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 19, 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 0.4 (July 01, 2011) Object permissions and account groups.
34 \ Control versioning behavior and container quotas with container policy directives.
35 \ Support updating/deleting individual metadata with ``POST``.
36 \ Create object using hashmap.
37 0.3 (June 14, 2011) Large object support with ``X-Object-Manifest``.
38 \ Allow for publicly available objects via ``https://hostname/public``.
39 \ Support time-variant account/container listings.
40 \ Add source version when duplicating with ``PUT``/``COPY``.
41 \ Request version in object ``HEAD``/``GET`` requests (list versions with ``GET``).
42 0.2 (May 31, 2011) Add object meta listing and filtering in containers.
43 \ Include underlying storage characteristics in container meta.
44 \ Support for partial object updates through ``POST``.
45 \ Expose object hashmaps through ``GET``.
46 \ Support for multi-range object ``GET`` requests.
47 0.1 (May 17, 2011) Initial release. Based on OpenStack Object Storage Developer Guide API v1 (Apr. 15, 2011).
48 ========================= ================================
53 The URI requests supported by the Pithos API follow one of the following forms:
55 * Top level: ``https://hostname/v1/``
56 * Account level: ``https://hostname/v1/<account>``
57 * Container level: ``https://hostname/v1/<account>/<container>``
58 * Object level: ``https://hostname/v1/<account>/<container>/<object>``
60 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**).
62 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.
64 ========================= ================================
65 Return Code Description
66 ========================= ================================
67 400 (Bad Request) The request is invalid
68 401 (Unauthorized) Request not allowed
69 404 (Not Found) The requested resource was not found
70 503 (Service Unavailable) The request cannot be completed because of an internal error
71 ========================= ================================
78 ========= ==================
80 ========= ==================
81 GET Authentication (for compatibility with the OOS API) or list allowed accounts
82 ========= ==================
87 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.
89 ================ =====================
90 Return Code Description
91 ================ =====================
92 204 (No Content) The request succeeded
93 ================ =====================
95 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.
97 ====================== =========================
98 Request Parameter Name Value
99 ====================== =========================
100 limit The amount of results requested (default is 10000)
101 marker Return containers with name lexicographically after marker
102 format Optional extended reply type (can be ``json`` or ``xml``)
103 ====================== =========================
105 The reply is a list of account names.
106 If a ``format=xml`` or ``format=json`` argument is given, extended information on the containers will be returned, serialized in the chosen format.
107 For each account, the information will include the following (names will be in lower case and with hyphens replaced with underscores):
109 =========================== ============================
111 =========================== ============================
112 name The name of the account
113 last_modified The last container modification date (regardless of ``until``)
114 =========================== ============================
116 Example ``format=json`` reply:
120 [{"name": "user", "last_modified": "2011-07-19T10:48:16"}, ...]
122 Example ``format=xml`` reply:
126 <?xml version="1.0" encoding="UTF-8"?>
130 <last_modified>2011-07-19T10:48:16</last_modified>
132 <account>...</account>
135 =========================== =====================
136 Return Code Description
137 =========================== =====================
138 200 (OK) The request succeeded
139 204 (No Content) The account has no containers (only for non-extended replies)
