2 = The Tahoe REST-ful Web API =
4 1. Enabling the web-API port
5 2. Basic Concepts: GET, PUT, DELETE, POST
6 3. URLs, Machine-Oriented Interfaces
7 4. Browser Operations: Human-Oriented Interfaces
8 5. Welcome / Debug / Status pages
9 6. Static Files in /public_html
10 7. Safety and security issues -- names vs. URIs
14 == Enabling the web-API port ==
16 Every Tahoe node is capable of running a built-in HTTP server. To enable
17 this, just write a port number into the "[node]web.port" line of your node's
18 tahoe.cfg file. For example, writing "web.port = 3456" into the "[node]"
19 section of $NODEDIR/tahoe.cfg will cause the node to run a webserver on port
22 This string is actually a Twisted "strports" specification, meaning you can
23 get more control over the interface to which the server binds by supplying
24 additional arguments. For more details, see the documentation on
25 twisted.application.strports:
26 http://twistedmatrix.com/documents/current/api/twisted.application.strports.html
28 Writing "tcp:3456:interface=127.0.0.1" into the web.port line does the same
29 but binds to the loopback interface, ensuring that only the programs on the
30 local host can connect. Using
31 "ssl:3456:privateKey=mykey.pem:certKey=cert.pem" runs an SSL server.
33 This webport can be set when the node is created by passing a --webport
34 option to the 'tahoe create-node' command. By default, the node listens on
35 port 3456, on the loopback (127.0.0.1) interface.
39 As described in architecture.txt, each file and directory in a Tahoe virtual
40 filesystem is referenced by an identifier that combines the designation of
41 the object with the authority to do something with it (such as read or modify
42 the contents). This identifier is called a "read-cap" or "write-cap",
43 depending upon whether it enables read-only or read-write access. These
44 "caps" are also referred to as URIs.
46 The Tahoe web-based API is "REST-ful", meaning it implements the concepts of
47 "REpresentational State Transfer": the original scheme by which the World
48 Wide Web was intended to work. Each object (file or directory) is referenced
49 by a URL that includes the read- or write- cap. HTTP methods (GET, PUT, and
50 DELETE) are used to manipulate these objects. You can think of the URL as a
51 noun, and the method as a verb.
53 In REST, the GET method is used to retrieve information about an object, or
54 to retrieve some representation of the object itself. When the object is a
55 file, the basic GET method will simply return the contents of that file.
56 Other variations (generally implemented by adding query parameters to the
57 URL) will return information about the object, such as metadata. GET
58 operations are required to have no side-effects.
60 PUT is used to upload new objects into the filesystem, or to replace an
61 existing object. DELETE it used to delete objects from the filesystem. Both
62 PUT and DELETE are required to be idempotent: performing the same operation
63 multiple times must have the same side-effects as only performing it once.
65 POST is used for more complicated actions that cannot be expressed as a GET,
66 PUT, or DELETE. POST operations can be thought of as a method call: sending
67 some message to the object referenced by the URL. In Tahoe, POST is also used
68 for operations that must be triggered by an HTML form (including upload and
69 delete), because otherwise a regular web browser has no way to accomplish
70 these tasks. In general, everything that can be done with a PUT or DELETE can
71 also be done with a POST.
73 Tahoe's web API is designed for two different consumers. The first is a
74 program that needs to manipulate the virtual file system. Such programs are
75 expected to use the RESTful interface described above. The second is a human
76 using a standard web browser to work with the filesystem. This user is given
77 a series of HTML pages with links to download files, and forms that use POST
78 actions to upload, rename, and delete files.
80 When an error occurs, the HTTP response code will be set to an appropriate
81 400-series code (like 404 for an unknown childname, or 400 Gone when a file
82 is unrecoverable due to insufficient shares), and the HTTP response body will
83 usually contain a few lines of explanation as to the cause of the error and
84 possible responses. Unusual exceptions may result in a 500 Internal Server
85 Error as a catch-all, with a default response body will contain a
86 Nevow-generated HTML-ized representation of the Python exception stack trace
87 that caused the problem. CLI programs which want to copy the response body to
88 stderr should provide an "Accept: text/plain" header to their requests to get
89 a plain text stack trace instead. If the Accept header contains */*, or
90 text/*, or text/html (or if there is no Accept header), HTML tracebacks will
95 Tahoe uses a variety of read- and write- caps to identify files and
96 directories. The most common of these is the "immutable file read-cap", which
97 is used for most uploaded files. These read-caps look like the following:
99 URI:CHK:ime6pvkaxuetdfah2p2f35pe54:4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a:3:10:202
101 The next most common is a "directory write-cap", which provides both read and
102 write access to a directory, and look like this:
104 URI:DIR2:djrdkfawoqihigoett4g6auz6a:jx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq
106 There are also "directory read-caps", which start with "URI:DIR2-RO:", and
107 give read-only access to a directory. Finally there are also mutable file
108 read- and write- caps, which start with "URI:SSK", and give access to mutable
111 (later versions of Tahoe will make these strings shorter, and will remove the
112 unfortunate colons, which must be escaped when these caps are embedded in
115 To refer to any Tahoe object through the web API, you simply need to combine
116 a prefix (which indicates the HTTP server to use) with the cap (which
117 indicates which object inside that server to access). Since the default Tahoe
118 webport is 3456, the most common prefix is one that will use a local node
119 listening on this port:
121 http://127.0.0.1:3456/uri/ + $CAP
123 So, to access the directory named above (which happens to be the
124 publically-writable sample directory on the Tahoe test grid, described at
125 http://allmydata.org/trac/tahoe/wiki/TestGrid), the URL would be:
127 http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/
129 (note that the colons in the directory-cap are url-encoded into "%3A"
132 Likewise, to access the file named above, use:
134 http://127.0.0.1:3456/uri/URI%3ACHK%3Aime6pvkaxuetdfah2p2f35pe54%3A4btz54xk3tew6nd4y2ojpxj4m6wxjqqlwnztgre6gnjgtucd5r4a%3A3%3A10%3A202
136 In the rest of this document, we'll use "$DIRCAP" as shorthand for a read-cap
137 or write-cap that refers to a directory, and "$FILECAP" to abbreviate a cap
138 that refers to a file (whether mutable or immutable). So those URLs above can
141 http://127.0.0.1:3456/uri/$DIRCAP/
142 http://127.0.0.1:3456/uri/$FILECAP
144 The operation summaries below will abbreviate these further, by eliding the
145 server prefix. They will be displayed like this:
153 Tahoe directories contain named children, just like directories in a regular
154 local filesystem. These children can be either files or subdirectories.
156 If you have a Tahoe URL that refers to a directory, and want to reference a
157 named child inside it, just append the child name to the URL. For example, if
158 our sample directory contains a file named "welcome.txt", we can refer to
161 http://127.0.0.1:3456/uri/$DIRCAP/welcome.txt
163 (or http://127.0.0.1:3456/uri/URI%3ADIR2%3Adjrdkfawoqihigoett4g6auz6a%3Ajx5mplfpwexnoqff7y5e4zjus4lidm76dcuarpct7cckorh2dpgq/welcome.txt)
165 Multiple levels of subdirectories can be handled this way:
167 http://127.0.0.1:3456/uri/$DIRCAP/tahoe-source/docs/webapi.txt
169 In this document, when we need to refer to a URL that references a file using
170 this child-of-some-directory format, we'll use the following string:
172 /uri/$DIRCAP/[SUBDIRS../]FILENAME
174 The "[SUBDIRS../]" part means that there are zero or more (optional)
175 subdirectory names in the middle of the URL. The "FILENAME" at the end means
176 that this whole URL refers to a file of some sort, rather than to a
179 When we need to refer specifically to a directory in this way, we'll write:
181 /uri/$DIRCAP/[SUBDIRS../]SUBDIR
184 Note that all components of pathnames in URLs are required to be UTF-8
185 encoded, so "resume.doc" (with an acute accent on both E's) would be accessed
188 http://127.0.0.1:3456/uri/$DIRCAP/r%C3%A9sum%C3%A9.doc
190 Also note that the filenames inside upload POST forms are interpreted using
191 whatever character set was provided in the conventional '_charset' field, and
192 defaults to UTF-8 if not otherwise specified. The JSON representation of each
193 directory contains native unicode strings. Tahoe directories are specified to
194 contain unicode filenames, and cannot contain binary strings that are not
195 representable as such.
197 All Tahoe operations that refer to existing files or directories must include
198 a suitable read- or write- cap in the URL: the wapi server won't add one
199 for you. If you don't know the cap, you can't access the file. This allows
200 the security properties of Tahoe caps to be extended across the wapi
203 == Slow Operations, Progress, and Cancelling ==
205 Certain operations can be expected to take a long time. The "t=deep-check",
206 described below, will recursively visit every file and directory reachable
207 from a given starting point, which can take minutes or even hours for
208 extremely large directory structures. A single long-running HTTP request is a
209 fragile thing: proxies, NAT boxes, browsers, and users may all grow impatient
210 with waiting and give up on the connection.
