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. Pithos will store sharing permissions per object and enforce corresponding authorization policies. 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 0.5 (July 22, 2011) Object update from another object's data.
29 \ Support object truncate.
30 \ Create object using a standard HTML form.
31 \ Purge container/object history.
32 \ List other accounts that share objects with a user.
33 \ List shared containers/objects.
34 \ Update implementation guidelines.
35 \ Check preconditions when creating/updating objects.
36 0.4 (July 01, 2011) Object permissions and account groups.
37 \ Control versioning behavior and container quotas with container policy directives.
38 \ Support updating/deleting individual metadata with ``POST``.
39 \ Create object using hashmap.
40 0.3 (June 14, 2011) Large object support with ``X-Object-Manifest``.
41 \ Allow for publicly available objects via ``https://hostname/public``.
42 \ Support time-variant account/container listings.
43 \ Add source version when duplicating with ``PUT``/``COPY``.
44 \ Request version in object ``HEAD``/``GET`` requests (list versions with ``GET``).
45 0.2 (May 31, 2011) Add object meta listing and filtering in containers.
46 \ Include underlying storage characteristics in container meta.
47 \ Support for partial object updates through ``POST``.
48 \ Expose object hashmaps through ``GET``.
49 \ Support for multi-range object ``GET`` requests.
50 0.1 (May 17, 2011) Initial release. Based on OpenStack Object Storage Developer Guide API v1 (Apr. 15, 2011).
51 ========================= ================================
56 The URI requests supported by the Pithos API follow one of the following forms:
58 * Top level: ``https://hostname/v1/``
59 * Account level: ``https://hostname/v1/<account>``
60 * Container level: ``https://hostname/v1/<account>/<container>``
61 * Object level: ``https://hostname/v1/<account>/<container>/<object>``
63 All requests must include an ``X-Auth-Token`` - as a header, or a parameter. The process of obtaining the token is still to be determined (**TBD**).
65 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.
67 ========================= ================================
68 Return Code Description
69 ========================= ================================
70 400 (Bad Request) The request is invalid
71 401 (Unauthorized) Request not allowed
72 404 (Not Found) The requested resource was not found
73 503 (Service Unavailable) The request cannot be completed because of an internal error
74 ========================= ================================
81 ========= ==================
83 ========= ==================
84 GET Authentication (for compatibility with the OOS API) or list allowed accounts
85 ========= ==================
90 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.
92 ================ =====================
93 Return Code Description
94 ================ =====================
95 204 (No Content) The request succeeded
96 ================ =====================
98 If an ``X-Auth-Token`` is already present, the operation will be interpreted as a request to list other accounts that share objects to the user.
100 ====================== =========================
101 Request Parameter Name Value
102 ====================== =========================
103 limit The amount of results requested (default is 10000)
104 marker Return containers with name lexicographically after marker
105 format Optional extended reply type (can be ``json`` or ``xml``)
106 ====================== =========================
108 The reply is a list of account names.
109 If a ``format=xml`` or ``format=json`` argument is given, extended information on the accounts will be returned, serialized in the chosen format.
110 For each account, the information will include the following (names will be in lower case and with hyphens replaced with underscores):
112 =========================== ============================
114 =========================== ============================
115 name The name of the account
116 last_modified The last account modification date (regardless of ``until``)
117 =========================== ============================
119 Example ``format=json`` reply:
123 [{"name": "user", "last_modified": "2011-07-19T10:48:16"}, ...]
125 Example ``format=xml`` reply:
129 <?xml version="1.0" encoding="UTF-8"?>
133 <last_modified>2011-07-19T10:48:16</last_modified>
135 <account>...</account>
138 =========================== =====================
139 Return Code Description
140 =========================== =====================
141 200 (OK) The request succeeded
142 204 (No Content) The user has no access to other accounts (only for non-extended replies)