140 =========================== =====================
142 Will use a ``200`` return code if the reply is of type json/xml.
149 ========= ==================
150 Operation Description
151 ========= ==================
152 HEAD Retrieve account metadata
154 POST Update account metadata
155 ========= ==================
160 ====================== ===================================
161 Request Parameter Name Value
162 ====================== ===================================
163 until Optional timestamp
164 ====================== ===================================
166 Cross-user requests are not allowed to use ``until`` and only include the account modification date in the reply.
168 ========================== =====================
169 Reply Header Name Value
170 ========================== =====================
171 X-Account-Container-Count The total number of containers
172 X-Account-Object-Count The total number of objects (**TBD**)
173 X-Account-Bytes-Used The total number of bytes stored
174 X-Account-Bytes-Remaining The total number of bytes remaining (**TBD**)
175 X-Account-Last-Login The last login (**TBD**)
176 X-Account-Until-Timestamp The last account modification date until the timestamp provided
177 X-Account-Group-* Optional user defined groups
178 X-Account-Meta-* Optional user defined metadata
179 Last-Modified The last account modification date (regardless of ``until``)
180 ========================== =====================
184 ================ =====================
185 Return Code Description
186 ================ =====================
187 204 (No Content) The request succeeded
188 ================ =====================
194 ==================== ===========================
195 Request Header Name Value
196 ==================== ===========================
197 If-Modified-Since Retrieve if account has changed since provided timestamp
198 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
199 ==================== ===========================
203 ====================== =========================
204 Request Parameter Name Value
205 ====================== =========================
206 limit The amount of results requested (default is 10000)
207 marker Return containers with name lexicographically after marker
208 format Optional extended reply type (can be ``json`` or ``xml``)
209 until Optional timestamp
210 ====================== =========================
212 The reply is a list of container names. Account headers (as in a ``HEAD`` request) will also be included.
213 Cross-user requests are not allowed to use ``until`` and only include the account/container modification dates in the reply.
215 If a ``format=xml`` or ``format=json`` argument is given, extended information on the containers will be returned, serialized in the chosen format.
216 For each container, the information will include all container metadata (names will be in lower case and with hyphens replaced with underscores):
218 =========================== ============================
220 =========================== ============================
221 name The name of the container
222 count The number of objects inside the container
223 bytes The total size of the objects inside the container
224 last_modified The last container modification date (regardless of ``until``)
225 x_container_until_timestamp The last container modification date until the timestamp provided
226 x_container_policy_* Container behavior and limits
227 x_container_meta_* Optional user defined metadata
228 =========================== ============================
230 For examples of container details returned in JSON/XML formats refer to the OOS API documentation.
232 =========================== =====================
233 Return Code Description
234 =========================== =====================
235 200 (OK) The request succeeded
236 204 (No Content) The account has no containers (only for non-extended replies)
237 304 (Not Modified) The account has not been modified
238 412 (Precondition Failed) The condition set can not be satisfied
239 =========================== =====================
241 Will use a ``200`` return code if the reply is of type json/xml.
247 ====================== ============================================
248 Request Parameter Name Value
249 ====================== ============================================
250 update Do not replace metadata/groups (no value parameter)
251 ====================== ============================================
255 ==================== ===========================
256 Request Header Name Value
257 ==================== ===========================
258 X-Account-Group-* Optional user defined groups
259 X-Account-Meta-* Optional user defined metadata
260 ==================== ===========================
262 No reply content/headers.
264 The operation will overwrite all user defined metadata, except if ``update`` is defined.
265 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.
267 ================ ===============================
268 Return Code Description
269 ================ ===============================
270 202 (Accepted) The request has been accepted
271 ================ ===============================
279 ========= ============================
280 Operation Description
281 ========= ============================
282 HEAD Retrieve container metadata
284 PUT Create/update container
285 POST Update container metadata
286 DELETE Delete container
287 ========= ============================
293 ====================== ===================================
294 Request Parameter Name Value
295 ====================== ===================================
296 until Optional timestamp
297 ====================== ===================================
299 Cross-user requests are not allowed to use ``until`` and only include the container modification date in the reply.
301 =========================== ===============================
302 Reply Header Name Value
303 =========================== ===============================
304 X-Container-Object-Count The total number of objects in the container
305 X-Container-Bytes-Used The total number of bytes of all objects stored
306 X-Container-Block-Size The block size used by the storage backend
307 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
308 X-Container-Until-Timestamp The last container modification date until the timestamp provided
309 X-Container-Object-Meta A list with all meta keys used by objects
310 X-Container-Policy-* Container behavior and limits
311 X-Container-Meta-* Optional user defined metadata
312 Last-Modified The last container modification date (regardless of ``until``)
313 =========================== ===============================
315 The keys returned in ``X-Container-Object-Meta`` are all the unique strings after the ``X-Object-Meta-`` prefix. See container ``PUT`` for a reference of policy directives.