212 For this reason, long-running operations have an "operation handle", which
213 can be used to poll for status/progress messages while the operation
214 proceeds. This handle can also be used to cancel the operation. These handles
215 are created by the client, and passed in as a an "ophandle=" query argument
216 to the POST or PUT request which starts the operation. The following
217 operations can then be used to retrieve status:
219 GET /operations/$HANDLE?output=HTML (with or without t=status)
220 GET /operations/$HANDLE?output=JSON (same)
222 These two retrieve the current status of the given operation. Each operation
223 presents a different sort of information, but in general the page retrieved
226 * whether the operation is complete, or if it is still running
227 * how much of the operation is complete, and how much is left, if possible
229 Note that the final status output can be quite large: a deep-manifest of a
230 directory structure with 300k directories and 200k unique files is about
231 275MB of JSON, and might take two minutes to generate. For this reason, the
232 full status is not provided until the operation has completed.
234 The HTML form will include a meta-refresh tag, which will cause a regular
235 web browser to reload the status page about 60 seconds later. This tag will
236 be removed once the operation has completed.
238 There may be more status information available under
239 /operations/$HANDLE/$ETC : i.e., the handle forms the root of a URL space.
241 POST /operations/$HANDLE?t=cancel
243 This terminates the operation, and returns an HTML page explaining what was
244 cancelled. If the operation handle has already expired (see below), this
245 POST will return a 404, which indicates that the operation is no longer
246 running (either it was completed or terminated). The response body will be
247 the same as a GET /operations/$HANDLE on this operation handle, and the
248 handle will be expired immediately afterwards.
250 The operation handle will eventually expire, to avoid consuming an unbounded
251 amount of memory. The handle's time-to-live can be reset at any time, by
252 passing a retain-for= argument (with a count of seconds) to either the
253 initial POST that starts the operation, or the subsequent GET request which
254 asks about the operation. For example, if a 'GET
255 /operations/$HANDLE?output=JSON&retain-for=600' query is performed, the
256 handle will remain active for 600 seconds (10 minutes) after the GET was
259 In addition, if the GET includes a release-after-complete=True argument, and
260 the operation has completed, the operation handle will be released
263 If a retain-for= argument is not used, the default handle lifetimes are:
265 * handles will remain valid at least until their operation finishes
266 * uncollected handles for finished operations (i.e. handles for operations
267 which have finished but for which the GET page has not been accessed since
268 completion) will remain valid for one hour, or for the total time consumed
269 by the operation, whichever is greater.
270 * collected handles (i.e. the GET page has been retrieved at least once
271 since the operation completed) will remain valid for ten minutes.
273 Many "slow" operations can begin to use unacceptable amounts of memory when
274 operation on large directory structures. The memory usage increases when the
275 ophandle is polled, as the results must be copied into a JSON string, sent
276 over the wire, then parsed by a client. So, as an alternative, many "slow"
277 operations have streaming equivalents. These equivalents do not use operation
278 handles. Instead, they emit line-oriented status results immediately. Client
279 code can cancel the operation by simply closing the HTTP connection.
281 == Programmatic Operations ==
283 Now that we know how to build URLs that refer to files and directories in a
284 Tahoe virtual filesystem, what sorts of operations can we do with those URLs?
285 This section contains a catalog of GET, PUT, DELETE, and POST operations that
286 can be performed on these URLs. This set of operations are aimed at programs
287 that use HTTP to communicate with a Tahoe node. A later section describes
288 operations that are intended for web browsers.
290 === Reading A File ===
293 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME
295 This will retrieve the contents of the given file. The HTTP response body
296 will contain the sequence of bytes that make up the file.
298 To view files in a web browser, you may want more control over the
299 Content-Type and Content-Disposition headers. Please see the next section
300 "Browser Operations", for details on how to modify these URLs for that
303 === Writing/Uploading A File ===
306 PUT /uri/$DIRCAP/[SUBDIRS../]FILENAME
308 Upload a file, using the data from the HTTP request body, and add whatever
309 child links and subdirectories are necessary to make the file available at
310 the given location. Once this operation succeeds, a GET on the same URL will
311 retrieve the same contents that were just uploaded. This will create any
312 necessary intermediate subdirectories.
314 To use the /uri/$FILECAP form, $FILECAP be a write-cap for a mutable file.
316 In the /uri/$DIRCAP/[SUBDIRS../]FILENAME form, if the target file is a
317 writable mutable file, that files contents will be overwritten in-place. If
318 it is a read-cap for a mutable file, an error will occur. If it is an
319 immutable file, the old file will be discarded, and a new one will be put in
322 When creating a new file, if "mutable=true" is in the query arguments, the
323 operation will create a mutable file instead of an immutable one.
325 This returns the file-cap of the resulting file. If a new file was created
326 by this method, the HTTP response code (as dictated by rfc2616) will be set
327 to 201 CREATED. If an existing file was replaced or modified, the response
330 Note that the 'curl -T localfile http://127.0.0.1:3456/uri/$DIRCAP/foo.txt'
331 command can be used to invoke this operation.
335 This uploads a file, and produces a file-cap for the contents, but does not
336 attach the file into the virtual drive. No directories will be modified by
337 this operation. The file-cap is returned as the body of the HTTP response.
339 If "mutable=true" is in the query arguments, the operation will create a
340 mutable file, and return its write-cap in the HTTP respose. The default is
341 to create an immutable file, returning the read-cap as a response.
343 === Creating A New Directory ===
348 Create a new empty directory and return its write-cap as the HTTP response
349 body. This does not make the newly created directory visible from the
350 virtual drive. The "PUT" operation is provided for backwards compatibility:
351 new code should use POST.
353 POST /uri?t=mkdir-with-children
355 Create a new directory, populated with a set of child nodes, and return its
356 write-cap as the HTTP response body. The new directory is not attached to
357 any other directory: the returned write-cap is the only reference to it.
359 Initial children are provided as the body of the POST form (this is more
360 efficient than doing separate mkdir and set_children operations). If the
361 body is empty, the new directory will be empty. If not empty, the body will
362 be interpreted as a UTF-8 JSON-encoded dictionary of children with which the
363 new directory should be populated, using the same format as would be
364 returned in the 'children' value of the t=json GET request, described below.
365 Each dictionary key should be a child name, and each value should be a list
366 of [TYPE, PROPDICT], where PROPDICT contains "rw_uri", "ro_uri", and
367 "metadata" keys (all others are ignored). For example, the PUT request body
371 "Fran\u00e7ais": [ "filenode", {
372 "ro_uri": "URI:CHK:...",
375 "ctime": 1202777696.7564139,
376 "mtime": 1202777696.7564139,
378 "linkcrtime": 1202777696.7564139,
379 "linkmotime": 1202777696.7564139,
381 "subdir": [ "dirnode", {
382 "rw_uri": "URI:DIR2:...",
383 "ro_uri": "URI:DIR2-RO:...",
385 "ctime": 1202778102.7589991,
386 "mtime": 1202778111.2160511,
388 "linkcrtime": 1202777696.7564139,
389 "linkmotime": 1202777696.7564139,
393 Note that the webapi-using client application must not provide the
394 "Content-Type: multipart/form-data" header that usually accompanies HTML
395 form submissions, since the body is not formatted this way. Doing so will
396 cause a server error as the lower-level code misparses the request body.
398 Child file names should each be expressed as a unicode string, then used as
399 keys of the dictionary. The dictionary should then be converted into JSON,
400 and the resulting string encoded into UTF-8. This UTF-8 bytestring should
401 then be used as the POST body.
403 POST /uri?t=mkdir-immutable
405 Like t=mkdir-with-children above, but the new directory will be
406 deep-immutable. This means that the directory itself is immutable, and that
407 it can only contain deep-immutable objects, like immutable files, literal
408 files, and deep-immutable directories. A non-empty request body is
409 mandatory, since after the directory is created, it will not be possible to
410 add more children to it.
412 POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir
413 PUT /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir
415 Create new directories as necessary to make sure that the named target
416 ($DIRCAP/SUBDIRS../SUBDIR) is a directory. This will create additional
417 intermediate directories as necessary. If the named target directory already
418 exists, this will make no changes to it.
420 If the final directory is created, it will be empty.
422 This will return an error if a blocking file is present at any of the parent
423 names, preventing the server from creating the necessary parent directory.
425 The write-cap of the new directory will be returned as the HTTP response
428 POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-with-children
430 Like above, but if the final directory is created, it will be populated with
431 initial children from the POST request body, as described above in the
432 /uri?t=mkdir-with-children operation.
434 POST /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=mkdir-immutable
436 Like above, but the final directory will be deep-immutable, with the
437 children specified as a JSON dictionary in the POST request body.
439 POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=NAME
441 Create a new empty directory and attach it to the given existing directory.
442 This will create additional intermediate directories as necessary.
444 The URL of this form points to the parent of the bottom-most new directory,
445 whereas the previous form has a URL that points directly to the bottom-most
448 POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-with-children&name=NAME
450 As above, but the new directory will be populated with initial children via
451 the POST request body, as described in /uri?t=mkdir-with-children above.
452 Note that the name= argument must be passed as a queryarg, because the POST
453 request body is used for the initial children JSON.
