries to achieve a reasonable compromise, but there is a basic rule in
1984 place, known as the Prime Coordination Directive: "Don't Do That". What this
1985 means is that if write-access to a mutable file is available to several
1986 parties, then those parties are responsible for coordinating their activities
1987 to avoid multiple simultaneous updates. This could be achieved by having
1988 these parties talk to each other and using some sort of locking mechanism, or
1989 by serializing all changes through a single writer.
1991 The consequences of performing uncoordinated writes can vary. Some of the
1992 writers may lose their changes, as somebody else wins the race condition. In
1993 many cases the file will be left in an "unhealthy" state, meaning that there
1994 are not as many redundant shares as we would like (reducing the reliability
1995 of the file against server failures). In the worst case, the file can be left
1996 in such an unhealthy state that no version is recoverable, even the old ones.
1997 It is this small possibility of data loss that prompts us to issue the Prime
1998 Coordination Directive.
2000 Tahoe nodes implement internal serialization to make sure that a single Tahoe
2001 node cannot conflict with itself. For example, it is safe to issue two
2002 directory modification requests to a single tahoe node's web-API server at the
2003 same time, because the Tahoe node will internally delay one of them until
2004 after the other has finished being applied. (This feature was introduced in
2005 Tahoe-1.1; back with Tahoe-1.0 the web client was responsible for serializing
2006 web requests themselves).
2008 For more details, please see the "Consistency vs Availability" and "The Prime
2009 Coordination Directive" sections of `mutable.rst <../specifications/mutable.rst>`_.
2015 Gateway nodes may find it necessary to prohibit access to certain files. The
2016 web-API has a facility to block access to filecaps by their storage index,
2017 returning a 403 "Forbidden" error instead of the original file.
2019 This blacklist is recorded in $NODEDIR/access.blacklist, and contains one
2020 blocked file per line. Comment lines (starting with ``#``) are ignored. Each
2021 line consists of the storage-index (in the usual base32 format as displayed
2022 by the "More Info" page, or by the "tahoe debug dump-cap" command), followed
2023 by whitespace, followed by a reason string, which will be included in the 403
2024 error message. This could hold a URL to a page that explains why the file is
2025 blocked, for example.
2027 So for example, if you found a need to block access to a file with filecap
2028 ``URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861``,
2029 you could do the following::
2031 tahoe debug dump-cap URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2032 -> storage index: whpepioyrnff7orecjolvbudeu
2033 echo "whpepioyrnff7orecjolvbudeu my puppy told me to" >>$NODEDIR/access.blacklist
2034 tahoe restart $NODEDIR
2035 tahoe get URI:CHK:n7r3m6wmomelk4sep3kw5cvduq:os7ijw5c3maek7pg65e5254k2fzjflavtpejjyhshpsxuqzhcwwq:3:20:14861
2036 -> error, 403 Access Prohibited: my puppy told me to
2038 The ``access.blacklist`` file will be checked each time a file or directory
2039 is accessed: the file's ``mtime`` is used to decide whether it need to be
2040 reloaded. Therefore no node restart is necessary when creating the initial
2041 blacklist, nor when adding second, third, or additional entries to the list.
2042 When modifying the file, be careful to update it atomically, otherwise a
2043 request may arrive while the file is only halfway written, and the partial
2044 file may be incorrectly parsed.
2046 The blacklist is applied to all access paths (including FTP, SFTP, and CLI
2047 operations), not just the web-API. The blacklist also applies to directories.
2048 If a directory is blacklisted, the gateway will refuse access to both that
2049 directory and any child files/directories underneath it, when accessed via
2050 "DIRCAP/SUBDIR/FILENAME" -style URLs. Users who go directly to the child
2051 file/dir will bypass the blacklist.
2053 The node will log the SI of the file being blocked, and the reason code, into
2054 the ``logs/twistd.log`` file.
2057 .. [1] URLs and HTTP and UTF-8, Oh My
2059 HTTP does not provide a mechanism to specify the character set used to
2060 encode non-ASCII names in URLs
2061 (`RFC3986#2.1 <http://tools.ietf.org/html/rfc3986#section-2.1>`_).
2062 We prefer the convention that the ``filename=`` argument shall be a
2063 URL-escaped UTF-8 encoded Unicode string.
2064 For example, suppose we want to provoke the server into using a filename of
2065 "f i a n c e-acute e" (i.e. f i a n c U+00E9 e). The UTF-8 encoding of this
2066 is 0x66 0x69 0x61 0x6e 0x63 0xc3 0xa9 0x65 (or "fianc\\xC3\\xA9e", as python's
2067 ``repr()`` function would show). To encode this into a URL, the non-printable
2068 characters must be escaped with the urlencode ``%XX`` mechanism, giving
2069 us "fianc%C3%A9e". Thus, the first line of the HTTP request will be
2070 "``GET /uri/CAP...?save=true&filename=fianc%C3%A9e HTTP/1.1``". Not all
2071 browsers provide this: IE7 by default uses the Latin-1 encoding, which is
2072 "fianc%E9e" (although it has a configuration option to send URLs as UTF-8).
2074 The response header will need to indicate a non-ASCII filename. The actual
2075 mechanism to do this is not clear. For ASCII filenames, the response header
2078 Content-Disposition: attachment; filename="english.txt"
2080 If Tahoe were to enforce the UTF-8 convention, it would need to decode the
2081 URL argument into a Unicode string, and then encode it back into a sequence
2082 of bytes when creating the response header. One possibility would be to use
2083 unencoded UTF-8. Developers suggest that IE7 might accept this::
2085 #1: Content-Disposition: attachment; filename="fianc\xC3\xA9e"
2086 (note, the last four bytes of that line, not including the newline, are
2087 0xC3 0xA9 0x65 0x22)
2089 `RFC2231#4 <http://tools.ietf.org/html/rfc2231#section-4>`_
2090 (dated 1997): suggests that the following might work, and
2091 `some developers have reported <http://markmail.org/message/dsjyokgl7hv64ig3>`_
2092 that it is supported by Firefox (but not IE7)::
2094 #2: Content-Disposition: attachment; filename*=utf-8''fianc%C3%A9e
2096 My reading of `RFC2616#19.5.1 <http://tools.ietf.org/html/rfc2616#section-19.5.1>`_
2097 (which defines Content-Disposition) says that the filename= parameter is
2098 defined to be wrapped in quotes (presumably to allow spaces without breaking
2099 the parsing of subsequent parameters), which would give us::
2101 #3: Content-Disposition: attachment; filename*=utf-8''"fianc%C3%A9e"
2103 However this is contrary to the examples in the email thread listed above.
2105 Developers report that IE7 (when it is configured for UTF-8 URL encoding,
2106 which is not the default in Asian countries), will accept::
2108 #4: Content-Disposition: attachment; filename=fianc%C3%A9e
2110 However, for maximum compatibility, Tahoe simply copies bytes from the URL
2111 into the response header, rather than enforcing the UTF-8 convention. This
2112 means it does not try to decode the filename from the URL argument, nor does
2113 it encode the filename into the response header.