317 ================ ===============================
318 Return Code Description
319 ================ ===============================
320 204 (No Content) The request succeeded
321 ================ ===============================
327 ==================== ===========================
328 Request Header Name Value
329 ==================== ===========================
330 If-Modified-Since Retrieve if container has changed since provided timestamp
331 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
332 ==================== ===========================
336 ====================== ===================================
337 Request Parameter Name Value
338 ====================== ===================================
339 limit The amount of results requested (default is 10000)
340 marker Return containers with name lexicographically after marker
341 prefix Return objects starting with prefix
342 delimiter Return objects up to the delimiter (discussion follows)
343 path Assume ``prefix=path`` and ``delimiter=/``
344 format Optional extended reply type (can be ``json`` or ``xml``)
345 meta Return objects having the specified meta keys (can be a comma separated list)
346 until Optional timestamp
347 ====================== ===================================
349 The ``path`` parameter overrides ``prefix`` and ``delimiter``. When using ``path``, results will include objects ending in ``delimiter``.
351 The keys given with ``meta`` will be matched with the strings after the ``X-Object-Meta-`` prefix.
353 The reply is a list of object names. Container headers (as in a ``HEAD`` request) will also be included.
354 Cross-user requests are not allowed to use ``until`` and include the following limited set of headers in the reply:
356 =========================== ===============================
357 Reply Header Name Value
358 =========================== ===============================
359 X-Container-Block-Size The block size used by the storage backend
360 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
361 X-Container-Object-Meta A list with all meta keys used by allowed objects (**TBD**)
362 Last-Modified The last container modification date
363 =========================== ===============================
365 If a ``format=xml`` or ``format=json`` argument is given, extended information on the objects will be returned, serialized in the chosen format.
366 For each object, the information will include all object metadata (names will be in lower case and with hyphens replaced with underscores):
368 ========================== ======================================
370 ========================== ======================================
371 name The name of the object
372 hash The ETag of the object
373 bytes The size of the object
374 content_type The MIME content type of the object
375 content_encoding The encoding of the object (optional)
376 content-disposition The presentation style of the object (optional)
377 last_modified The last object modification date (regardless of version)
378 x_object_version The object's version identifier
379 x_object_version_timestamp The object's version timestamp
380 x_object_modified_by The user that committed the object's version
381 x_object_manifest Object parts prefix in ``<container>/<object>`` form (optional)
382 x_object_sharing Object permissions (optional)
383 x_object_shared_by Object inheriting permissions (optional)
384 x_object_public Object's publicly accessible URI (optional)
385 x_object_meta_* Optional user defined metadata
386 ========================== ======================================
388 Extended replies may also include virtual directory markers in separate sections of the ``json`` or ``xml`` results.
389 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.
390 In JSON results they appear as dictionaries with only a ``"subdir"`` key. In XML results they appear interleaved with ``<object>`` tags as ``<subdir name="..." />``.
391 In case there is an object with the same name as a virtual directory marker, the object will be returned.
393 For examples of object details returned in JSON/XML formats refer to the OOS API documentation.
395 =========================== ===============================
396 Return Code Description
397 =========================== ===============================
398 200 (OK) The request succeeded
399 204 (No Content) The account has no containers (only for non-extended replies)