455 POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir-immutable&name=NAME
457 As above, but the new directory will be deep-immutable, with the children
458 specified as a JSON dictionary in the POST request body. Again, the name=
459 argument must be passed as a queryarg.
461 === Get Information About A File Or Directory (as JSON) ===
463 GET /uri/$FILECAP?t=json
464 GET /uri/$DIRCAP?t=json
465 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json
466 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json
468 This returns a machine-parseable JSON-encoded description of the given
469 object. The JSON always contains a list, and the first element of the list is
470 always a flag that indicates whether the referenced object is a file or a
471 directory. If it is a capability to a file, then the information includes
472 file size and URI, like this:
474 GET /uri/$FILECAP?t=json :
478 "verify_uri": verify_uri,
483 If it is a capability to a directory followed by a path from that directory
484 to a file, then the information also includes metadata from the link to the
485 file in the parent directory, like this:
487 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=json :
491 "verify_uri": verify_uri,
495 "ctime": 1202777696.7564139,
496 "mtime": 1202777696.7564139,
498 "linkcrtime": 1202777696.7564139,
499 "linkmotime": 1202777696.7564139,
502 If it is a directory, then it includes information about the children of
503 this directory, as a mapping from child name to a set of data about the
504 child (the same data that would appear in a corresponding GET?t=json of the
505 child itself). The child entries also include metadata about each child,
506 including link-creation- and link-change- timestamps. The output looks like
509 GET /uri/$DIRCAP?t=json :
510 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR?t=json :
513 "rw_uri": read_write_uri,
514 "ro_uri": read_only_uri,
515 "verify_uri": verify_uri,
518 "foo.txt": [ "filenode", {
522 "ctime": 1202777696.7564139,
523 "mtime": 1202777696.7564139,
525 "linkcrtime": 1202777696.7564139,
526 "linkmotime": 1202777696.7564139,
528 "subdir": [ "dirnode", {
532 "ctime": 1202778102.7589991,
533 "mtime": 1202778111.2160511,
535 "linkcrtime": 1202777696.7564139,
536 "linkmotime": 1202777696.7564139,
540 In the above example, note how 'children' is a dictionary in which the keys
541 are child names and the values depend upon whether the child is a file or a
542 directory. The value is mostly the same as the JSON representation of the
543 child object (except that directories do not recurse -- the "children"
544 entry of the child is omitted, and the directory view includes the metadata
545 that is stored on the directory edge).
547 Then the rw_uri field will be present in the information about a directory
548 if and only if you have read-write access to that directory. The verify_uri
549 field will be presend if and only if the object has a verify-cap
550 (non-distributed LIT files do not have verify-caps).
552 ==== About the metadata ====
554 The value of the 'mtime' key and of the 'tahoe':'linkmotime' is updated
555 whenever a link to a child is set. The value of the 'ctime' key and of the
556 'tahoe':'linkcrtime' key is updated whenever a link to a child is created --
557 i.e. when there was not previously a link under that name.
559 In Tahoe earlier than v1.4.0, only the 'mtime'/'ctime' keys were populated.
560 Starting in Tahoe v1.4.0, the 'linkmotime'/'linkcrtime' keys in the 'tahoe'
561 sub-dict are also populated.
563 The reason we added the new values in Tahoe v1.4.0 is that there is a
564 "set_children" API (described below) which you can use to overwrite the
565 values of the 'mtime'/'ctime' pair, and this API is used by the "tahoe
566 backup" command (both in Tahoe v1.3.0 and in Tahoe v1.4.0) to set the
567 'mtime' and 'ctime' values when backing up files from a local filesystem
568 into the Tahoe filesystem. As of Tahoe v1.4.0, the set_children API cannot
569 be used to set anything under the 'tahoe' key of the metadata dict -- if
570 you include 'tahoe' keys in your 'metadata' arguments then it will silently
573 Therefore, if the 'tahoe' sub-dict is present, you can rely on the
574 'linkcrtime' and 'linkmotime' values therein to have the semantics described
575 above. (This is assuming that only official Tahoe clients have been used to
576 write those links, and that their system clocks were set to what you expected
577 -- there is nothing preventing someone from editing their Tahoe client or
578 writing their own Tahoe client which would overwrite those values however
579 they like, and there is nothing to constrain their system clock from taking
582 The meaning of the 'ctime'/'mtime' fields are slightly more complex.
584 The meaning of the 'mtime' field is: whenever the edge is updated (by an HTTP
585 PUT or POST, as is done by the "tahoe cp" command), then the mtime is set to
586 the current time on the clock of the updating client. Whenever the edge is
587 updated by "tahoe backup" then the mtime is instead set to the value which
588 the updating client read from its local filesystem for the "mtime" of the
589 local file in question, which means the last time the contents of that file
590 were changed. Note however, that if the edge in the Tahoe filesystem points
591 to a mutable file and the contents of that mutable file is changed then the
592 "mtime" value on that edge will *not* be updated, since the edge itself
593 wasn't updated -- only the mutable file was.
595 The meaning of the 'ctime' field is even more complex. Whenever a new edge is
596 created (by an HTTP PUT or POST, as is done by "tahoe cp") then the ctime is
597 set to the current time on the clock of the updating client. Whenever the
598 edge is created *or updated* by "tahoe backup" then the ctime is instead set
599 to the value which the updating client read from its local filesystem. On
600 Windows, it reads the timestamp of when the local file was created and puts
601 that into the "ctime", and on other platforms it reads the timestamp of the
602 most recent time that either the contents or the metadata of the local file
603 was changed and puts that into the ctime. Again, if the edge points to a
604 mutable file and the content of that mutable file is changed then the ctime
605 will not be updated in any case.
607 Therefore there are several ways that the 'ctime' field could be confusing:
609 1. You might be confused about whether it reflects the time of the creation
610 of a link in the Tahoe filesystem or a timestamp copied in from a local
613 2. You might be confused about whether it is a copy of the file creation time
614 (if "tahoe backup" was run on a Windows system) or of the last
615 contents-or-metadata change (if "tahoe backup" was run on a different
618 3. You might be confused by the fact that changing the contents of a mutable
619 file in Tahoe don't have any effect on any links pointing at that file in any
620 directories, although "tahoe backup" sets the link 'ctime'/'mtime' to reflect
621 timestamps about the local file corresponding to the Tahoe file to which the
624 4. Also, quite apart from Tahoe, you might be confused about the meaning of
625 the 'ctime' in unix local filesystems, which people sometimes think means
626 file creation time, but which actually means, in unix local filesystems, the
627 most recent time that the file contents or the file metadata (such as owner,
628 permission bits, extended attributes, etc.) has changed. Note that although
629 'ctime' does not mean file creation time in Unix, it does mean link creation
630 time in Tahoe, unless the "tahoe backup" command has been used on that link,
631 in which case it means something about the local filesystem file which
632 corresponds to the Tahoe file which is pointed at by the link. It means
633 either file creation time of the local file (if "tahoe backup" was run on
634 Windows) or file-contents-or-metadata-update-time of the local file (if
635 "tahoe backup" was run on a different operating system).
638 === Attaching an existing File or Directory by its read- or write- cap ===
640 PUT /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri
642 This attaches a child object (either a file or directory) to a specified
643 location in the virtual filesystem. The child object is referenced by its
644 read- or write- cap, as provided in the HTTP request body. This will create
645 intermediate directories as necessary.
647 This is similar to a UNIX hardlink: by referencing a previously-uploaded file
648 (or previously-created directory) instead of uploading/creating a new one,
649 you can create two references to the same object.
651 The read- or write- cap of the child is provided in the body of the HTTP
652 request, and this same cap is returned in the response body.
654 The default behavior is to overwrite any existing object at the same
655 location. To prevent this (and make the operation return an error instead
656 of overwriting), add a "replace=false" argument, as "?t=uri&replace=false".
657 With replace=false, this operation will return an HTTP 409 "Conflict" error
658 if there is already an object at the given location, rather than
659 overwriting the existing object. To allow the operation to overwrite a
660 file, but return an error when trying to overwrite a directory, use
661 "replace=only-files" (this behavior is closer to the traditional unix "mv"
662 command). Note that "true", "t", and "1" are all synonyms for "True", and
663 "false", "f", and "0" are synonyms for "False", and the parameter is
666 === Adding multiple files or directories to a parent directory at once ===
668 POST /uri/$DIRCAP/[SUBDIRS..]?t=set_children
670 This command adds multiple children to a directory in a single operation.
671 It reads the request body and interprets it as a JSON-encoded description
672 of the child names and read/write-caps that should be added.
674 The body should be a JSON-encoded dictionary, in the same format as the
675 "children" value returned by the "GET /uri/$DIRCAP?t=json" operation
676 described above. In this format, each key is a child names, and the
677 corresponding value is a tuple of (type, childinfo). "type" is ignored, and
678 "childinfo" is a dictionary that contains "rw_uri", "ro_uri", and
679 "metadata" keys. You can take the output of "GET /uri/$DIRCAP1?t=json" and
680 use it as the input to "POST /uri/$DIRCAP2?t=set_children" to make DIR2
681 look very much like DIR1.
683 When the set_children request contains a child name that already exists in
684 the target directory, this command defaults to overwriting that child with
685 the new value (both child cap and metadata, but if the JSON data does not
686 contain a "metadata" key, the old child's metadata is preserved). The
687 command takes a boolean "overwrite=" query argument to control this
688 behavior. If you use "?t=set_children&overwrite=false", then an attempt to
689 replace an existing child will instead cause an error.
691 Any "tahoe" key in the new child's "metadata" value is ignored. Any
692 existing "tahoe" metadata is preserved. The metadata["tahoe"] value is
693 reserved for metadata generated by the tahoe node itself. The only two keys
694 currently placed here are "linkcrtime" and "linkmotime". For details, see
695 the section above entitled "Get Information About A File Or Directory (as
696 JSON)", in the "About the metadata" subsection.
699 === Deleting a File or Directory ===
701 DELETE /uri/$DIRCAP/[SUBDIRS../]CHILDNAME
703 This removes the given name from its parent directory. CHILDNAME is the
704 name to be removed, and $DIRCAP/SUBDIRS.. indicates the directory that will
707 Note that this does not actually delete the file or directory that the name
708 points to from the tahoe grid -- it only removes the named reference from
709 this directory. If there are other names in this directory or in other
710 directories that point to the resource, then it will remain accessible
711 through those paths. Even if all names pointing to this object are removed
712 from their parent directories, then someone with possession of its read-cap
713 can continue to access the object through that cap.
715 The object will only become completely unreachable once 1: there are no
716 reachable directories that reference it, and 2: nobody is holding a read-
717 or write- cap to the object. (This behavior is very similar to the way
718 hardlinks and anonymous files work in traditional unix filesystems).
720 This operation will not modify more than a single directory. Intermediate
721 directories which were implicitly created by PUT or POST methods will *not*
722 be automatically removed by DELETE.
724 This method returns the file- or directory- cap of the object that was just
727 == Browser Operations ==
729 This section describes the HTTP operations that provide support for humans
730 running a web browser. Most of these operations use HTML forms that use POST
731 to drive the Tahoe node. This section is intended for HTML authors who want
732 to write web pages that contain forms and buttons which manipulate the Tahoe
735 Note that for all POST operations, the arguments listed can be provided
736 either as URL query arguments or as form body fields. URL query arguments are
737 separated from the main URL by "?", and from each other by "&". For example,
738 "POST /uri/$DIRCAP?t=upload&mutable=true". Form body fields are usually
739 specified by using <input type="hidden"> elements. For clarity, the
740 descriptions below display the most significant arguments as URL query args.
742 === Viewing A Directory (as HTML) ===
744 GET /uri/$DIRCAP/[SUBDIRS../]
746 This returns an HTML page, intended to be displayed to a human by a web
747 browser, which contains HREF links to all files and directories reachable
748 from this directory. These HREF links do not have a t= argument, meaning
749 that a human who follows them will get pages also meant for a human. It also
750 contains forms to upload new files, and to delete files and directories.
751 Those forms use POST methods to do their job.
753 === Viewing/Downloading a File ===
756 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME
758 This will retrieve the contents of the given file. The HTTP response body
759 will contain the sequence of bytes that make up the file.
761 If you want the HTTP response to include a useful Content-Type header,
762 either use the second form (which starts with a $DIRCAP), or add a
763 "filename=foo" query argument, like "GET /uri/$FILECAP?filename=foo.jpg".
764 The bare "GET /uri/$FILECAP" does not give the Tahoe node enough information
765 to determine a Content-Type (since Tahoe immutable files are merely
766 sequences of bytes, not typed+named file objects).
768 If the URL has both filename= and "save=true" in the query arguments, then
769 the server to add a "Content-Disposition: attachment" header, along with a
770 filename= parameter. When a user clicks on such a link, most browsers will
771 offer to let the user save the file instead of displaying it inline (indeed,
772 most browsers will refuse to display it inline). "true", "t", "1", and other
773 case-insensitive equivalents are all treated the same.
775 Character-set handling in URLs and HTTP headers is a dubious art[1]. For
776 maximum compatibility, Tahoe simply copies the bytes from the filename=
777 argument into the Content-Disposition header's filename= parameter, without
778 trying to interpret them in any particular way.
781 GET /named/$FILECAP/FILENAME
783 This is an alternate download form which makes it easier to get the correct
784 filename. The Tahoe server will provide the contents of the given file, with
785 a Content-Type header derived from the given filename. This form is used to
786 get browsers to use the "Save Link As" feature correctly, and also helps
787 command-line tools like "wget" and "curl" use the right filename. Note that
788 this form can *only* be used with file caps; it is an error to use a
789 directory cap after the /named/ prefix.
791 === Get Information About A File Or Directory (as HTML) ===
793 GET /uri/$FILECAP?t=info
794 GET /uri/$DIRCAP/?t=info
795 GET /uri/$DIRCAP/[SUBDIRS../]SUBDIR/?t=info
796 GET /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=info
798 This returns a human-oriented HTML page with more detail about the selected
799 file or directory object. This page contains the following items:
804 raw contents (text/plain)
805 access caps (URIs): verify-cap, read-cap, write-cap (for mutable objects)
806 check/verify/repair form
807 deep-check/deep-size/deep-stats/manifest (for directories)
808 replace-conents form (for mutable files)
810 === Creating a Directory ===
814 This creates a new empty directory, but does not attach it to the virtual
817 If a "redirect_to_result=true" argument is provided, then the HTTP response
818 will cause the web browser to be redirected to a /uri/$DIRCAP page that
819 gives access to the newly-created directory. If you bookmark this page,
820 you'll be able to get back to the directory again in the future. This is the
821 recommended way to start working with a Tahoe server: create a new unlinked
822 directory (using redirect_to_result=true), then bookmark the resulting
823 /uri/$DIRCAP page. There is a "create directory" button on the Welcome page
824 to invoke this action.
826 If "redirect_to_result=true" is not provided (or is given a value of
827 "false"), then the HTTP response body will simply be the write-cap of the
830 POST /uri/$DIRCAP/[SUBDIRS../]?t=mkdir&name=CHILDNAME
832 This creates a new empty directory as a child of the designated SUBDIR. This
833 will create additional intermediate directories as necessary.
835 If a "when_done=URL" argument is provided, the HTTP response will cause the
836 web browser to redirect to the given URL. This provides a convenient way to
837 return the browser to the directory that was just modified. Without a
838 when_done= argument, the HTTP response will simply contain the write-cap of
839 the directory that was just created.
842 === Uploading a File ===
846 This uploads a file, and produces a file-cap for the contents, but does not
847 attach the file into the virtual drive. No directories will be modified by
850 The file must be provided as the "file" field of an HTML encoded form body,
851 produced in response to an HTML form like this:
852 <form action="/uri" method="POST" enctype="multipart/form-data">
853 <input type="hidden" name="t" value="upload" />
854 <input type="file" name="file" />
855 <input type="submit" value="Upload Unlinked" />
858 If a "when_done=URL" argument is provided, the response body will cause the
859 browser to redirect to the given URL. If the when_done= URL has the string
860 "%(uri)s" in it, that string will be replaced by a URL-escaped form of the
861 newly created file-cap. (Note that without this substitution, there is no
862 way to access the file that was just uploaded).
864 The default (in the absence of when_done=) is to return an HTML page that
865 describes the results of the upload. This page will contain information
866 about which storage servers were used for the upload, how long each
869 If a "mutable=true" argument is provided, the operation will create a
870 mutable file, and the response body will contain the write-cap instead of
871 the upload results page. The default is to create an immutable file,
872 returning the upload results page as a response.
875 POST /uri/$DIRCAP/[SUBDIRS../]?t=upload
877 This uploads a file, and attaches it as a new child of the given directory.
878 The file must be provided as the "file" field of an HTML encoded form body,
879 produced in response to an HTML form like this:
880 <form action="." method="POST" enctype="multipart/form-data">
881 <input type="hidden" name="t" value="upload" />
882 <input type="file" name="file" />
883 <input type="submit" value="Upload" />
886 A "name=" argument can be provided to specify the new child's name,
887 otherwise it will be taken from the "filename" field of the upload form
888 (most web browsers will copy the last component of the original file's
889 pathname into this field). To avoid confusion, name= is not allowed to
892 If there is already a child with that name, and it is a mutable file, then
893 its contents are replaced with the data being uploaded. If it is not a
894 mutable file, the default behavior is to remove the existing child before
895 creating a new one. To prevent this (and make the operation return an error
896 instead of overwriting the old child), add a "replace=false" argument, as
897 "?t=upload&replace=false". With replace=false, this operation will return an
898 HTTP 409 "Conflict" error if there is already an object at the given
899 location, rather than overwriting the existing object. Note that "true",
900 "t", and "1" are all synonyms for "True", and "false", "f", and "0" are
901 synonyms for "False". the parameter is case-insensitive.
903 This will create additional intermediate directories as necessary, although
904 since it is expected to be triggered by a form that was retrieved by "GET
905 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
908 If a "mutable=true" argument is provided, any new file that is created will
909 be a mutable file instead of an immutable one. <input type="checkbox"
910 name="mutable" /> will give the user a way to set this option.
912 If a "when_done=URL" argument is provided, the HTTP response will cause the
913 web browser to redirect to the given URL. This provides a convenient way to
914 return the browser to the directory that was just modified. Without a
915 when_done= argument, the HTTP response will simply contain the file-cap of
916 the file that was just uploaded (a write-cap for mutable files, or a
917 read-cap for immutable files).
919 POST /uri/$DIRCAP/[SUBDIRS../]FILENAME?t=upload
921 This also uploads a file and attaches it as a new child of the given
922 directory. It is a slight variant of the previous operation, as the URL
923 refers to the target file rather than the parent directory. It is otherwise
924 identical: this accepts mutable= and when_done= arguments too.
926 POST /uri/$FILECAP?t=upload
928 This modifies the contents of an existing mutable file in-place. An error is
929 signalled if $FILECAP does not refer to a mutable file. It behaves just like
930 the "PUT /uri/$FILECAP" form, but uses a POST for the benefit of HTML forms
933 === Attaching An Existing File Or Directory (by URI) ===
935 POST /uri/$DIRCAP/[SUBDIRS../]?t=uri&name=CHILDNAME&uri=CHILDCAP
937 This attaches a given read- or write- cap "CHILDCAP" to the designated
938 directory, with a specified child name. This behaves much like the PUT t=uri
939 operation, and is a lot like a UNIX hardlink.
941 This will create additional intermediate directories as necessary, although
942 since it is expected to be triggered by a form that was retrieved by "GET
943 /uri/$DIRCAP/[SUBDIRS../]", it is likely that the parent directory will
946 This accepts the same replace= argument as POST t=upload.
948 === Deleting A Child ===
950 POST /uri/$DIRCAP/[SUBDIRS../]?t=delete&name=CHILDNAME
952 This instructs the node to delete a child object (file or subdirectory) from
953 the given directory. Note that the entire subtree is removed. This is
954 somewhat like "rm -rf" (from the point of view of the parent), but other
955 references into the subtree will see that the child subdirectories are not
956 modified by this operation. Only the link from the given directory to its
959 === Renaming A Child ===
961 POST /uri/$DIRCAP/[SUBDIRS../]?t=rename&from_name=OLD&to_name=NEW
963 This instructs the node to rename a child of the given directory. This is
964 exactly the same as removing the child, then adding the same child-cap under
965 the new name. This operation cannot move the child to a different directory.
967 This operation will replace any existing child of the new name, making it
968 behave like the UNIX "mv -f" command.
970 === Other Utilities ===
974 This causes a redirect to /uri/$CAP, and retains any additional query
975 arguments (like filename= or save=). This is for the convenience of web
976 forms which allow the user to paste in a read- or write- cap (obtained
977 through some out-of-band channel, like IM or email).
979 Note that this form merely redirects to the specific file or directory
980 indicated by the $CAP: unlike the GET /uri/$DIRCAP form, you cannot
981 traverse to children by appending additional path segments to the URL.
983 GET /uri/$DIRCAP/[SUBDIRS../]?t=rename-form&name=$CHILDNAME
985 This provides a useful facility to browser-based user interfaces. It
986 returns a page containing a form targetting the "POST $DIRCAP t=rename"
987 functionality described above, with the provided $CHILDNAME present in the
988 'from_name' field of that form. I.e. this presents a form offering to
989 rename $CHILDNAME, requesting the new name, and submitting POST rename.
991 GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=uri
993 This returns the file- or directory- cap for the specified object.
995 GET /uri/$DIRCAP/[SUBDIRS../]CHILDNAME?t=readonly-uri
997 This returns a read-only file- or directory- cap for the specified object.
998 If the object is an immutable file, this will return the same value as
1001 === Debugging and Testing Features ===
1003 These URLs are less-likely to be helpful to the casual Tahoe user, and are
1004 mainly intended for developers.
1008 This triggers the FileChecker to determine the current "health" of the
1009 given file or directory, by counting how many shares are available. The
1010 page that is returned will display the results. This can be used as a "show
1011 me detailed information about this file" page.
1013 If a verify=true argument is provided, the node will perform a more
1014 intensive check, downloading and verifying every single bit of every share.
1016 If an add-lease=true argument is provided, the node will also add (or
1017 renew) a lease to every share it encounters. Each lease will keep the share
1018 alive for a certain period of time (one month by default). Once the last
1019 lease expires or is explicitly cancelled, the storage server is allowed to
1022 If an output=JSON argument is provided, the response will be
1023 machine-readable JSON instead of human-oriented HTML. The data is a
1024 dictionary with the following keys:
1026 storage-index: a base32-encoded string with the objects's storage index,
1027 or an empty string for LIT files
1028 summary: a string, with a one-line summary of the stats of the file
1029 results: a dictionary that describes the state of the file. For LIT files,
1030 this dictionary has only the 'healthy' key, which will always be
1031 True. For distributed files, this dictionary has the following
1033 count-shares-good: the number of good shares that were found
1034 count-shares-needed: 'k', the number of shares required for recovery
1035 count-shares-expected: 'N', the number of total shares generated
1036 count-good-share-hosts: the number of distinct storage servers with
1037 good shares. If this number is less than
1038 count-shares-good, then some shares are doubled
1039 up, increasing the correlation of failures. This
1040 indicates that one or more shares should be
1041 moved to an otherwise unused server, if one is
1043 count-wrong-shares: for mutable files, the number of shares for
1044 versions other than the 'best' one (highest
1045 sequence number, highest roothash). These are
1047 count-recoverable-versions: for mutable files, the number of
1048 recoverable versions of the file. For
1049 a healthy file, this will equal 1.
1050 count-unrecoverable-versions: for mutable files, the number of
1051 unrecoverable versions of the file.
1052 For a healthy file, this will be 0.
1053 count-corrupt-shares: the number of shares with integrity failures
1054 list-corrupt-shares: a list of "share locators", one for each share
1055 that was found to be corrupt. Each share locator
1056 is a list of (serverid, storage_index, sharenum).
1057 needs-rebalancing: (bool) True if there are multiple shares on a single
1058 storage server, indicating a reduction in reliability
1059 that could be resolved by moving shares to new
1061 servers-responding: list of base32-encoded storage server identifiers,
1062 one for each server which responded to the share
1064 healthy: (bool) True if the file is completely healthy, False otherwise.
1065 Healthy files have at least N good shares. Overlapping shares
1066 (indicated by count-good-share-hosts < count-shares-good) do not
1067 currently cause a file to be marked unhealthy. If there are at
1068 least N good shares, then corrupt shares do not cause the file to
1069 be marked unhealthy, although the corrupt shares will be listed
1070 in the results (list-corrupt-shares) and should be manually
1071 removed to wasting time in subsequent downloads (as the
1072 downloader rediscovers the corruption and uses alternate shares).
1073 sharemap: dict mapping share identifier to list of serverids
1074 (base32-encoded strings). This indicates which servers are
1075 holding which shares. For immutable files, the shareid is
1076 an integer (the share number, from 0 to N-1). For
1077 immutable files, it is a string of the form
1078 'seq%d-%s-sh%d', containing the sequence number, the
1079 roothash, and the share number.
1081 POST $URL?t=start-deep-check (must add &ophandle=XYZ)
1083 This initiates a recursive walk of all files and directories reachable from
1084 the target, performing a check on each one just like t=check. The result
1085 page will contain a summary of the results, including details on any
1086 file/directory that was not fully healthy.
1088 t=start-deep-check can only be invoked on a directory. An error (400
1089 BAD_REQUEST) will be signalled if it is invoked on a file. The recursive
1090 walker will deal with loops safely.
1092 This accepts the same verify= and add-lease= arguments as t=check.
1094 Since this operation can take a long time (perhaps a second per object),
1095 the ophandle= argument is required (see "Slow Operations, Progress, and
1096 Cancelling" above). The response to this POST will be a redirect to the
1097 corresponding /operations/$HANDLE page (with output=HTML or output=JSON to
1098 match the output= argument given to the POST). The deep-check operation
1099 will continue to run in the background, and the /operations page should be
1100 used to find out when the operation is done.
1102 Detailed check results for non-healthy files and directories will be
1103 available under /operations/$HANDLE/$STORAGEINDEX, and the HTML status will
1104 contain links to these detailed results.
1106 The HTML /operations/$HANDLE page for incomplete operations will contain a
1107 meta-refresh tag, set to 60 seconds, so that a browser which uses
1108 deep-check will automatically poll until the operation has completed.
1110 The JSON page (/options/$HANDLE?output=JSON) will contain a
1111 machine-readable JSON dictionary with the following keys:
1113 finished: a boolean, True if the operation is complete, else False. Some
1114 of the remaining keys may not be present until the operation
1116 root-storage-index: a base32-encoded string with the storage index of the
1117 starting point of the deep-check operation
1118 count-objects-checked: count of how many objects were checked. Note that
1119 non-distributed objects (i.e. small immutable LIT
1120 files) are not checked, since for these objects,
1121 the data is contained entirely in the URI.
1122 count-objects-healthy: how many of those objects were completely healthy
1123 count-objects-unhealthy: how many were damaged in some way
1124 count-corrupt-shares: how many shares were found to have corruption,
1125 summed over all objects examined
1126 list-corrupt-shares: a list of "share identifiers", one for each share
1127 that was found to be corrupt. Each share identifier
1128 is a list of (serverid, storage_index, sharenum).
1129 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1130 each file that was not fully healthy. 'pathname' is
1131 a list of strings (which can be joined by "/"
1132 characters to turn it into a single string),
1133 relative to the directory on which deep-check was
1134 invoked. The 'check-results' field is the same as
1135 that returned by t=check&output=JSON, described
1137 stats: a dictionary with the same keys as the t=start-deep-stats command
1140 POST $URL?t=stream-deep-check
1142 This initiates a recursive walk of all files and directories reachable from
1143 the target, performing a check on each one just like t=check. For each
1144 unique object (duplicates are skipped), a single line of JSON is emitted to
1145 the HTTP response channel (or an error indication, see below). When the walk
1146 is complete, a final line of JSON is emitted which contains the accumulated
1147 file-size/count "deep-stats" data.
1149 This command takes the same arguments as t=start-deep-check.
1151 A CLI tool can split the response stream on newlines into "response units",
1152 and parse each response unit as JSON. Each such parsed unit will be a
1153 dictionary, and will contain at least the "type" key: a string, one of
1154 "file", "directory", or "stats".
1156 For all units that have a type of "file" or "directory", the dictionary will
1157 contain the following keys:
1159 "path": a list of strings, with the path that is traversed to reach the
1161 "cap": a writecap for the file or directory, if available, else a readcap
1162 "verifycap": a verifycap for the file or directory
1163 "repaircap": the weakest cap which can still be used to repair the object
1164 "storage-index": a base32 storage index for the object
1165 "check-results": a copy of the dictionary which would be returned by
1166 t=check&output=json, with three top-level keys:
1167 "storage-index", "summary", and "results", and a variety
1168 of counts and sharemaps in the "results" value.
1170 Note that non-distributed files (i.e. LIT files) will have values of None
1171 for verifycap, repaircap, and storage-index, since these files can neither
1172 be verified nor repaired, and are not stored on the storage servers.
1173 Likewise the check-results dictionary will be limited: an empty string for
1174 storage-index, and a results dictionary with only the "healthy" key.
1176 The last unit in the stream will have a type of "stats", and will contain
1177 the keys described in the "start-deep-stats" operation, below.
1179 If any errors occur during the traversal (specifically if a directory is
1180 unrecoverable, such that further traversal is not possible), an error
1181 indication is written to the response body, instead of the usual line of
1182 JSON. This error indication line will begin with the string "ERROR:" (in all
1183 caps), and contain a summary of the error on the rest of the line. The
1184 remaining lines of the response body will be a python exception. The client
1185 application should look for the ERROR: and stop processing JSON as soon as
1186 it is seen. Note that neither a file being unrecoverable nor a directory
1187 merely being unhealthy will cause traversal to stop. The line just before
1188 the ERROR: will describe the directory that was untraversable, since the
1189 unit is emitted to the HTTP response body before the child is traversed.
1192 POST $URL?t=check&repair=true
1194 This performs a health check of the given file or directory, and if the
1195 checker determines that the object is not healthy (some shares are missing
1196 or corrupted), it will perform a "repair". During repair, any missing
1197 shares will be regenerated and uploaded to new servers.
1199 This accepts the same verify=true and add-lease= arguments as t=check. When
1200 an output=JSON argument is provided, the machine-readable JSON response
1201 will contain the following keys:
1203 storage-index: a base32-encoded string with the objects's storage index,
1204 or an empty string for LIT files
1205 repair-attempted: (bool) True if repair was attempted
1206 repair-successful: (bool) True if repair was attempted and the file was
1207 fully healthy afterwards. False if no repair was
1208 attempted, or if a repair attempt failed.
1209 pre-repair-results: a dictionary that describes the state of the file
1210 before any repair was performed. This contains exactly
1211 the same keys as the 'results' value of the t=check
1212 response, described above.
1213 post-repair-results: a dictionary that describes the state of the file
1214 after any repair was performed. If no repair was
1215 performed, post-repair-results and pre-repair-results
1216 will be the same. This contains exactly the same keys
1217 as the 'results' value of the t=check response,
1220 POST $URL?t=start-deep-check&repair=true (must add &ophandle=XYZ)
1222 This triggers a recursive walk of all files and directories, performing a
1223 t=check&repair=true on each one.
1225 Like t=start-deep-check without the repair= argument, this can only be
1226 invoked on a directory. An error (400 BAD_REQUEST) will be signalled if it
1227 is invoked on a file. The recursive walker will deal with loops safely.
1229 This accepts the same verify= and add-lease= arguments as
1230 t=start-deep-check. It uses the same ophandle= mechanism as
1231 start-deep-check. When an output=JSON argument is provided, the response
1232 will contain the following keys:
1234 finished: (bool) True if the operation has completed, else False
1235 root-storage-index: a base32-encoded string with the storage index of the
1236 starting point of the deep-check operation
1237 count-objects-checked: count of how many objects were checked
1239 count-objects-healthy-pre-repair: how many of those objects were completely
1240 healthy, before any repair
1241 count-objects-unhealthy-pre-repair: how many were damaged in some way
1242 count-objects-healthy-post-repair: how many of those objects were completely
1243 healthy, after any repair
1244 count-objects-unhealthy-post-repair: how many were damaged in some way
1246 count-repairs-attempted: repairs were attempted on this many objects.
1247 count-repairs-successful: how many repairs resulted in healthy objects
1248 count-repairs-unsuccessful: how many repairs resulted did not results in
1249 completely healthy objects
1250 count-corrupt-shares-pre-repair: how many shares were found to have
1251 corruption, summed over all objects
1252 examined, before any repair
1253 count-corrupt-shares-post-repair: how many shares were found to have
1254 corruption, summed over all objects
1255 examined, after any repair
1256 list-corrupt-shares: a list of "share identifiers", one for each share
1257 that was found to be corrupt (before any repair).
1258 Each share identifier is a list of (serverid,
1259 storage_index, sharenum).
1260 list-remaining-corrupt-shares: like list-corrupt-shares, but mutable shares
1261 that were successfully repaired are not
1262 included. These are shares that need
1263 manual processing. Since immutable shares
1264 cannot be modified by clients, all corruption
1265 in immutable shares will be listed here.
1266 list-unhealthy-files: a list of (pathname, check-results) tuples, for
1267 each file that was not fully healthy. 'pathname' is
1268 relative to the directory on which deep-check was
1269 invoked. The 'check-results' field is the same as
1270 that returned by t=check&repair=true&output=JSON,
1272 stats: a dictionary with the same keys as the t=start-deep-stats command
1275 POST $URL?t=stream-deep-check&repair=true
1277 This triggers a recursive walk of all files and directories, performing a
1278 t=check&repair=true on each one. For each unique object (duplicates are
1279 skipped), a single line of JSON is emitted to the HTTP response channel (or
1280 an error indication). When the walk is complete, a final line of JSON is
1281 emitted which contains the accumulated file-size/count "deep-stats" data.
1283 This emits the same data as t=stream-deep-check (without the repair=true),
1284 except that the "check-results" field is replaced with a
1285 "check-and-repair-results" field, which contains the keys returned by
1286 t=check&repair=true&output=json (i.e. repair-attempted, repair-successful,
1287 pre-repair-results, and post-repair-results). The output does not contain
1288 the summary dictionary that is provied by t=start-deep-check&repair=true
1289 (the one with count-objects-checked and list-unhealthy-files), since the
1290 receiving client is expected to calculate those values itself from the
1291 stream of per-object check-and-repair-results.
1293 Note that the "ERROR:" indication will only be emitted if traversal stops,
1294 which will only occur if an unrecoverable directory is encountered. If a
1295 file or directory repair fails, the traversal will continue, and the repair
1296 failure will be indicated in the JSON data (in the "repair-successful" key).
1298 POST $DIRURL?t=start-manifest (must add &ophandle=XYZ)
1300 This operation generates a "manfest" of the given directory tree, mostly
1301 for debugging. This is a table of (path, filecap/dircap), for every object
1302 reachable from the starting directory. The path will be slash-joined, and
1303 the filecap/dircap will contain a link to the object in question. This page
1304 gives immediate access to every object in the virtual filesystem subtree.
1306 This operation uses the same ophandle= mechanism as deep-check. The
1307 corresponding /operations/$HANDLE page has three different forms. The
1308 default is output=HTML.
1310 If output=text is added to the query args, the results will be a text/plain
1311 list. The first line is special: it is either "finished: yes" or "finished:
1312 no"; if the operation is not finished, you must periodically reload the
1313 page until it completes. The rest of the results are a plaintext list, with
1314 one file/dir per line, slash-separated, with the filecap/dircap separated
1317 If output=JSON is added to the queryargs, then the results will be a
1318 JSON-formatted dictionary with six keys. Note that because large directory
1319 structures can result in very large JSON results, the full results will not
1320 be available until the operation is complete (i.e. until output["finished"]
1323 finished (bool): if False then you must reload the page until True
1324 origin_si (base32 str): the storage index of the starting point
1325 manifest: list of (path, cap) tuples, where path is a list of strings.
1326 verifycaps: list of (printable) verify cap strings
1327 storage-index: list of (base32) storage index strings
1328 stats: a dictionary with the same keys as the t=start-deep-stats command
1331 POST $DIRURL?t=start-deep-size (must add &ophandle=XYZ)
1333 This operation generates a number (in bytes) containing the sum of the
1334 filesize of all directories and immutable files reachable from the given
1335 directory. This is a rough lower bound of the total space consumed by this
1336 subtree. It does not include space consumed by mutable files, nor does it
1337 take expansion or encoding overhead into account. Later versions of the
1338 code may improve this estimate upwards.
1340 The /operations/$HANDLE status output consists of two lines of text:
1345 POST $DIRURL?t=start-deep-stats (must add &ophandle=XYZ)
1347 This operation performs a recursive walk of all files and directories
1348 reachable from the given directory, and generates a collection of
1349 statistics about those objects.
1351 The result (obtained from the /operations/$OPHANDLE page) is a
1352 JSON-serialized dictionary with the following keys (note that some of these
1353 keys may be missing until 'finished' is True):
1355 finished: (bool) True if the operation has finished, else False
1356 count-immutable-files: count of how many CHK files are in the set
1357 count-mutable-files: same, for mutable files (does not include directories)
1358 count-literal-files: same, for LIT files (data contained inside the URI)
1359 count-files: sum of the above three
1360 count-directories: count of directories
1361 count-unknown: count of unrecognized objects (perhaps from the future)
1362 size-immutable-files: total bytes for all CHK files in the set, =deep-size
1363 size-mutable-files (TODO): same, for current version of all mutable files
1364 size-literal-files: same, for LIT files
1365 size-directories: size of directories (includes size-literal-files)
1366 size-files-histogram: list of (minsize, maxsize, count) buckets,
1367 with a histogram of filesizes, 5dB/bucket,
1368 for both literal and immutable files
1369 largest-directory: number of children in the largest directory
1370 largest-immutable-file: number of bytes in the largest CHK file
1372 size-mutable-files is not implemented, because it would require extra
1373 queries to each mutable file to get their size. This may be implemented in
1376 Assuming no sharing, the basic space consumed by a single root directory is
1377 the sum of size-immutable-files, size-mutable-files, and size-directories.
1378 The actual disk space used by the shares is larger, because of the
1379 following sources of overhead:
1382 expansion due to erasure coding
1383 share management data (leases)
1384 backend (ext3) minimum block size
1386 POST $URL?t=stream-manifest
1388 This operation performs a recursive walk of all files and directories
1389 reachable from the given starting point. For each such unique object
1390 (duplicates are skipped), a single line of JSON is emitted to the HTTP
1391 response channel (or an error indication, see below). When the walk is
1392 complete, a final line of JSON is emitted which contains the accumulated
1393 file-size/count "deep-stats" data.
1395 A CLI tool can split the response stream on newlines into "response units",
1396 and parse each response unit as JSON. Each such parsed unit will be a
1397 dictionary, and will contain at least the "type" key: a string, one of
1398 "file", "directory", or "stats".
1400 For all units that have a type of "file" or "directory", the dictionary will
1401 contain the following keys:
1403 "path": a list of strings, with the path that is traversed to reach the
1405 "cap": a writecap for the file or directory, if available, else a readcap
1406 "verifycap": a verifycap for the file or directory
1407 "repaircap": the weakest cap which can still be used to repair the object
1408 "storage-index": a base32 storage index for the object
1410 Note that non-distributed files (i.e. LIT files) will have values of None
1411 for verifycap, repaircap, and storage-index, since these files can neither
1412 be verified nor repaired, and are not stored on the storage servers.
1414 The last unit in the stream will have a type of "stats", and will contain
1415 the keys described in the "start-deep-stats" operation, below.
1417 If any errors occur during the traversal (specifically if a directory is
1418 unrecoverable, such that further traversal is not possible), an error
1419 indication is written to the response body, instead of the usual line of
1420 JSON. This error indication line will begin with the string "ERROR:" (in all
1421 caps), and contain a summary of the error on the rest of the line. The
1422 remaining lines of the response body will be a python exception. The client
1423 application should look for the ERROR: and stop processing JSON as soon as
1424 it is seen. The line just before the ERROR: will describe the directory that
1425 was untraversable, since the manifest entry is emitted to the HTTP response
1426 body before the child is traversed.
1428 == Other Useful Pages ==
1430 The portion of the web namespace that begins with "/uri" (and "/named") is
1431 dedicated to giving users (both humans and programs) access to the Tahoe
1432 virtual filesystem. The rest of the namespace provides status information
1433 about the state of the Tahoe node.
1435 GET / (the root page)
1437 This is the "Welcome Page", and contains a few distinct sections:
1439 Node information: library versions, local nodeid, services being provided.
1441 Filesystem Access Forms: create a new directory, view a file/directory by
1442 URI, upload a file (unlinked), download a file by
1445 Grid Status: introducer information, helper information, connected storage
1450 This page lists all active uploads and downloads, and contains a short list
1451 of recent upload/download operations. Each operation has a link to a page
1452 that describes file sizes, servers that were involved, and the time consumed
1453 in each phase of the operation.
1455 A GET of /status/?t=json will contain a machine-readable subset of the same
1456 data. It returns a JSON-encoded dictionary. The only key defined at this
1457 time is "active", with a value that is a list of operation dictionaries, one
1458 for each active operation. Once an operation is completed, it will no longer
1459 appear in data["active"] .
1461 Each op-dict contains a "type" key, one of "upload", "download",
1462 "mapupdate", "publish", or "retrieve" (the first two are for immutable
1463 files, while the latter three are for mutable files and directories).
1465 The "upload" op-dict will contain the following keys:
1467 type (string): "upload"
1468 storage-index-string (string): a base32-encoded storage index
1469 total-size (int): total size of the file
1470 status (string): current status of the operation
1471 progress-hash (float): 1.0 when the file has been hashed
1472 progress-ciphertext (float): 1.0 when the file has been encrypted.
1473 progress-encode-push (float): 1.0 when the file has been encoded and
1474 pushed to the storage servers. For helper
1475 uploads, the ciphertext value climbs to 1.0
1476 first, then encoding starts. For unassisted
1477 uploads, ciphertext and encode-push progress
1478 will climb at the same pace.
1480 The "download" op-dict will contain the following keys:
1482 type (string): "download"
1483 storage-index-string (string): a base32-encoded storage index
1484 total-size (int): total size of the file
1485 status (string): current status of the operation
1486 progress (float): 1.0 when the file has been fully downloaded
1488 Front-ends which want to report progress information are advised to simply
1489 average together all the progress-* indicators. A slightly more accurate
1490 value can be found by ignoring the progress-hash value (since the current
1491 implementation hashes synchronously, so clients will probably never see
1492 progress-hash!=1.0).
1496 This page provides a basic tool to predict the likely storage and bandwidth
1497 requirements of a large Tahoe grid. It provides forms to input things like
1498 total number of users, number of files per user, average file size, number
1499 of servers, expansion ratio, hard drive failure rate, etc. It then provides
1500 numbers like how many disks per server will be needed, how many read
1501 operations per second should be expected, and the likely MTBF for files in
1502 the grid. This information is very preliminary, and the model upon which it
1503 is based still needs a lot of work.
1507 If the node is running a helper (i.e. if [helper]enabled is set to True in
1508 tahoe.cfg), then this page will provide a list of all the helper operations
1509 currently in progress. If "?t=json" is added to the URL, it will return a
1510 JSON-formatted list of helper statistics, which can then be used to produce
1511 graphs to indicate how busy the helper is.
1515 This page provides "node statistics", which are collected from a variety of
1518 load_monitor: every second, the node schedules a timer for one second in
1519 the future, then measures how late the subsequent callback
1520 is. The "load_average" is this tardiness, measured in
1521 seconds, averaged over the last minute. It is an indication
1522 of a busy node, one which is doing more work than can be
1523 completed in a timely fashion. The "max_load" value is the
1524 highest value that has been seen in the last 60 seconds.
1526 cpu_monitor: every minute, the node uses time.clock() to measure how much
1527 CPU time it has used, and it uses this value to produce
1528 1min/5min/15min moving averages. These values range from 0%
1529 (0.0) to 100% (1.0), and indicate what fraction of the CPU
1530 has been used by the Tahoe node. Not all operating systems
1531 provide meaningful data to time.clock(): they may report 100%
1532 CPU usage at all times.
1534 uploader: this counts how many immutable files (and bytes) have been
1535 uploaded since the node was started
1537 downloader: this counts how many immutable files have been downloaded
1538 since the node was started
1540 publishes: this counts how many mutable files (including directories) have
1541 been modified since the node was started
1543 retrieves: this counts how many mutable files (including directories) have
1544 been read since the node was started
1546 There are other statistics that are tracked by the node. The "raw stats"
1547 section shows a formatted dump of all of them.
1549 By adding "?t=json" to the URL, the node will return a JSON-formatted
1550 dictionary of stats values, which can be used by other tools to produce
1551 graphs of node behavior. The misc/munin/ directory in the source
1552 distribution provides some tools to produce these graphs.
1554 GET / (introducer status)
1556 For Introducer nodes, the welcome page displays information about both
1557 clients and servers which are connected to the introducer. Servers make
1558 "service announcements", and these are listed in a table. Clients will
1559 subscribe to hear about service announcements, and these subscriptions are
1560 listed in a separate table. Both tables contain information about what
1561 version of Tahoe is being run by the remote node, their advertised and
1562 outbound IP addresses, their nodeid and nickname, and how long they have
1565 By adding "?t=json" to the URL, the node will return a JSON-formatted
1566 dictionary of stats values, which can be used to produce graphs of connected
1567 clients over time. This dictionary has the following keys:
1569 ["subscription_summary"] : a dictionary mapping service name (like
1570 "storage") to an integer with the number of
1571 clients that have subscribed to hear about that
1573 ["announcement_summary"] : a dictionary mapping service name to an integer
1574 with the number of servers which are announcing
1576 ["announcement_distinct_hosts"] : a dictionary mapping service name to an
1577 integer which represents the number of
1578 distinct hosts that are providing that
1579 service. If two servers have announced
1580 FURLs which use the same hostnames (but
1581 different ports and tubids), they are
1582 considered to be on the same host.
1585 == Static Files in /public_html ==
1587 The wapi server will take any request for a URL that starts with /static
1588 and serve it from a configurable directory which defaults to
1589 $BASEDIR/public_html . This is configured by setting the "[node]web.static"
1590 value in $BASEDIR/tahoe.cfg . If this is left at the default value of
1591 "public_html", then http://localhost:3456/static/subdir/foo.html will be
1592 served with the contents of the file $BASEDIR/public_html/subdir/foo.html .
1594 This can be useful to serve a javascript application which provides a
1595 prettier front-end to the rest of the Tahoe wapi.
1598 == safety and security issues -- names vs. URIs ==
1600 Summary: use explicit file- and dir- caps whenever possible, to reduce the
1601 potential for surprises when the filesystem structure is changed.
1603 Tahoe provides a mutable filesystem, but the ways that the filesystem can
1604 change are limited. The only thing that can change is that the mapping from
1605 child names to child objects that each directory contains can be changed by
1606 adding a new child name pointing to an object, removing an existing child name,
1607 or changing an existing child name to point to a different object.
1609 Obviously if you query Tahoe for information about the filesystem and then act
1610 to change the filesystem (such as by getting a listing of the contents of a
1611 directory and then adding a file to the directory), then the filesystem might
1612 have been changed after you queried it and before you acted upon it. However,
1613 if you use the URI instead of the pathname of an object when you act upon the
1614 object, then the only change that can happen is if the object is a directory
1615 then the set of child names it has might be different. If, on the other hand,
1616 you act upon the object using its pathname, then a different object might be in
1617 that place, which can result in more kinds of surprises.
1619 For example, suppose you are writing code which recursively downloads the
1620 contents of a directory. The first thing your code does is fetch the listing
1621 of the contents of the directory. For each child that it fetched, if that
1622 child is a file then it downloads the file, and if that child is a directory
1623 then it recurses into that directory. Now, if the download and the recurse
1624 actions are performed using the child's name, then the results might be
1625 wrong, because for example a child name that pointed to a sub-directory when
1626 you listed the directory might have been changed to point to a file (in which
1627 case your attempt to recurse into it would result in an error and the file
1628 would be skipped), or a child name that pointed to a file when you listed the
1629 directory might now point to a sub-directory (in which case your attempt to
1630 download the child would result in a file containing HTML text describing the
1633 If your recursive algorithm uses the uri of the child instead of the name of
1634 the child, then those kinds of mistakes just can't happen. Note that both the
1635 child's name and the child's URI are included in the results of listing the
1636 parent directory, so it isn't any harder to use the URI for this purpose.
1638 In general, use names if you want "whatever object (whether file or
1639 directory) is found by following this name (or sequence of names) when my
1640 request reaches the server". Use URIs if you want "this particular object".
1642 == Concurrency Issues ==
1644 Tahoe uses both mutable and immutable files. Mutable files can be created
1645 explicitly by doing an upload with ?mutable=true added, or implicitly by
1646 creating a new directory (since a directory is just a special way to
1647 interpret a given mutable file).
1649 Mutable files suffer from the same consistency-vs-availability tradeoff that
1650 all distributed data storage systems face. It is not possible to
1651 simultaneously achieve perfect consistency and perfect availability in the
1652 face of network partitions (servers being unreachable or faulty).
1654 Tahoe tries to achieve a reasonable compromise, but there is a basic rule in
1655 place, known as the Prime Coordination Directive: "Don't Do That". What this
1656 means is that if write-access to a mutable file is available to several
1657 parties, then those parties are responsible for coordinating their activities
1658 to avoid multiple simultaneous updates. This could be achieved by having
1659 these parties talk to each other and using some sort of locking mechanism, or
1660 by serializing all changes through a single writer.
1662 The consequences of performing uncoordinated writes can vary. Some of the
1663 writers may lose their changes, as somebody else wins the race condition. In
1664 many cases the file will be left in an "unhealthy" state, meaning that there
1665 are not as many redundant shares as we would like (reducing the reliability
1666 of the file against server failures). In the worst case, the file can be left
1667 in such an unhealthy state that no version is recoverable, even the old ones.
1668 It is this small possibility of data loss that prompts us to issue the Prime
1669 Coordination Directive.
1671 Tahoe nodes implement internal serialization to make sure that a single Tahoe
1672 node cannot conflict with itself. For example, it is safe to issue two
1673 directory modification requests to a single tahoe node's wapi server at the
1674 same time, because the Tahoe node will internally delay one of them until
1675 after the other has finished being applied. (This feature was introduced in
1676 Tahoe-1.1; back with Tahoe-1.0 the web client was responsible for serializing
1677 web requests themselves).
1679 For more details, please see the "Consistency vs Availability" and "The Prime
1680 Coordination Directive" sections of mutable.txt, in the same directory as
1684 [1]: URLs and HTTP and UTF-8, Oh My
1686 HTTP does not provide a mechanism to specify the character set used to
1687 encode non-ascii names in URLs (rfc2396#2.1). We prefer the convention that
1688 the filename= argument shall be a URL-encoded UTF-8 encoded unicode object.
1689 For example, suppose we want to provoke the server into using a filename of
1690 "f i a n c e-acute e" (i.e. F I A N C U+00E9 E). The UTF-8 encoding of this
1691 is 0x66 0x69 0x61 0x6e 0x63 0xc3 0xa9 0x65 (or "fianc\xC3\xA9e", as python's
1692 repr() function would show). To encode this into a URL, the non-printable
1693 characters must be escaped with the urlencode '%XX' mechansim, giving us
1694 "fianc%C3%A9e". Thus, the first line of the HTTP request will be "GET
1695 /uri/CAP...?save=true&filename=fianc%C3%A9e HTTP/1.1". Not all browsers
1696 provide this: IE7 uses the Latin-1 encoding, which is fianc%E9e.
1698 The response header will need to indicate a non-ASCII filename. The actual
1699 mechanism to do this is not clear. For ASCII filenames, the response header
1702 Content-Disposition: attachment; filename="english.txt"
1704 If Tahoe were to enforce the utf-8 convention, it would need to decode the
1705 URL argument into a unicode string, and then encode it back into a sequence
1706 of bytes when creating the response header. One possibility would be to use
1707 unencoded utf-8. Developers suggest that IE7 might accept this:
1709 #1: Content-Disposition: attachment; filename="fianc\xC3\xA9e"
1710 (note, the last four bytes of that line, not including the newline, are
1711 0xC3 0xA9 0x65 0x22)
1713 RFC2231#4 (dated 1997): suggests that the following might work, and some
1714 developers (http://markmail.org/message/dsjyokgl7hv64ig3) have reported that
1715 it is supported by firefox (but not IE7):
1717 #2: Content-Disposition: attachment; filename*=utf-8''fianc%C3%A9e
1719 My reading of RFC2616#19.5.1 (which defines Content-Disposition) says that
1720 the filename= parameter is defined to be wrapped in quotes (presumeably to
1721 allow spaces without breaking the parsing of subsequent parameters), which
1724 #3: Content-Disposition: attachment; filename*=utf-8''"fianc%C3%A9e"
1726 However this is contrary to the examples in the email thread listed above.
1728 Developers report that IE7 (when it is configured for UTF-8 URL encoding,
1729 which is not the default in asian countries), will accept:
1731 #4: Content-Disposition: attachment; filename=fianc%C3%A9e
1733 However, for maximum compatibility, Tahoe simply copies bytes from the URL
1734 into the response header, rather than enforcing the utf-8 convention. This
1735 means it does not try to decode the filename from the URL argument, nor does
1736 it encode the filename into the response header.
projects / tahoe-lafs / tahoe-lafs.git / blob