143 =========================== =====================
145 Will use a ``200`` return code if the reply is of type json/xml.
152 ========= ==================
153 Operation Description
154 ========= ==================
155 HEAD Retrieve account metadata
157 POST Update account metadata
158 ========= ==================
163 ==================== ===========================
164 Request Header Name Value
165 ==================== ===========================
166 If-Modified-Since Retrieve if account has changed since provided timestamp
167 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
168 ==================== ===========================
172 ====================== ===================================
173 Request Parameter Name Value
174 ====================== ===================================
175 until Optional timestamp
176 ====================== ===================================
178 Cross-user requests are not allowed to use ``until`` and only include the account modification date in the reply.
180 ========================== =====================
181 Reply Header Name Value
182 ========================== =====================
183 X-Account-Container-Count The total number of containers
184 X-Account-Object-Count The total number of objects (**TBD**)
185 X-Account-Bytes-Used The total number of bytes stored
186 X-Account-Bytes-Remaining The total number of bytes remaining (**TBD**)
187 X-Account-Last-Login The last login (**TBD**)
188 X-Account-Until-Timestamp The last account modification date until the timestamp provided
189 X-Account-Group-* Optional user defined groups
190 X-Account-Meta-* Optional user defined metadata
191 Last-Modified The last account modification date (regardless of ``until``)
192 ========================== =====================
196 ================ =====================
197 Return Code Description
198 ================ =====================
199 204 (No Content) The request succeeded
200 ================ =====================
206 ==================== ===========================
207 Request Header Name Value
208 ==================== ===========================
209 If-Modified-Since Retrieve if account has changed since provided timestamp
210 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
211 ==================== ===========================
215 ====================== =========================
216 Request Parameter Name Value
217 ====================== =========================
218 limit The amount of results requested (default is 10000)
219 marker Return containers with name lexicographically after marker
220 format Optional extended reply type (can be ``json`` or ``xml``)
221 shared Show only shared containers (no value parameter)
222 until Optional timestamp
223 ====================== =========================
225 The reply is a list of container names. Account headers (as in a ``HEAD`` request) will also be included.
226 Cross-user requests are not allowed to use ``until`` and only include the account/container modification dates in the reply.
228 If a ``format=xml`` or ``format=json`` argument is given, extended information on the containers will be returned, serialized in the chosen format.
229 For each container, the information will include all container metadata (names will be in lower case and with hyphens replaced with underscores):
231 =========================== ============================
233 =========================== ============================
234 name The name of the container
235 count The number of objects inside the container
236 bytes The total size of the objects inside the container
237 last_modified The last container modification date (regardless of ``until``)
238 x_container_until_timestamp The last container modification date until the timestamp provided
239 x_container_policy_* Container behavior and limits
240 x_container_meta_* Optional user defined metadata
241 =========================== ============================
243 For examples of container details returned in JSON/XML formats refer to the OOS API documentation.
245 =========================== =====================
246 Return Code Description
247 =========================== =====================
248 200 (OK) The request succeeded
249 204 (No Content) The account has no containers (only for non-extended replies)
250 304 (Not Modified) The account has not been modified
251 412 (Precondition Failed) The condition set can not be satisfied
252 =========================== =====================
254 Will use a ``200`` return code if the reply is of type json/xml.
260 ==================== ===========================
261 Request Header Name Value
262 ==================== ===========================
263 X-Account-Group-* Optional user defined groups
264 X-Account-Meta-* Optional user defined metadata
265 ==================== ===========================
269 ====================== ============================================
270 Request Parameter Name Value
271 ====================== ============================================
272 update Do not replace metadata/groups (no value parameter)
273 ====================== ============================================
275 No reply content/headers.
277 The operation will overwrite all user defined metadata, except if ``update`` is defined.
278 To create a group, include an ``X-Account-Group-*`` header with the name in the key and a comma separated list of user names in the value. If no ``X-Account-Group-*`` header is present, no changes will be applied to groups. The ``update`` parameter also applies to groups. To delete a specific group, use ``update`` and an empty header value.
280 ================ ===============================
281 Return Code Description
282 ================ ===============================
283 202 (Accepted) The request has been accepted
284 ================ ===============================
292 ========= ============================
293 Operation Description
294 ========= ============================
295 HEAD Retrieve container metadata
297 PUT Create/update container
298 POST Update container metadata
299 DELETE Delete container
300 ========= ============================
306 ==================== ===========================
307 Request Header Name Value
308 ==================== ===========================
309 If-Modified-Since Retrieve if container has changed since provided timestamp
310 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
311 ==================== ===========================
315 ====================== ===================================
316 Request Parameter Name Value
317 ====================== ===================================
318 until Optional timestamp
319 ====================== ===================================
321 Cross-user requests are not allowed to use ``until`` and only include the container modification date in the reply.
323 =========================== ===============================
324 Reply Header Name Value
325 =========================== ===============================
326 X-Container-Object-Count The total number of objects in the container
327 X-Container-Bytes-Used The total number of bytes of all objects stored
328 X-Container-Block-Size The block size used by the storage backend
329 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
330 X-Container-Until-Timestamp The last container modification date until the timestamp provided
331 X-Container-Object-Meta A list with all meta keys used by objects
332 X-Container-Policy-* Container behavior and limits
333 X-Container-Meta-* Optional user defined metadata
334 Last-Modified The last container modification date (regardless of ``until``)
335 =========================== ===============================
337 The keys returned in ``X-Container-Object-Meta`` are all the unique strings after the ``X-Object-Meta-`` prefix, formatted as a comma-separated list. See container ``PUT`` for a reference of policy directives.