400 304 (Not Modified) The container has not been modified
401 412 (Precondition Failed) The condition set can not be satisfied
402 =========================== ===============================
404 Will use a ``200`` return code if the reply is of type json/xml.
410 ==================== ================================
411 Request Header Name Value
412 ==================== ================================
413 X-Container-Policy-* Container behavior and limits
414 X-Container-Meta-* Optional user defined metadata
415 ==================== ================================
417 No reply content/headers.
419 If no policy is defined, the container will be created with the default values.
420 Available policy directives:
422 * ``versioning``: Set to ``auto``, ``manual`` or ``none`` (default is ``manual``)
423 * ``quota``: Size limit in KB (default is ``0`` - unlimited)
425 ================ ===============================
426 Return Code Description
427 ================ ===============================
428 201 (Created) The container has been created
429 202 (Accepted) The request has been accepted
430 ================ ===============================
436 ====================== ============================================
437 Request Parameter Name Value
438 ====================== ============================================
439 update Do not replace metadata/policy (no value parameter)
440 ====================== ============================================
444 ==================== ================================
445 Request Header Name Value
446 ==================== ================================
447 X-Container-Policy-* Container behavior and limits
448 X-Container-Meta-* Optional user defined metadata
449 ==================== ================================
451 No reply content/headers.
453 The operation will overwrite all user defined metadata, except if ``update`` is defined.
454 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.
456 ================ ===============================
457 Return Code Description
458 ================ ===============================
459 202 (Accepted) The request has been accepted
460 ================ ===============================
466 ====================== ===================================
467 Request Parameter Name Value
468 ====================== ===================================
469 until Optional timestamp
470 ====================== ===================================
472 If ``until`` is defined, the container is "purged" up to that time (the history of all objects up to then is deleted).
474 No reply content/headers.
476 ================ ===============================
477 Return Code Description
478 ================ ===============================
479 204 (No Content) The request succeeded
480 409 (Conflict) The container is not empty
481 ================ ===============================
489 ========= =================================
490 Operation Description
491 ========= =================================
492 HEAD Retrieve object metadata
494 PUT Write object data or copy/move object
497 POST Update object metadata/data
499 ========= =================================
505 ====================== ===================================
506 Request Parameter Name Value
507 ====================== ===================================
508 version Optional version identifier
509 ====================== ===================================
513 ========================== ===============================
514 Reply Header Name Value
515 ========================== ===============================
516 ETag The ETag of the object
517 Content-Length The size of the object
518 Content-Type The MIME content type of the object
519 Last-Modified The last object modification date (regardless of version)
520 Content-Encoding The encoding of the object (optional)
521 Content-Disposition The presentation style of the object (optional)
522 X-Object-Version The object's version identifier
523 X-Object-Version-Timestamp The object's version timestamp
524 X-Object-Modified-By The user that comitted the object's version
525 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
526 X-Object-Sharing Object permissions (optional)
527 X-Object-Shared-By Object inheriting permissions (optional)
528 X-Object-Public Object's publicly accessible URI (optional)
529 X-Object-Meta-* Optional user defined metadata
530 ========================== ===============================
534 ================ ===============================
535 Return Code Description
536 ================ ===============================
537 200 (No Content) The request succeeded
538 ================ ===============================
544 ==================== ================================
545 Request Header Name Value
546 ==================== ================================
547 Range Optional range of data to retrieve
548 If-Range Retrieve the missing part if entity is unchanged; otherwise, retrieve the entire new entity (used together with Range header)
549 If-Match Retrieve if ETags match
550 If-None-Match Retrieve if ETags don't match
551 If-Modified-Since Retrieve if object has changed since provided timestamp
552 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
553 ==================== ================================
557 ====================== ===================================
558 Request Parameter Name Value
559 ====================== ===================================
560 format Optional extended reply type (can be ``json`` or ``xml``)
561 version Optional version identifier or ``list`` (specify a format if requesting a list)
562 ====================== ===================================
564 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.
566 Hashmaps expose the underlying storage format of the object. Note that each hash is computed after trimming trailing null bytes of the corresponding block.
568 Example ``format=json`` reply:
572 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
574 Example ``format=xml`` reply:
578 <?xml version="1.0" encoding="UTF-8"?>
579 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
580 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
584 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.
586 Example ``format=json`` reply:
590 {"versions": [[23, 1307700892], [28, 1307700898], ...]}
592 Example ``format=xml`` reply:
596 <?xml version="1.0" encoding="UTF-8"?>
598 <version timestamp="1307700892">23</version>
599 <version timestamp="1307700898">28</version>
600 <version timestamp="...">...</version>
603 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.
605 ========================== ===============================
606 Reply Header Name Value
607 ========================== ===============================
608 ETag The ETag of the object
609 Content-Length The size of the data returned
610 Content-Type The MIME content type of the object
611 Content-Range The range of data included (only on a single range request)
612 Last-Modified The last object modification date (regardless of version)
613 Content-Encoding The encoding of the object (optional)
614 Content-Disposition The presentation style of the object (optional)
615 X-Object-Version The object's version identifier
616 X-Object-Version-Timestamp The object's version timestamp
617 X-Object-Modified-By The user that comitted the object's version
618 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
619 X-Object-Sharing Object permissions (optional)
620 X-Object-Shared-By Object inheriting permissions (optional)
621 X-Object-Public Object's publicly accessible URI (optional)
622 X-Object-Meta-* Optional user defined metadata
623 ========================== ===============================
627 =========================== ==============================
628 Return Code Description
629 =========================== ==============================
630 200 (OK) The request succeeded
631 206 (Partial Content) The range request succeeded
632 304 (Not Modified) The object has not been modified
633 412 (Precondition Failed) The condition set can not be satisfied
634 416 (Range Not Satisfiable) The requested range is out of limits
635 =========================== ==============================
641 ==================== ================================
642 Request Header Name Value
643 ==================== ================================
644 ETag The MD5 hash of the object (optional to check written data)
645 Content-Length The size of the data written
646 Content-Type The MIME content type of the object
647 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
648 X-Copy-From The source path in the form ``/<container>/<object>``
649 X-Move-From The source path in the form ``/<container>/<object>``
650 X-Source-Version The source version to copy from
651 Content-Encoding The encoding of the object (optional)
652 Content-Disposition The presentation style of the object (optional)
653 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
654 X-Object-Sharing Object permissions (optional)
655 X-Object-Public Object is publicly accessible (optional)
656 X-Object-Meta-* Optional user defined metadata
657 ==================== ================================
661 ====================== ===================================
662 Request Parameter Name Value
663 ====================== ===================================
664 format Optional extended request type (can be ``json``) to create the object by suppling its hashmap instead
665 ====================== ===================================
667 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.
669 Hashmaps expose the underlying storage format of the object.
671 Example ``format=json`` request:
675 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
677 Example ``format=xml`` request:
681 <?xml version="1.0" encoding="UTF-8"?>
682 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
683 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
687 ========================== ===============================
688 Reply Header Name Value
689 ========================== ===============================
690 ETag The MD5 hash of the object (on create)
691 ========================== ===============================
693 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.
695 =========================== ==============================
696 Return Code Description
697 =========================== ==============================
698 201 (Created) The object has been created
699 409 (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)
700 411 (Length Required) Missing ``Content-Length`` or ``Content-Type`` in the request
701 422 (Unprocessable Entity) The MD5 checksum of the data written to the storage system does not match the (optionally) supplied ETag value
702 =========================== ==============================
708 ==================== ================================
709 Request Header Name Value
710 ==================== ================================
711 Destination The destination path in the form ``/<container>/<object>``
712 Content-Type The MIME content type of the object (optional)
713 Content-Encoding The encoding of the object (optional)
714 Content-Disposition The presentation style of the object (optional)
715 X-Source-Version The source version to copy from
716 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
717 X-Object-Sharing Object permissions (optional)
718 X-Object-Public Object is publicly accessible (optional)
719 X-Object-Meta-* Optional user defined metadata
720 ==================== ================================
722 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.
724 No reply content/headers.
726 =========================== ==============================
727 Return Code Description
728 =========================== ==============================
729 201 (Created) The object has been created
730 409 (Conflict) There are conflicting permissions (a conflicting sharing path will be included in the reply - in JSON format)
731 =========================== ==============================
737 Same as ``COPY``, without the ``X-Source-Version`` request header. The ``MOVE`` operation is always applied on the latest version.
743 ====================== ============================================
744 Request Parameter Name Value
745 ====================== ============================================
746 update Do not replace metadata (no value parameter)
747 ====================== ============================================
751 ==================== ================================
752 Request Header Name Value
753 ==================== ================================
754 Content-Length The size of the data written (optional, to update)
755 Content-Type The MIME content type of the object (optional, to update)
756 Content-Range The range of data supplied (optional, to update)
757 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
758 Content-Encoding The encoding of the object (optional)
759 Content-Disposition The presentation style of the object (optional)
760 X-Source-Object Update with data from the object at path ``/<container>/<object>`` (optional, to update)
761 X-Source-Version The source version to update from (optional, to update)
762 X-Object-Bytes The updated object's final size (optional, when updating)
763 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
764 X-Object-Sharing Object permissions (optional)
765 X-Object-Public Object is publicly accessible (optional)
766 X-Object-Meta-* Optional user defined metadata
767 ==================== ================================
769 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.
771 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.
773 To update an object's data:
775 * 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.
776 * 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``).
777 * Set ``Content-Range`` as specified in RFC2616, with the following differences:
779 * Client software MAY omit ``last-byte-pos`` of if the length of the range being transferred is unknown or difficult to determine.
780 * Client software SHOULD not specify the ``instance-length`` (use a ``*``), unless there is a reason for performing a size check at the server.
781 * If ``Content-Range`` used has a ``byte-range-resp-spec = *``, data will be appended to the object.
783 Optionally, truncate the updated object to the desired length with the ``X-Object-Bytes`` header.
785 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.
787 No reply content. No reply headers if only metadata is updated.
789 ========================== ===============================
790 Reply Header Name Value
791 ========================== ===============================
792 ETag The new ETag of the object (data updated)
793 ========================== ===============================
797 =========================== ==============================
798 Return Code Description
799 =========================== ==============================
800 202 (Accepted) The request has been accepted (not a data update)
801 204 (No Content) The request succeeded (data updated)
802 409 (Conflict) There are conflicting permissions (a conflicting sharing path will be included in the reply - in JSON format)
803 411 (Length Required) Missing ``Content-Length`` in the request
804 416 (Range Not Satisfiable) The supplied range is invalid
805 =========================== ==============================
807 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. ::
809 <form method="post" action="https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt" enctype="multipart/form-data">
810 <input type="hidden" name="X-Auth-Token" value="0000">
811 <input type="file" name="X-Object-Data">
812 <input type="submit">
815 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.
817 ========================== ===============================
818 Reply Header Name Value
819 ========================== ===============================
820 ETag The MD5 hash of the object
821 ========================== ===============================
825 =========================== ==============================
826 Return Code Description
827 =========================== ==============================
828 201 (Created) The object has been created
829 =========================== ==============================
835 ====================== ===================================
836 Request Parameter Name Value
837 ====================== ===================================
838 until Optional timestamp
839 ====================== ===================================
841 If ``until`` is defined, the object is "purged" up to that time (the history up to then is deleted).
843 No reply content/headers.
845 =========================== ==============================
846 Return Code Description
847 =========================== ==============================
848 204 (No Content) The request succeeded
849 =========================== ==============================
851 Sharing and Public Objects
852 ^^^^^^^^^^^^^^^^^^^^^^^^^^
854 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.
856 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.
858 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):
860 ========================== ===============================
861 Reply Header Name Value
862 ========================== ===============================
863 ETag The ETag of the object
864 Content-Length The size of the data returned
865 Content-Type The MIME content type of the object
866 Content-Range The range of data included (only on a single range request)
867 Last-Modified The last object modification date (regardless of version)
868 Content-Encoding The encoding of the object (optional)
869 Content-Disposition The presentation style of the object (optional)
870 ========================== ===============================
872 Public objects are not included and do not influence cross-user listings. They are, however, readable by all users.
877 List of differences from the OOS API:
879 * Support for ``X-Account-Meta-*`` style headers at the account level. Use ``POST`` to update.
880 * Support for ``X-Container-Meta-*`` style headers at the container level. Can be set when creating via ``PUT``. Use ``POST`` to update.
881 * Header ``X-Container-Object-Meta`` at the container level and parameter ``meta`` in container listings.
882 * Container policies to manage behavior and limits.
883 * Headers ``X-Container-Block-*`` at the container level, exposing the underlying storage characteristics.
884 * All metadata replies, at all levels, include latest modification information.
885 * At all levels, a ``GET`` request may use ``If-Modified-Since`` and ``If-Unmodified-Since`` headers.
886 * 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.
887 * 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.
888 * Multi-range object ``GET`` support as outlined in RFC2616.
889 * Object hashmap retrieval through ``GET`` and the ``format`` parameter.
890 * Object create via hashmap through ``PUT`` and the ``format`` parameter.
891 * Object create using ``POST`` to support standard HTML forms.
892 * 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``.
893 * Object ``MOVE`` support.
894 * Time-variant account/container listings via the ``until`` parameter.
895 * Object versions - parameter ``version`` in ``HEAD``/``GET`` (list versions with ``GET``), ``X-Object-Version-*`` meta in replies, ``X-Source-Version`` in ``PUT``/``COPY``.
896 * 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.
897 * Support for prefix-based inheritance when enforcing permissions. Parent object carrying the authorization directives is reported in ``X-Object-Shared-By``.
898 * Large object support with ``X-Object-Manifest``.
899 * Trace the user that created/modified an object with ``X-Object-Modified-By``.
900 * Purge container/object history with the ``until`` parameter in ``DELETE``.
902 Clarifications/suggestions:
904 * 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.
905 * 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.
906 * A ``GET`` reply for a level will include all headers of the corresponding ``HEAD`` request.
907 * 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.
908 * 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**).
909 * Container/object lists use a ``200`` return code if the reply is of type json/xml. The reply will include an empty json/xml.
910 * In headers, dates are formatted according to RFC 1123. In extended information listings, dates are formatted according to ISO 8601.
911 * 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.
912 * A copy/move using ``PUT``/``COPY``/``MOVE`` will always update metadata, keeping all old values except the ones redefined in the request headers.
913 * 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.
921 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.
923 Upon entrance to the service, a user is presented with the following elements - which can be represented as folders or with other related icons:
925 * 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.
926 * The ``trash`` element, which contains files that have been marked for deletion, but can still be recovered.
927 * The ``shared`` element, which contains all objects shared by the user to other users of the system.
928 * The ``others`` element, which contains all objects that other users share with the user.
929 * 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.).
930 * 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.
932 Objects in Pithos can be:
934 * Assigned custom tags.
935 * Moved to trash and then deleted.
936 * Shared with specific permissions.
937 * Made public (shared with non-Pithos users).
938 * Restored from previous versions.
940 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.
942 Conventions and Metadata Specification
943 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
945 Pithos clients should use the ``pithos`` container for all Pithos objects. Object names use the ``/`` delimiter to impose a hierarchy of folders and files.
947 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 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.
949 The metadata specification is summarized in the following table.
951 =========================== ==============================
953 =========================== ==============================
954 X-Object-Meta-* Use for other tags that apply to the object
955 =========================== ==============================
957 Recommended Practices and Examples
958 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
960 Assuming an authentication token is obtained (**TBD**), the following high-level operations are available - shown with ``curl``:
962 * Get account information ::
965 -H "X-Auth-Token: 0000" \
966 https://pithos.dev.grnet.gr/v1/user
968 * List available containers ::
971 -H "X-Auth-Token: 0000" \
972 https://pithos.dev.grnet.gr/v1/user
974 * Get container information ::
977 -H "X-Auth-Token: 0000" \
978 https://pithos.dev.grnet.gr/v1/user/pithos
980 * Add a new container ::
983 -H "X-Auth-Token: 0000" \
984 https://pithos.dev.grnet.gr/v1/user/test
986 * Delete a container ::
988 curl -X DELETE -D - \
989 -H "X-Auth-Token: 0000" \
990 https://pithos.dev.grnet.gr/v1/user/test
992 * List objects in a container ::
995 -H "X-Auth-Token: 0000" \
996 https://pithos.dev.grnet.gr/v1/user/pithos
998 * List objects in a container (extended reply) ::
1001 -H "X-Auth-Token: 0000" \
1002 https://pithos.dev.grnet.gr/v1/user/pithos?format=json
1004 It is recommended that extended replies are cached and subsequent requests utilize the ``If-Modified-Since`` header.
1006 * List metadata keys used by objects in a container
1008 Will be in the ``X-Container-Object-Meta`` reply header, included in container information or object list (``HEAD`` or ``GET``).
1010 * List objects in a container having a specific meta defined ::
1013 -H "X-Auth-Token: 0000" \
1014 https://pithos.dev.grnet.gr/v1/user/pithos?meta=favorites
1016 * Retrieve an object ::
1019 -H "X-Auth-Token: 0000" \
1020 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1022 * Retrieve an object (specific ranges of data) ::
1025 -H "X-Auth-Token: 0000" \
1026 -H "Range: bytes=0-9" \
1027 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1029 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``.
1031 * Add a new object (folder type) (**TBD**) ::
1034 -H "X-Auth-Token: 0000" \
1035 -H "Content-Type: application/folder" \
1036 https://pithos.dev.grnet.gr/v1/user/pithos/folder
1038 * Add a new object ::
1041 -H "X-Auth-Token: 0000" \
1042 -H "Content-Type: text/plain" \
1044 https://pithos.dev.grnet.gr/v1/user/pithos/folder/EXAMPLE.txt
1046 * Update an object ::
1049 -H "X-Auth-Token: 0000" \
1050 -H "Content-Length: 10" \
1051 -H "Content-Type: application/octet-stream" \
1052 -H "Content-Range: bytes 10-19/*" \
1054 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1056 This will update bytes 10-19 with the data specified.
1058 * Update an object (append) ::
1061 -H "X-Auth-Token: 0000" \
1062 -H "Content-Length: 10" \
1063 -H "Content-Type: application/octet-stream" \
1064 -H "Content-Range: bytes */*" \
1066 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1068 * Update an object (truncate) ::
1071 -H "X-Auth-Token: 0000" \
1072 -H "X-Source-Object: /folder/EXAMPLE.txt" \
1073 -H "Content-Range: bytes 0-0/*" \
1074 -H "X-Object-Bytes: 0" \
1075 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1077 This will truncate the object to 0 bytes.
1079 * Add object metadata ::
1082 -H "X-Auth-Token: 0000" \
1083 -H "X-Object-Meta-First: first_meta_value" \
1084 -H "X-Object-Meta-Second: second_meta_value" \
1085 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1087 * Delete object metadata ::
1090 -H "X-Auth-Token: 0000" \
1091 -H "X-Object-Meta-First: first_meta_value" \
1092 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1094 Metadata can only be "set". To delete ``X-Object-Meta-Second``, reset all metadata.
1096 * Delete an object ::
1098 curl -X DELETE -D - \
1099 -H "X-Auth-Token: 0000" \
1100 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt