1 Pithos v2 Developer Guide
2 =========================
7 Pithos is a storage service implemented by GRNET (http://www.grnet.gr). Data is stored as objects, organized in containers, belonging to an account. This hierarchy of storage layers has been inspired by the OpenStack Object Storage (OOS) API and similar CloudFiles API by Rackspace. The Pithos API follows the OOS API as closely as possible. One of the design requirements has been to be able to use Pithos with clients built for the OOS, without changes.
9 However, to be able to take full advantage of the Pithos infrastructure, client software should be aware of the extensions that differentiate Pithos from OOS. Pithos objects can be updated, or appended to. Automatic version management, allows taking account and container listings back in time, as well as reading previous instances of objects.
11 The storage backend of Pithos is block oriented, permitting efficient, deduplicated data placement. The block structure of objects is exposed at the API layer, in order to encourage external software to implement advanced data management operations.
13 This document's goals are:
15 * Define the Pithos ReST API that allows the storage and retrieval of data and metadata via HTTP calls
16 * Specify metadata semantics and user interface guidelines for a common experience across client software implementations
18 The present document is meant to be read alongside the OOS API documentation. Thus, it is suggested that the reader is familiar with associated technologies, the OOS API as well as the first version of the Pithos API. This document refers to the second version of Pithos. Information on the first version of the storage API can be found at http://code.google.com/p/gss.
20 Whatever marked as to be determined (**TBD**), should not be considered by implementors.
25 ========================= ================================
27 ========================= ================================
28 0.4 (June 22, 2011) Support updating/deleting individual metadata with ``POST``.
29 0.3 (June 14, 2011) Large object support with ``X-Object-Manifest``.
30 \ Allow for publicly available objects via ``https://hostname/public``.
31 \ Support time-variant account/container listings.
32 \ Add source version when duplicating with PUT/COPY.
33 \ Request version in object HEAD/GET requests (list versions with GET).
34 0.2 (May 31, 2011) Add object meta listing and filtering in containers.
35 \ Include underlying storage characteristics in container meta.
36 \ Support for partial object updates through POST.
37 \ Expose object hashmaps through GET.
38 \ Support for multi-range object GET requests.
39 0.1 (May 17, 2011) Initial release. Based on OpenStack Object Storage Developer Guide API v1 (Apr. 15, 2011).
40 ========================= ================================
45 The URI requests supported by the Pithos API follow one of the following forms:
47 * Top level: ``https://hostname/v1/``
48 * Account level: ``https://hostname/v1/<account>``
49 * Container level: ``https://hostname/v1/<account>/<container>``
50 * Object level: ``https://hostname/v1/<account>/<container>/<object>``
52 All requests must include an ``X-Auth-Token``. The process of obtaining the token is still to be determined (**TBD**).
54 The allowable request operations and respective return codes per level are presented in the remainder of this chapter. Common to all requests are the following return codes.
56 ========================= ================================
57 Return Code Description
58 ========================= ================================
59 400 (Bad Request) The request is invalid
60 401 (Unauthorized) Request not allowed
61 404 (Not Found) The requested resource was not found
62 503 (Service Unavailable) The request cannot be completed because of an internal error
63 ========================= ================================
70 ========= ==================
72 ========= ==================
73 GET Authentication. This is kept for compatibility with the OOS API
74 ========= ==================
79 If the ``X-Auth-User`` and ``X-Auth-Key`` headers are given, a dummy ``X-Auth-Token`` and ``X-Storage-Url`` will be replied, which can be used as a guest token/namespace for testing Pithos.
81 ================ =====================
82 Return Code Description
83 ================ =====================
84 204 (No Content) The request succeeded
85 ================ =====================
93 ========= ==================
95 ========= ==================
96 HEAD Retrieve account metadata
98 POST Update account metadata
99 ========= ==================
104 ====================== ===================================
105 Request Parameter Name Value
106 ====================== ===================================
107 until Optional timestamp
108 ====================== ===================================
112 ========================== =====================
113 Reply Header Name Value
114 ========================== =====================
115 X-Account-Container-Count The total number of containers
116 X-Account-Object-Count The total number of objects (**TBD**)
117 X-Account-Bytes-Used The total number of bytes stored
118 X-Account-Bytes-Remaining The total number of bytes remaining (**TBD**)
119 X-Account-Last-Login The last login (**TBD**)
120 X-Account-Until-Timestamp The last account modification date until the timestamp provided
121 X-Account-Meta-* Optional user defined metadata
122 Last-Modified The last account modification date (regardless of ``until``)
123 ========================== =====================
127 ================ =====================
128 Return Code Description
129 ================ =====================
130 204 (No Content) The request succeeded
131 ================ =====================
137 ==================== ===========================
138 Request Header Name Value
139 ==================== ===========================
140 If-Modified-Since Retrieve if account has changed since provided timestamp
141 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
142 ==================== ===========================
146 ====================== =========================
147 Request Parameter Name Value
148 ====================== =========================
149 limit The amount of results requested (default is 10000)
150 marker Return containers with name lexicographically after marker
151 format Optional extended reply type (can be ``json`` or ``xml``)
152 until Optional timestamp
153 ====================== =========================
155 The reply is a list of container names. Account headers (as in a ``HEAD`` request) will also be included.
156 If a ``format=xml`` or ``format=json`` argument is given, extended information on the containers will be returned, serialized in the chosen format.
157 For each container, the information will include all container metadata (names will be in lower case and with hyphens replaced with underscores):
159 =========================== ============================
161 =========================== ============================
162 name The name of the container
163 count The number of objects inside the container
164 bytes The total size of the objects inside the container
165 last_modified The last container modification date (regardless of ``until``)
166 x_container_until_timestamp The last container modification date until the timestamp provided
167 x_container_meta_* Optional user defined metadata
168 =========================== ============================
170 For examples of container details returned in JSON/XML formats refer to the OOS API documentation.
172 =========================== =====================
173 Return Code Description
174 =========================== =====================
175 200 (OK) The request succeeded
176 204 (No Content) The account has no containers (only for non-extended replies)
177 304 (Not Modified) The account has not been modified
178 412 (Precondition Failed) The condition set can not be satisfied
179 =========================== =====================
181 Will use a ``200`` return code if the reply is of type json/xml.
187 ====================== ============================================
188 Request Parameter Name Value
189 ====================== ============================================
190 update Do not replace metadata (no value parameter)
191 ====================== ============================================
195 ==================== ===========================
196 Request Header Name Value
197 ==================== ===========================
198 X-Account-Meta-* Optional user defined metadata
199 ==================== ===========================
201 No reply content/headers.
203 The operation will overwrite all user defined metadata, except if ``update`` is defined.
205 ================ ===============================
206 Return Code Description
207 ================ ===============================
208 202 (Accepted) The request has been accepted
209 ================ ===============================
217 ========= ============================
218 Operation Description
219 ========= ============================
220 HEAD Retrieve container metadata
222 PUT Create/update container
223 POST Update container metadata
224 DELETE Delete container
225 ========= ============================
231 ====================== ===================================
232 Request Parameter Name Value
233 ====================== ===================================
234 until Optional timestamp
235 ====================== ===================================
239 =========================== ===============================
240 Reply Header Name Value
241 =========================== ===============================
242 X-Container-Object-Count The total number of objects in the container
243 X-Container-Bytes-Used The total number of bytes of all objects stored
244 X-Container-Block-Size The block size used by the storage backend
245 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
246 X-Container-Until-Timestamp The last container modification date until the timestamp provided
247 X-Container-Object-Meta A list with all meta keys used by objects
248 X-Container-Meta-* Optional user defined metadata
249 Last-Modified The last container modification date (regardless of ``until``)
250 =========================== ===============================
252 The keys returned in ``X-Container-Object-Meta`` are all the unique strings after the ``X-Object-Meta-`` prefix.
254 ================ ===============================
255 Return Code Description
256 ================ ===============================
257 204 (No Content) The request succeeded
258 ================ ===============================
264 ==================== ===========================
265 Request Header Name Value
266 ==================== ===========================
267 If-Modified-Since Retrieve if container has changed since provided timestamp
268 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
269 ==================== ===========================
273 ====================== ===================================
274 Request Parameter Name Value
275 ====================== ===================================
276 limit The amount of results requested (default is 10000)
277 marker Return containers with name lexicographically after marker
278 prefix Return objects starting with prefix
279 delimiter Return objects up to the delimiter (discussion follows)
280 path Assume ``prefix=path`` and ``delimiter=/``
281 format Optional extended reply type (can be ``json`` or ``xml``)
282 meta Return objects having the specified meta keys (can be a comma separated list)
283 until Optional timestamp
284 ====================== ===================================
286 The ``path`` parameter overrides ``prefix`` and ``delimiter``. When using ``path``, results will include objects ending in ``delimiter``.
288 The keys given with ``meta`` will be matched with the strings after the ``X-Object-Meta-`` prefix.
290 The reply is a list of object names. Container headers (as in a ``HEAD`` request) will also be included.
291 If a ``format=xml`` or ``format=json`` argument is given, extended information on the objects will be returned, serialized in the chosen format.
292 For each object, the information will include all object metadata (names will be in lower case and with hyphens replaced with underscores):
294 ========================== ======================================
296 ========================== ======================================
297 name The name of the object
298 hash The ETag of the object
299 bytes The size of the object
300 content_type The MIME content type of the object
301 content_encoding The encoding of the object (optional)
302 content-disposition The presentation style of the object (optional)
303 last_modified The last object modification date (regardless of version)
304 x_object_version The object's version identifier
305 x_object_version_timestamp The object's version timestamp
306 x_object_modified_by The user that committed the object's version
307 x_object_manifest Object parts prefix in ``<container>/<object>`` form (optional)
308 x_object_public Object is publicly accessible (optional) (**TBD**)
309 x_object_meta_* Optional user defined metadata
310 ========================== ======================================
312 Extended replies may also include virtual directory markers in separate sections of the ``json`` or ``xml`` results.
313 Virtual directory markers are only included when ``delimiter`` is explicitly set. They correspond to the substrings up to and including the first occurrence of the delimiter.
314 In JSON results they appear as dictionaries with only a ``"subdir"`` key. In XML results they appear interleaved with ``<object>`` tags as ``<subdir name="..." />``.
315 In case there is an object with the same name as a virtual directory marker, the object will be returned.
317 For examples of object details returned in JSON/XML formats refer to the OOS API documentation.
319 =========================== ===============================
320 Return Code Description
321 =========================== ===============================
322 200 (OK) The request succeeded
323 204 (No Content) The account has no containers (only for non-extended replies)
324 304 (Not Modified) The container has not been modified
325 412 (Precondition Failed) The condition set can not be satisfied
326 =========================== ===============================
328 Will use a ``200`` return code if the reply is of type json/xml.
334 ==================== ================================
335 Request Header Name Value
336 ==================== ================================
337 X-Container-Meta-* Optional user defined metadata
338 ==================== ================================
340 No reply content/headers.
342 ================ ===============================
343 Return Code Description
344 ================ ===============================
345 201 (Created) The container has been created
346 202 (Accepted) The request has been accepted
347 ================ ===============================
353 ====================== ============================================
354 Request Parameter Name Value
355 ====================== ============================================
356 update Do not replace metadata (no value parameter)
357 ====================== ============================================
361 ==================== ================================
362 Request Header Name Value
363 ==================== ================================
364 X-Container-Meta-* Optional user defined metadata
365 ==================== ================================
367 No reply content/headers.
369 The operation will overwrite all user defined metadata, except if ``update`` is defined.
371 ================ ===============================
372 Return Code Description
373 ================ ===============================
374 202 (Accepted) The request has been accepted
375 ================ ===============================
381 No request parameters/headers.
383 No reply content/headers.
385 ================ ===============================
386 Return Code Description
387 ================ ===============================
388 204 (No Content) The request succeeded
389 409 (Conflict) The container is not empty
390 ================ ===============================
398 ========= =================================
399 Operation Description
400 ========= =================================
401 HEAD Retrieve object metadata
403 PUT Write object data or copy/move object
406 POST Update object metadata/data
408 ========= =================================
414 ====================== ===================================
415 Request Parameter Name Value
416 ====================== ===================================
417 version Optional version identifier
418 ====================== ===================================
422 ========================== ===============================
423 Reply Header Name Value
424 ========================== ===============================
425 ETag The ETag of the object
426 Content-Length The size of the object
427 Content-Type The MIME content type of the object
428 Last-Modified The last object modification date (regardless of version)
429 Content-Encoding The encoding of the object (optional)
430 Content-Disposition The presentation style of the object (optional)
431 X-Object-Version The object's version identifier
432 X-Object-Version-Timestamp The object's version timestamp
433 X-Object-Modified-By The user that comitted the object's version
434 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
435 X-Object-Public Object is publicly accessible (optional) (**TBD**)
436 X-Object-Meta-* Optional user defined metadata
437 ========================== ===============================
441 ================ ===============================
442 Return Code Description
443 ================ ===============================
444 200 (No Content) The request succeeded
445 ================ ===============================
451 ==================== ================================
452 Request Header Name Value
453 ==================== ================================
454 Range Optional range of data to retrieve
455 If-Match Retrieve if ETags match
456 If-None-Match Retrieve if ETags don't match
457 If-Modified-Since Retrieve if object has changed since provided timestamp
458 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
459 ==================== ================================
463 ====================== ===================================
464 Request Parameter Name Value
465 ====================== ===================================
466 format Optional extended reply type (can be ``json`` or ``xml``)
467 version Optional version identifier or ``list`` (specify a format if requesting a list)
468 ====================== ===================================
470 The reply is the object's data (or part of it), except if a hashmap is requested with the ``format`` parameter, or a version list with ``version=list`` (in which case an extended reply format must be specified). Object headers (as in a ``HEAD`` request) are always included.
472 Hashmaps expose the underlying storage format of the object. Note that each hash is computed after trimming trailing null bytes of the corresponding block.
474 Example ``format=json`` reply:
478 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
480 Example ``format=xml`` reply:
484 <?xml version="1.0" encoding="UTF-8"?>
485 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
486 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
490 Version lists include the version identifier and timestamp for each available object version. Version identifiers can be arbitrary strings, so use the timestamp to find newer versions.
492 Example ``format=json`` reply:
496 {"versions": [[23, 1307700892], [28, 1307700898], ...]}
498 Example ``format=xml`` reply:
502 <?xml version="1.0" encoding="UTF-8"?>
504 <version timestamp="1307700892">23</version>
505 <version timestamp="1307700898">28</version>
506 <version timestamp="...">...</version>
509 The ``Range`` header may include multiple ranges, as outlined in RFC2616. Then the ``Content-Type`` of the reply will be ``multipart/byteranges`` and each part will include a ``Content-Range`` header.
511 ========================== ===============================
512 Reply Header Name Value
513 ========================== ===============================
514 ETag The ETag of the object
515 Content-Length The size of the data returned
516 Content-Type The MIME content type of the object
517 Content-Range The range of data included (only on a single range request)
518 Last-Modified The last object modification date (regardless of version)
519 Content-Encoding The encoding of the object (optional)
520 Content-Disposition The presentation style of the object (optional)
521 X-Object-Version The object's version identifier
522 X-Object-Version-Timestamp The object's version timestamp
523 X-Object-Modified-By The user that comitted the object's version
524 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
525 X-Object-Public Object is publicly accessible (optional) (**TBD**)
526 X-Object-Meta-* Optional user defined metadata
527 ========================== ===============================
531 =========================== ==============================
532 Return Code Description
533 =========================== ==============================
534 200 (OK) The request succeeded
535 206 (Partial Content) The range request succeeded
536 304 (Not Modified) The object has not been modified
537 412 (Precondition Failed) The condition set can not be satisfied
538 416 (Range Not Satisfiable) The requested range is out of limits
539 =========================== ==============================
545 ==================== ================================
546 Request Header Name Value
547 ==================== ================================
548 ETag The MD5 hash of the object (optional to check written data)
549 Content-Length The size of the data written
550 Content-Type The MIME content type of the object
551 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
552 X-Copy-From The source path in the form ``/<container>/<object>``
553 X-Move-From The source path in the form ``/<container>/<object>``
554 X-Source-Version The source version to copy from
555 Content-Encoding The encoding of the object (optional)
556 Content-Disposition The presentation style of the object (optional)
557 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
558 X-Object-Public Object is publicly accessible (optional) (**TBD**)
559 X-Object-Meta-* Optional user defined metadata
560 ==================== ================================
564 ========================== ===============================
565 Reply Header Name Value
566 ========================== ===============================
567 ETag The MD5 hash of the object (on create)
568 ========================== ===============================
572 =========================== ==============================
573 Return Code Description
574 =========================== ==============================
575 201 (Created) The object has been created
576 411 (Length Required) Missing ``Content-Length`` or ``Content-Type`` in the request
577 422 (Unprocessable Entity) The MD5 checksum of the data written to the storage system does not match the (optionally) supplied ETag value
578 =========================== ==============================
584 ==================== ================================
585 Request Header Name Value
586 ==================== ================================
587 Destination The destination path in the form ``/<container>/<object>``
588 Content-Type The MIME content type of the object (optional)
589 Content-Encoding The encoding of the object (optional)
590 Content-Disposition The presentation style of the object (optional)
591 X-Source-Version The source version to copy from
592 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
593 X-Object-Public Object is publicly accessible (optional) (**TBD**)
594 X-Object-Meta-* Optional user defined metadata
595 ==================== ================================
597 Refer to ``POST`` for a description of request headers. Metadata is also copied, updated with any values defined.
599 No reply content/headers.
601 =========================== ==============================
602 Return Code Description
603 =========================== ==============================
604 201 (Created) The object has been created
605 =========================== ==============================
611 Same as ``COPY``, without the ``X-Source-Version`` request header. The ``MOVE`` operation is always applied on the latest version.
617 ====================== ============================================
618 Request Parameter Name Value
619 ====================== ============================================
620 update Do not replace metadata (no value parameter)
621 ====================== ============================================
625 ==================== ================================
626 Request Header Name Value
627 ==================== ================================
628 Content-Length The size of the data written (optional, to update)
629 Content-Type The MIME content type of the object (optional, to update)
630 Content-Range The range of data supplied (optional, to update)
631 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
632 Content-Encoding The encoding of the object (optional)
633 Content-Disposition The presentation style of the object (optional)
634 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
635 X-Object-Public Object is publicly accessible (optional) (**TBD**)
636 X-Object-Meta-* Optional user defined metadata
637 ==================== ================================
639 The ``Content-Encoding``, ``Content-Disposition``, ``X-Object-Manifest``, ``X-Object-Public`` (**TBD**) and ``X-Object-Meta-*`` headers are considered to be user defined metadata. An operation without the ``update`` parameter will overwrite all previous values and remove any keys not supplied. When using ``update`` any metadata with an empty value will be deleted.
641 To update an object's data:
643 * Set ``Content-Type`` to ``application/octet-stream``. If ``Content-Type`` has some other value, it will be ignored and only the metadata will be updated.
644 * Supply ``Content-Length`` (except if using chunked transfers), ``Content-Type`` and ``Content-Range`` headers.
645 * Set ``Content-Range`` as specified in RFC2616, with the following differences:
647 * Client software MAY omit ``last-byte-pos`` of if the length of the range being transferred is unknown or difficult to determine.
648 * Client software SHOULD not specify the ``instance-length`` (use a ``*``), unless there is a reason for performing a size check at the server.
649 * If ``Content-Range`` used has a ``byte-range-resp-spec = *``, data supplied will be appended to the object.
651 A data update will trigger an ETag change. The new ETag will not correspond to the object's MD5 sum (**TBD**) and will be included in reply headers.
653 No reply content. No reply headers if only metadata is updated.
655 ========================== ===============================
656 Reply Header Name Value
657 ========================== ===============================
658 ETag The new ETag of the object (data updated)
659 ========================== ===============================
663 =========================== ==============================
664 Return Code Description
665 =========================== ==============================
666 202 (Accepted) The request has been accepted (not a data update)
667 204 (No Content) The request succeeded (data updated)
668 411 (Length Required) Missing ``Content-Length`` in the request
669 416 (Range Not Satisfiable) The supplied range is invalid
670 =========================== ==============================
676 No request parameters/headers.
678 No reply content/headers.
680 =========================== ==============================
681 Return Code Description
682 =========================== ==============================
683 204 (No Content) The request succeeded
684 =========================== ==============================
689 Objects that are marked as public, via the ``X-Object-Public`` meta (**TBD**), are also available at the corresponding URI ``https://hostname/public/<account>/<container>/<object>`` for ``HEAD`` or ``GET``. Requests for public objects do not need to include an ``X-Auth-Token``. Pithos will ignore request parameters and only include the following headers in the reply (all ``X-Object-*`` meta is hidden).
691 ========================== ===============================
692 Reply Header Name Value
693 ========================== ===============================
694 ETag The ETag of the object
695 Content-Length The size of the data returned
696 Content-Type The MIME content type of the object
697 Content-Range The range of data included (only on a single range request)
698 Last-Modified The last object modification date (regardless of version)
699 Content-Encoding The encoding of the object (optional)
700 Content-Disposition The presentation style of the object (optional)
701 ========================== ===============================
706 List of differences from the OOS API:
708 * Support for ``X-Account-Meta-*`` style headers at the account level. Use ``POST`` to update.
709 * Support for ``X-Container-Meta-*`` style headers at the account level. Can be set when creating via ``PUT``. Use ``POST`` to update.
710 * Header ``X-Container-Object-Meta`` at the container level and parameter ``meta`` in container listings.
711 * Headers ``X-Container-Block-*`` at the container level, exposing the underlying storage characteristics.
712 * All metadata replies, at all levels, include latest modification information.
713 * At all levels, a ``GET`` request may use ``If-Modified-Since`` and ``If-Unmodified-Since`` headers.
714 * Container/object lists include all associated metadata if the reply is of type json/xml. Some names are kept to their OOS API equivalents for compatibility.
715 * Object metadata allowed, in addition to ``X-Object-Meta-*``: ``Content-Encoding``, ``Content-Disposition``, ``X-Object-Manifest``, ``X-Object-Public`` (**TBD**). These are all replaced with every update operation, except if using the ``update`` parameter (in which case individual keys can also be deleted). Deleting meta by providing empty values also works when copying/moving an object.
716 * Multi-range object GET support as outlined in RFC2616.
717 * Object hashmap retrieval through GET and the ``format`` parameter.
718 * Partial object updates through POST, using the ``Content-Length``, ``Content-Type``, ``Content-Range`` and ``Transfer-Encoding`` headers.
719 * Object ``MOVE`` support.
720 * Time-variant account/container listings via the ``until`` parameter.
721 * Object versions - parameter ``version`` in HEAD/GET (list versions with GET), ``X-Object-Version-*`` meta in replies, ``X-Source-Version`` in PUT/COPY.
722 * Publicly accessible objects via ``https://hostname/public``. Control with ``X-Object-Public`` (**TBD**).
723 * Large object support with ``X-Object-Manifest``.
724 * Trace the user that created/modified an object with ``X-Object-Modified-By``.
726 Clarifications/suggestions:
728 * Authentication is done by another system. The token is used in the same way, but it is obtained differently. The top level ``GET`` request is kept compatible with the OOS API and allows for guest/testing operations.
729 * Some processing is done in the variable part of all ``X-*-Meta-*`` headers. If it includes underscores, they will be converted to dashes and the first letter of all intra-dash strings will be capitalized.
730 * A ``GET`` reply for a level will include all headers of the corresponding ``HEAD`` request.
731 * To avoid conflicts between objects and virtual directory markers in container listings, it is recommended that object names do not end with the delimiter used.
732 * The ``Accept`` header may be used in requests instead of the ``format`` parameter to specify the desired reply format. The parameter overrides the header.
733 * Container/object lists use a ``200`` return code if the reply is of type json/xml. The reply will include an empty json/xml.
734 * In headers, dates are formatted according to RFC 1123. In extended information listings, dates are formatted according to ISO 8601.
735 * The ``Last-Modified`` header value always reflects the actual latest change timestamp, regardless of time control parameters and version requests. Time precondition checks with ``If-Modified-Since`` and ``If-Unmodified-Since`` headers are applied to this value.
736 * A copy/move using ``PUT``/``COPY``/``MOVE`` will always update metadata, keeping all old values except the ones redefined in the request headers.
737 * A ``HEAD`` or ``GET`` for an ``X-Object-Manifest`` object, will include modified ``Content-Length`` and ``ETag`` headers, according to the characteristics of the objects under the specified prefix. The ``Etag`` will be the MD5 hash of the corresponding ETags concatenated. In extended container listings there is no metadata processing.
745 Hopefully this API will allow for a multitude of client implementations, each supporting a different device or operating system. All clients will be able to manipulate containers and objects - even software only designed for OOS API compatibility. But a Pithos interface should not be only about showing containers and folders. There are some extra user interface elements and functionalities that should be common to all implementations.
747 Upon entrance to the service, a user is presented with the following elements - which can be represented as folders or with other related icons:
749 * The ``home`` element, which is used as the default entry point to the user's "files". Objects under ``home`` are represented in the usual hierarchical organization of folders and files.
750 * The ``trash`` element, which contains files that have been marked for deletion, but can still be recovered.
751 * The ``shared`` element, which contains all objects shared by the user to other users of the system.
752 * The ``others`` element, which contains all objects that other users share with the user.
753 * The ``tags`` element, which lists the names of tags the user has defined. This can be an entry point to list all files that have been assigned a specific tag or manage tags in general (remove a tag completely, rename a tag etc.).
754 * The ``groups`` element, which contains the names of groups the user has defined. Each group consists of a user list. Group creation, deletion, and manipulation is carried out by actions originating here.
756 Objects in Pithos can be:
758 * Assigned custom tags.
759 * Moved to trash and then deleted.
760 * Shared with specific permissions.
761 * Made public (shared with non-Pithos users).
762 * Restored from previous versions.
764 Some of these functions are performed by the client software and some by the Pithos server. Client-driven functionality is based on specific metadata that should be handled equally across implementations. These metadata names are discussed in the next chapter.
766 Conventions and Metadata Specification
767 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
769 Pithos clients should use the ``pithos`` container for all Pithos objects. Object names use the ``/`` delimiter to impose a hierarchy of folders and files.
771 At the object level, tags are implemented by managing metadata keys. The client software should allow the user to use any string as a tag (except ``trash``) and then set the corresponding ``X-Object-Meta-<tag>`` key at the server. The API extensions provided, allow for listing all tags in a container and filtering object listings based on one or more tags. The tag list is sufficient for implementing the ``tags`` element, either as a special, virtual folder (as done in the first version of Pithos), or as an application menu.
773 To manage the deletion of files use the same API and the ``X-Object-Meta-Trash`` key. The string ``trash`` can not be used as a tag. The ``trash`` element should be presented as a folder, although with no hierarchy.
775 The metadata specification is summarized in the following table.
777 =========================== ==============================
779 =========================== ==============================
780 X-Object-Meta-Trash Set to ``true`` if the object has been moved to the trash
781 X-Object-Meta-* Use for other tags that apply to the object
782 =========================== ==============================
784 Recommended Practices and Examples
785 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
787 Assuming an authentication token is obtained (**TBD**), the following high-level operations are available - shown with ``curl``:
789 * Get account information ::
792 -H "X-Auth-Token: 0000" \
793 https://pithos.dev.grnet.gr/v1/user
795 * List available containers ::
798 -H "X-Auth-Token: 0000" \
799 https://pithos.dev.grnet.gr/v1/user
801 * Get container information ::
804 -H "X-Auth-Token: 0000" \
805 https://pithos.dev.grnet.gr/v1/user/pithos
807 * Add a new container ::
810 -H "X-Auth-Token: 0000" \
811 https://pithos.dev.grnet.gr/v1/user/test
813 * Delete a container ::
815 curl -X DELETE -D - \
816 -H "X-Auth-Token: 0000" \
817 https://pithos.dev.grnet.gr/v1/user/test
819 * List objects in a container ::
822 -H "X-Auth-Token: 0000" \
823 https://pithos.dev.grnet.gr/v1/user/pithos
825 * List objects in a container (extended reply) ::
828 -H "X-Auth-Token: 0000" \
829 https://pithos.dev.grnet.gr/v1/user/pithos?format=json
831 It is recommended that extended replies are cached and subsequent requests utilize the ``If-Modified-Since`` header.
833 * List metadata keys used by objects in a container
835 Will be in the ``X-Container-Object-Meta`` reply header, included in container information or object list (``HEAD`` or ``GET``).
837 * List objects in a container having a specific meta defined ::
840 -H "X-Auth-Token: 0000" \
841 https://pithos.dev.grnet.gr/v1/user/pithos?meta=trash
843 This is the recommended way of tagging/retrieving objects in trash.
845 * Retrieve an object ::
848 -H "X-Auth-Token: 0000" \
849 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
851 * Retrieve an object (specific ranges of data) ::
854 -H "X-Auth-Token: 0000" \
855 -H "Range: bytes=0-9" \
856 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
858 This will return the first 10 bytes. To get the first 10, bytes 30-39 and the last 100 use ``Range: bytes=0-9,30-39,-100``.
860 * Add a new object (folder type) (**TBD**) ::
863 -H "X-Auth-Token: 0000" \
864 -H "Content-Type: application/folder" \
865 https://pithos.dev.grnet.gr/v1/user/pithos/folder
867 * Add a new object ::
870 -H "X-Auth-Token: 0000" \
871 -H "Content-Type: text/plain" \
873 https://pithos.dev.grnet.gr/v1/user/pithos/folder/EXAMPLE.txt
875 * Update an object ::
878 -H "X-Auth-Token: 0000" \
879 -H "Content-Length: 10" \
880 -H "Content-Type: application/octet-stream" \
881 -H "Content-Range: bytes 10-19/*" \
883 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
885 This will update bytes 10-19 with the data specified.
887 * Update an object (append) ::
890 -H "X-Auth-Token: 0000" \
891 -H "Content-Length: 10" \
892 -H "Content-Type: application/octet-stream" \
893 -H "Content-Range: bytes */*" \
895 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
897 * Add object metadata ::
900 -H "X-Auth-Token: 0000" \
901 -H "X-Object-Meta-First: first_meta_value" \
902 -H "X-Object-Meta-Second: second_meta_value" \
903 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
905 * Delete object metadata ::
908 -H "X-Auth-Token: 0000" \
909 -H "X-Object-Meta-First: first_meta_value" \
910 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
912 Metadata can only be "set". To delete ``X-Object-Meta-Second``, reset all metadata.
914 * Delete an object ::
916 curl -X DELETE -D - \
917 -H "X-Auth-Token: 0000" \
918 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
projects / pithos / blob