339 ================ ===============================
340 Return Code Description
341 ================ ===============================
342 204 (No Content) The request succeeded
343 ================ ===============================
349 ==================== ===========================
350 Request Header Name Value
351 ==================== ===========================
352 If-Modified-Since Retrieve if container has changed since provided timestamp
353 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
354 ==================== ===========================
358 ====================== ===================================
359 Request Parameter Name Value
360 ====================== ===================================
361 limit The amount of results requested (default is 10000)
362 marker Return containers with name lexicographically after marker
363 prefix Return objects starting with prefix
364 delimiter Return objects up to the delimiter (discussion follows)
365 path Assume ``prefix=path`` and ``delimiter=/``
366 format Optional extended reply type (can be ``json`` or ``xml``)
367 meta Return objects having the specified meta keys (can be a comma separated list)
368 shared Show only shared objects (no value parameter)
369 until Optional timestamp
370 ====================== ===================================
372 The ``path`` parameter overrides ``prefix`` and ``delimiter``. When using ``path``, results will include objects ending in ``delimiter``.
374 The keys given with ``meta`` will be matched with the strings after the ``X-Object-Meta-`` prefix.
376 The reply is a list of object names. Container headers (as in a ``HEAD`` request) will also be included.
377 Cross-user requests are not allowed to use ``until`` and include the following limited set of headers in the reply:
379 =========================== ===============================
380 Reply Header Name Value
381 =========================== ===============================
382 X-Container-Block-Size The block size used by the storage backend
383 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
384 X-Container-Object-Meta A list with all meta keys used by allowed objects (**TBD**)
385 Last-Modified The last container modification date
386 =========================== ===============================
388 If a ``format=xml`` or ``format=json`` argument is given, extended information on the objects will be returned, serialized in the chosen format.
389 For each object, the information will include all object metadata (names will be in lower case and with hyphens replaced with underscores):
391 ========================== ======================================
393 ========================== ======================================
394 name The name of the object
395 hash The ETag of the object
396 bytes The size of the object
397 content_type The MIME content type of the object
398 content_encoding The encoding of the object (optional)
399 content-disposition The presentation style of the object (optional)
400 last_modified The last object modification date (regardless of version)
401 x_object_version The object's version identifier
402 x_object_version_timestamp The object's version timestamp
403 x_object_modified_by The user that committed the object's version
404 x_object_manifest Object parts prefix in ``<container>/<object>`` form (optional)
405 x_object_sharing Object permissions (optional)
406 x_object_shared_by Object inheriting permissions (optional)
407 x_object_public Object's publicly accessible URI (optional)
408 x_object_meta_* Optional user defined metadata
409 ========================== ======================================
411 Extended replies may also include virtual directory markers in separate sections of the ``json`` or ``xml`` results.
412 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.
413 In JSON results they appear as dictionaries with only a ``"subdir"`` key. In XML results they appear interleaved with ``<object>`` tags as ``<subdir name="..." />``.
414 In case there is an object with the same name as a virtual directory marker, the object will be returned.
416 For examples of object details returned in JSON/XML formats refer to the OOS API documentation.
418 =========================== ===============================
419 Return Code Description
420 =========================== ===============================
421 200 (OK) The request succeeded
422 204 (No Content) The account has no containers (only for non-extended replies)
423 304 (Not Modified) The container has not been modified
424 412 (Precondition Failed) The condition set can not be satisfied
425 =========================== ===============================
427 Will use a ``200`` return code if the reply is of type json/xml.
433 ==================== ================================
434 Request Header Name Value
435 ==================== ================================
436 X-Container-Policy-* Container behavior and limits
437 X-Container-Meta-* Optional user defined metadata
438 ==================== ================================
440 No reply content/headers.
442 If no policy is defined, the container will be created with the default values.
443 Available policy directives:
445 * ``versioning``: Set to ``auto``, ``manual`` or ``none`` (default is ``manual``)
446 * ``quota``: Size limit in KB (default is ``0`` - unlimited)
448 ================ ===============================
449 Return Code Description
450 ================ ===============================
451 201 (Created) The container has been created
452 202 (Accepted) The request has been accepted
453 ================ ===============================
459 ==================== ================================
460 Request Header Name Value
461 ==================== ================================
462 X-Container-Policy-* Container behavior and limits
463 X-Container-Meta-* Optional user defined metadata
464 ==================== ================================
468 ====================== ============================================
469 Request Parameter Name Value
470 ====================== ============================================
471 update Do not replace metadata/policy (no value parameter)
472 ====================== ============================================
474 No reply content/headers.
476 The operation will overwrite all user defined metadata, except if ``update`` is defined.
477 To change policy, include an ``X-Container-Policy-*`` header with the name in the key. If no ``X-Container-Policy-*`` header is present, no changes will be applied to policy. The ``update`` parameter also applies to policy - deleted values will revert to defaults. To delete/revert a specific policy directive, use ``update`` and an empty header value. See container ``PUT`` for a reference of policy directives.
479 ================ ===============================
480 Return Code Description
481 ================ ===============================
482 202 (Accepted) The request has been accepted
483 ================ ===============================
489 ====================== ===================================
490 Request Parameter Name Value
491 ====================== ===================================
492 until Optional timestamp
493 ====================== ===================================
495 If ``until`` is defined, the container is "purged" up to that time (the history of all objects up to then is deleted).
497 No reply content/headers.
499 ================ ===============================
500 Return Code Description
501 ================ ===============================
502 204 (No Content) The request succeeded
503 409 (Conflict) The container is not empty
504 ================ ===============================
512 ========= =================================
513 Operation Description
514 ========= =================================
515 HEAD Retrieve object metadata
517 PUT Write object data or copy/move object
520 POST Update object metadata/data
522 ========= =================================
528 ==================== ================================
529 Request Header Name Value
530 ==================== ================================
531 If-Match Retrieve if ETags match
532 If-None-Match Retrieve if ETags don't match
533 If-Modified-Since Retrieve if object has changed since provided timestamp
534 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
535 ==================== ================================
539 ====================== ===================================
540 Request Parameter Name Value
541 ====================== ===================================
542 version Optional version identifier
543 ====================== ===================================
547 ========================== ===============================
548 Reply Header Name Value
549 ========================== ===============================
550 ETag The ETag of the object
551 Content-Length The size of the object
552 Content-Type The MIME content type of the object
553 Last-Modified The last object modification date (regardless of version)
554 Content-Encoding The encoding of the object (optional)
555 Content-Disposition The presentation style of the object (optional)
556 X-Object-Version The object's version identifier
557 X-Object-Version-Timestamp The object's version timestamp
558 X-Object-Modified-By The user that comitted the object's version
559 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
560 X-Object-Sharing Object permissions (optional)
561 X-Object-Shared-By Object inheriting permissions (optional)
562 X-Object-Public Object's publicly accessible URI (optional)
563 X-Object-Meta-* Optional user defined metadata
564 ========================== ===============================
568 ================ ===============================
569 Return Code Description
570 ================ ===============================
571 200 (No Content) The request succeeded
572 ================ ===============================
578 ==================== ================================
579 Request Header Name Value
580 ==================== ================================
581 Range Optional range of data to retrieve
582 If-Range Retrieve the missing part if entity is unchanged; otherwise, retrieve the entire new entity (used together with Range header)
583 If-Match Retrieve if ETags match
584 If-None-Match Retrieve if ETags don't match
585 If-Modified-Since Retrieve if object has changed since provided timestamp
586 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
587 ==================== ================================
591 ====================== ===================================
592 Request Parameter Name Value
593 ====================== ===================================
594 format Optional extended reply type (can be ``json`` or ``xml``)
595 version Optional version identifier or ``list`` (specify a format if requesting a list)
596 ====================== ===================================
598 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.
600 Hashmaps expose the underlying storage format of the object. Note that each hash is computed after trimming trailing null bytes of the corresponding block.
602 Example ``format=json`` reply:
606 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
608 Example ``format=xml`` reply:
612 <?xml version="1.0" encoding="UTF-8"?>
613 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
614 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
618 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.
620 Example ``format=json`` reply:
624 {"versions": [[23, 1307700892], [28, 1307700898], ...]}
626 Example ``format=xml`` reply:
630 <?xml version="1.0" encoding="UTF-8"?>
632 <version timestamp="1307700892">23</version>
633 <version timestamp="1307700898">28</version>
634 <version timestamp="...">...</version>
637 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.
639 ========================== ===============================
640 Reply Header Name Value
641 ========================== ===============================
642 ETag The ETag of the object
643 Content-Length The size of the data returned
644 Content-Type The MIME content type of the object
645 Content-Range The range of data included (only on a single range request)
646 Last-Modified The last object modification date (regardless of version)
647 Content-Encoding The encoding of the object (optional)
648 Content-Disposition The presentation style of the object (optional)
649 X-Object-Version The object's version identifier
650 X-Object-Version-Timestamp The object's version timestamp
651 X-Object-Modified-By The user that comitted the object's version
652 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
653 X-Object-Sharing Object permissions (optional)
654 X-Object-Shared-By Object inheriting permissions (optional)
655 X-Object-Public Object's publicly accessible URI (optional)
656 X-Object-Meta-* Optional user defined metadata
657 ========================== ===============================
661 =========================== ==============================
662 Return Code Description
663 =========================== ==============================
664 200 (OK) The request succeeded
665 206 (Partial Content) The range request succeeded
666 304 (Not Modified) The object has not been modified
667 412 (Precondition Failed) The condition set can not be satisfied
668 416 (Range Not Satisfiable) The requested range is out of limits
669 =========================== ==============================
675 ==================== ================================
676 Request Header Name Value
677 ==================== ================================
678 If-Match Put if ETags match with current object
679 If-None-Match Put if ETags don't match with current object
680 ETag The MD5 hash of the object (optional to check written data)
681 Content-Length The size of the data written
682 Content-Type The MIME content type of the object
683 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
684 X-Copy-From The source path in the form ``/<container>/<object>``
685 X-Move-From The source path in the form ``/<container>/<object>``
686 X-Source-Version The source version to copy from
687 Content-Encoding The encoding of the object (optional)
688 Content-Disposition The presentation style of the object (optional)
689 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
690 X-Object-Sharing Object permissions (optional)
691 X-Object-Public Object is publicly accessible (optional)
692 X-Object-Meta-* Optional user defined metadata
693 ==================== ================================
697 ====================== ===================================
698 Request Parameter Name Value
699 ====================== ===================================
700 format Optional extended request type (can be ``json``) to create the object by suppling its hashmap instead
701 ====================== ===================================
703 The request is the object's data (or part of it), except if a hashmap is provided with the ``format`` parameter. If format is used and all different parts are stored in the server, the object is created, otherwise the server returns Conflict (409) with the list of the missing parts.
705 Hashmaps expose the underlying storage format of the object.
707 Example ``format=json`` request:
711 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
713 Example ``format=xml`` request:
717 <?xml version="1.0" encoding="UTF-8"?>
718 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
719 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
723 ========================== ===============================
724 Reply Header Name Value
725 ========================== ===============================
726 ETag The MD5 hash of the object (on create)
727 ========================== ===============================
729 The ``X-Object-Sharing`` header may include either a ``read=...`` comma-separated user/group list, or a ``write=...`` comma-separated user/group list, or both separated by a semicolon (``;``). Groups are specified as ``<account>:<group>``. To publish the object, set ``X-Object-Public`` to ``true``. To unpublish, set to ``false``, or use an empty header value.
731 =========================== ==============================
732 Return Code Description
733 =========================== ==============================
734 201 (Created) The object has been created
735 409 (Conflict) The object can not be created from the provided hashmap, or there are conflicting permissions (a list of missing hashes, or a conflicting sharing path will be included in the reply - in JSON format)
736 411 (Length Required) Missing ``Content-Length`` or ``Content-Type`` in the request
737 422 (Unprocessable Entity) The MD5 checksum of the data written to the storage system does not match the (optionally) supplied ETag value
738 =========================== ==============================
744 ==================== ================================
745 Request Header Name Value
746 ==================== ================================
747 If-Match Proceed if ETags match with object
748 If-None-Match Proceed if ETags don't match with object
749 Destination The destination path in the form ``/<container>/<object>``
750 Content-Type The MIME content type of the object (optional)
751 Content-Encoding The encoding of the object (optional)
752 Content-Disposition The presentation style of the object (optional)
753 X-Source-Version The source version to copy from
754 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
755 X-Object-Sharing Object permissions (optional)
756 X-Object-Public Object is publicly accessible (optional)
757 X-Object-Meta-* Optional user defined metadata
758 ==================== ================================
760 Refer to ``PUT``/``POST`` for a description of request headers. Metadata is also copied, updated with any values defined. Sharing/publishing options are not copied.
762 No reply content/headers.
764 =========================== ==============================
765 Return Code Description
766 =========================== ==============================
767 201 (Created) The object has been created
768 409 (Conflict) There are conflicting permissions (a conflicting sharing path will be included in the reply - in JSON format)
769 =========================== ==============================
775 Same as ``COPY``, without the ``X-Source-Version`` request header. The ``MOVE`` operation is always applied on the latest version.
781 ==================== ================================
782 Request Header Name Value
783 ==================== ================================
784 If-Match Proceed if ETags match with object
785 If-None-Match Proceed if ETags don't match with object
786 Content-Length The size of the data written (optional, to update)
787 Content-Type The MIME content type of the object (optional, to update)
788 Content-Range The range of data supplied (optional, to update)
789 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
790 Content-Encoding The encoding of the object (optional)
791 Content-Disposition The presentation style of the object (optional)
792 X-Source-Object Update with data from the object at path ``/<container>/<object>`` (optional, to update)
793 X-Source-Version The source version to update from (optional, to update)
794 X-Object-Bytes The updated object's final size (optional, when updating)
795 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
796 X-Object-Sharing Object permissions (optional)
797 X-Object-Public Object is publicly accessible (optional)
798 X-Object-Meta-* Optional user defined metadata
799 ==================== ================================
803 ====================== ============================================
804 Request Parameter Name Value
805 ====================== ============================================
806 update Do not replace metadata (no value parameter)
807 ====================== ============================================
809 The ``Content-Encoding``, ``Content-Disposition``, ``X-Object-Manifest`` 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.
811 To change permissions, include an ``X-Object-Sharing`` header (as defined in ``PUT``). To publish, include an ``X-Object-Public`` header, with a value of ``true``. If no such headers are defined, no changes will be applied to sharing/public. Use empty values to remove permissions/unpublish (unpublishing also works with ``false`` as a header value). Sharing options are applied to the object - not its versions.
813 To update an object's data:
815 * Either set ``Content-Type`` to ``application/octet-stream``, or provide an object with ``X-Source-Object``. If ``Content-Type`` has some other value, it will be ignored and only the metadata will be updated.
816 * If the data is supplied in the request (using ``Content-Type`` instead of ``X-Source-Object``), a valid ``Content-Length`` header is required - except if using chunked transfers (set ``Transfer-Encoding`` to ``chunked``).
817 * Set ``Content-Range`` as specified in RFC2616, with the following differences:
819 * Client software MAY omit ``last-byte-pos`` of if the length of the range being transferred is unknown or difficult to determine.
820 * Client software SHOULD not specify the ``instance-length`` (use a ``*``), unless there is a reason for performing a size check at the server.
821 * If ``Content-Range`` used has a ``byte-range-resp-spec = *``, data will be appended to the object.
823 Optionally, truncate the updated object to the desired length with the ``X-Object-Bytes`` header.
825 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.
827 No reply content. No reply headers if only metadata is updated.
829 ========================== ===============================
830 Reply Header Name Value
831 ========================== ===============================
832 ETag The new ETag of the object (data updated)
833 ========================== ===============================
837 =========================== ==============================
838 Return Code Description
839 =========================== ==============================
840 202 (Accepted) The request has been accepted (not a data update)
841 204 (No Content) The request succeeded (data updated)
842 409 (Conflict) There are conflicting permissions (a conflicting sharing path will be included in the reply - in JSON format)
843 411 (Length Required) Missing ``Content-Length`` in the request
844 416 (Range Not Satisfiable) The supplied range is invalid
845 =========================== ==============================
847 The ``POST`` method can also be used for creating an object via a standard HTML form. If the request ``Content-Type`` is ``multipart/form-data``, none of the above headers will be processed. The form should have exactly two fields, as in the following example. ::
849 <form method="post" action="https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt" enctype="multipart/form-data">
850 <input type="hidden" name="X-Auth-Token" value="0000">
851 <input type="file" name="X-Object-Data">
852 <input type="submit">
855 This will create/override the object with the given name, as if using ``PUT``. The ``Content-Type`` of the object will be set to the value of the corresponding header sent in the part of the request containing the data. Metadata, sharing and other object attributes can not be set this way.
857 ========================== ===============================
858 Reply Header Name Value
859 ========================== ===============================
860 ETag The MD5 hash of the object
861 ========================== ===============================
865 =========================== ==============================
866 Return Code Description
867 =========================== ==============================
868 201 (Created) The object has been created
869 =========================== ==============================
875 ====================== ===================================
876 Request Parameter Name Value
877 ====================== ===================================
878 until Optional timestamp
879 ====================== ===================================
881 If ``until`` is defined, the object is "purged" up to that time (the history up to then is deleted).
883 No reply content/headers.
885 =========================== ==============================
886 Return Code Description
887 =========================== ==============================
888 204 (No Content) The request succeeded
889 =========================== ==============================
891 Sharing and Public Objects
892 ^^^^^^^^^^^^^^^^^^^^^^^^^^
894 Read and write control in Pithos is managed by setting appropriate permissions with the ``X-Object-Sharing`` header. The permissions are applied using prefix-based inheritance. Thus, each set of authorization directives is applied to all objects sharing the same prefix with the object where the corresponding ``X-Object-Sharing`` header is defined. For simplicity, nested/overlapping permissions are not allowed. Setting ``X-Object-Sharing`` will fail, if the object is already "covered", or another object with a longer common-prefix name already has permissions. When retrieving an object, the ``X-Object-Shared-By`` header reports where it gets its permissions from. If not present, the object is the actual source of authorization directives.
896 A user may ``GET`` another account or container. The result will include a limited reply, containing only the allowed containers or objects respectively. A top-level request with an authentication token, will return a list of allowed accounts, so the user can easily find out which other users share objects.
898 Objects that are marked as public, via the ``X-Object-Public`` meta, are also available at the corresponding URI returned 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):
900 ========================== ===============================
901 Reply Header Name Value
902 ========================== ===============================
903 ETag The ETag of the object
904 Content-Length The size of the data returned
905 Content-Type The MIME content type of the object
906 Content-Range The range of data included (only on a single range request)
907 Last-Modified The last object modification date (regardless of version)
908 Content-Encoding The encoding of the object (optional)
909 Content-Disposition The presentation style of the object (optional)
910 ========================== ===============================
912 Public objects are not included and do not influence cross-user listings. They are, however, readable by all users.
917 List of differences from the OOS API:
919 * Support for ``X-Account-Meta-*`` style headers at the account level. Use ``POST`` to update.
920 * Support for ``X-Container-Meta-*`` style headers at the container level. Can be set when creating via ``PUT``. Use ``POST`` to update.
921 * Header ``X-Container-Object-Meta`` at the container level and parameter ``meta`` in container listings.
922 * Container policies to manage behavior and limits.
923 * Headers ``X-Container-Block-*`` at the container level, exposing the underlying storage characteristics.
924 * All metadata replies, at all levels, include latest modification information.
925 * At all levels, a ``HEAD`` or ``GET`` request may use ``If-Modified-Since`` and ``If-Unmodified-Since`` headers.
926 * 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.
927 * Option to include only shared containers/objects in listings.
928 * Object metadata allowed, in addition to ``X-Object-Meta-*``: ``Content-Encoding``, ``Content-Disposition``, ``X-Object-Manifest``. 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.
929 * Multi-range object ``GET`` support as outlined in RFC2616.
930 * Object hashmap retrieval through ``GET`` and the ``format`` parameter.
931 * Object create via hashmap through ``PUT`` and the ``format`` parameter.
932 * Object create using ``POST`` to support standard HTML forms.
933 * Partial object updates through ``POST``, using the ``Content-Length``, ``Content-Type``, ``Content-Range`` and ``Transfer-Encoding`` headers. Use another object's data to update with ``X-Source-Object`` and ``X-Source-Version``. Truncate with ``X-Object-Bytes``.
934 * Object ``MOVE`` support.
935 * Conditional object create/update operations, using ``If-Match`` and ``If-None-Match`` headers.
936 * Time-variant account/container listings via the ``until`` parameter.
937 * Object versions - parameter ``version`` in ``HEAD``/``GET`` (list versions with ``GET``), ``X-Object-Version-*`` meta in replies, ``X-Source-Version`` in ``PUT``/``COPY``.
938 * Sharing/publishing with ``X-Object-Sharing``, ``X-Object-Public`` at the object level. Cross-user operations are allowed - controlled by sharing directives. Permissions may include groups defined with ``X-Account-Group-*`` at the account level. These apply to the object - not its versions.
939 * Support for prefix-based inheritance when enforcing permissions. Parent object carrying the authorization directives is reported in ``X-Object-Shared-By``.
940 * Large object support with ``X-Object-Manifest``.
941 * Trace the user that created/modified an object with ``X-Object-Modified-By``.
942 * Purge container/object history with the ``until`` parameter in ``DELETE``.
944 Clarifications/suggestions:
946 * 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.
947 * 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.
948 * A ``GET`` reply for a level will include all headers of the corresponding ``HEAD`` request.
949 * 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.
950 * The ``Accept`` header may be used in requests instead of the ``format`` parameter to specify the desired reply format. The parameter overrides the header (**TBD**).
951 * Container/object lists use a ``200`` return code if the reply is of type json/xml. The reply will include an empty json/xml.
952 * In headers, dates are formatted according to RFC 1123. In extended information listings, the ``last_modified`` field is formatted according to ISO 8601 (for OOS API compatibility). All other fields (Pithos extensions) use integer tiemstamps.
953 * 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.
954 * A copy/move using ``PUT``/``COPY``/``MOVE`` will always update metadata, keeping all old values except the ones redefined in the request headers.
955 * 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.
963 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.
965 Upon entrance to the service, a user is presented with the following elements - which can be represented as folders or with other related icons:
967 * 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.
968 * The ``trash`` element, which contains files that have been marked for deletion, but can still be recovered.
969 * The ``shared`` element, which contains all objects shared by the user to other users of the system.
970 * The ``others`` element, which contains all objects that other users share with the user.
971 * 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.).
972 * 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.
973 * The ``history`` element, which allows browsing past instances of ``home`` and - optionally - ``trash``.
975 Objects in Pithos can be:
977 * Assigned custom tags.
978 * Moved to trash and then deleted.
979 * Shared with specific permissions.
980 * Made public (shared with non-Pithos users).
981 * Restored from previous versions.
983 Some of these functions are performed by the client software and some by the Pithos server.
985 Implementation Guidelines
986 ^^^^^^^^^^^^^^^^^^^^^^^^^
988 Pithos clients should use the ``pithos`` and ``trash`` containers for active and inactive objects respectively. If any of these containers is not found, the client software should create it, without interrupting the user's workflow. The ``home`` element corresponds to ``pithos`` and the ``trash`` element to ``trash``. Use ``PUT`` with the ``X-Move-From`` header, or ``MOVE`` to transfer objects from one container to the other. Use ``DELETE`` to remove from ``pithos`` without trashing, or to remove from ``trash``. When moving objects, detect naming conflicts with the ``If-Match`` or ``If-None-Match`` headers. Such conflicts should be resolved by the user.
990 Object names should use the ``/`` delimiter to impose a hierarchy of folders and files.
992 The ``shared`` element should be implemented as a read-only view of the ``pithos`` container, using the ``shared`` parameter when listing objects. The ``others`` element, should start with a top-level ``GET`` to retrieve the list of accounts accessible to the user. It is suggested that the client software hides the next step of navigation - the container - if it only includes ``pithos`` and forwards the user directly to the objects.
994 Public objects are not included in ``shared`` and ``others`` listings. It is suggested that they are marked in a visually distinctive way in ``pithos`` listings (for example using an icon overlay).
996 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 and 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.
998 A special application menu, or a section in application preferences, should be devoted to managing groups (the ``groups`` element). All group-related actions are implemented at the account level.
1000 Browsing past versions of objects should be available both at the object and the container level. At the object level, a list of past versions can be included in the screen showing details or more information on the object (metadata, tags, permissions, etc.). At the container level, it is suggested that clients use a ``history`` element, which presents to the user a read-only, time-variable view of ``pithos`` contents. This can be accomplished via the ``until`` parameter in listings. Optionally, ``history`` may include ``trash``.
1002 Recommended Practices and Examples
1003 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1005 Assuming an authentication token is obtained (**TBD**), the following high-level operations are available - shown with ``curl``:
1007 * Get account information ::
1010 -H "X-Auth-Token: 0000" \
1011 https://pithos.dev.grnet.gr/v1/user
1013 * List available containers ::
1016 -H "X-Auth-Token: 0000" \
1017 https://pithos.dev.grnet.gr/v1/user
1019 * Get container information ::
1022 -H "X-Auth-Token: 0000" \
1023 https://pithos.dev.grnet.gr/v1/user/pithos
1025 * Add a new container ::
1028 -H "X-Auth-Token: 0000" \
1029 https://pithos.dev.grnet.gr/v1/user/test
1031 * Delete a container ::
1033 curl -X DELETE -D - \
1034 -H "X-Auth-Token: 0000" \
1035 https://pithos.dev.grnet.gr/v1/user/test
1037 * List objects in a container ::
1040 -H "X-Auth-Token: 0000" \
1041 https://pithos.dev.grnet.gr/v1/user/pithos
1043 * List objects in a container (extended reply) ::
1046 -H "X-Auth-Token: 0000" \
1047 https://pithos.dev.grnet.gr/v1/user/pithos?format=json
1049 It is recommended that extended replies are cached and subsequent requests utilize the ``If-Modified-Since`` header.
1051 * List metadata keys used by objects in a container
1053 Will be in the ``X-Container-Object-Meta`` reply header, included in container information or object list (``HEAD`` or ``GET``).
1055 * List objects in a container having a specific meta defined ::
1058 -H "X-Auth-Token: 0000" \
1059 https://pithos.dev.grnet.gr/v1/user/pithos?meta=favorites
1061 * Retrieve an object ::
1064 -H "X-Auth-Token: 0000" \
1065 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1067 * Retrieve an object (specific ranges of data) ::
1070 -H "X-Auth-Token: 0000" \
1071 -H "Range: bytes=0-9" \
1072 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1074 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``.
1076 * Add a new object (folder type) (**TBD**) ::
1079 -H "X-Auth-Token: 0000" \
1080 -H "Content-Type: application/folder" \
1081 https://pithos.dev.grnet.gr/v1/user/pithos/folder
1083 * Add a new object ::
1086 -H "X-Auth-Token: 0000" \
1087 -H "Content-Type: text/plain" \
1089 https://pithos.dev.grnet.gr/v1/user/pithos/folder/EXAMPLE.txt
1091 * Update an object ::
1094 -H "X-Auth-Token: 0000" \
1095 -H "Content-Length: 10" \
1096 -H "Content-Type: application/octet-stream" \
1097 -H "Content-Range: bytes 10-19/*" \
1099 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1101 This will update bytes 10-19 with the data specified.
1103 * Update an object (append) ::
1106 -H "X-Auth-Token: 0000" \
1107 -H "Content-Length: 10" \
1108 -H "Content-Type: application/octet-stream" \
1109 -H "Content-Range: bytes */*" \
1111 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1113 * Update an object (truncate) ::
1116 -H "X-Auth-Token: 0000" \
1117 -H "X-Source-Object: /folder/EXAMPLE.txt" \
1118 -H "Content-Range: bytes 0-0/*" \
1119 -H "X-Object-Bytes: 0" \
1120 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1122 This will truncate the object to 0 bytes.
1124 * Add object metadata ::
1127 -H "X-Auth-Token: 0000" \
1128 -H "X-Object-Meta-First: first_meta_value" \
1129 -H "X-Object-Meta-Second: second_meta_value" \
1130 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1132 * Delete object metadata ::
1135 -H "X-Auth-Token: 0000" \
1136 -H "X-Object-Meta-First: first_meta_value" \
1137 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1139 Metadata can only be "set". To delete ``X-Object-Meta-Second``, reset all metadata.
1141 * Delete an object ::
1143 curl -X DELETE -D - \
1144 -H "X-Auth-Token: 0000" \
1145 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt