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 0.7 (Oct 4, 2011) Suggest upload/download methods using hashmaps.
29 \ Propose syncing algorithm.
30 \ Support cross-account object copy and move.
31 \ Pass token as a request parameter when using ``POST`` via an HTML form.
32 \ Optionally use source account to update object from another object.
33 \ Use container ``POST`` to upload missing blocks of data.
34 0.6 (Sept 13, 2011) Reply with Merkle hash as the ETag when updating objects.
35 \ Include version id in object replace/change replies.
36 \ Change conflict (409) replies format to text.
37 \ Tags should be migrated to a meta value.
38 \ Container ``PUT`` updates metadata/policy.
39 \ Report allowed actions in shared object replies.
40 \ Provide ``https://hostname/login`` for Shibboleth authentication.
41 \ Use ``hashmap`` parameter in object ``GET``/``PUT`` to use hashmaps.
42 0.5 (July 22, 2011) Object update from another object's data.
43 \ Support object truncate.
44 \ Create object using a standard HTML form.
45 \ Purge container/object history.
46 \ List other accounts that share objects with a user.
47 \ List shared containers/objects.
48 \ Update implementation guidelines.
49 \ Check preconditions when creating/updating objects.
50 0.4 (July 01, 2011) Object permissions and account groups.
51 \ Control versioning behavior and container quotas with container policy directives.
52 \ Support updating/deleting individual metadata with ``POST``.
53 \ Create object using hashmap.
54 0.3 (June 14, 2011) Large object support with ``X-Object-Manifest``.
55 \ Allow for publicly available objects via ``https://hostname/public``.
56 \ Support time-variant account/container listings.
57 \ Add source version when duplicating with ``PUT``/``COPY``.
58 \ Request version in object ``HEAD``/``GET`` requests (list versions with ``GET``).
59 0.2 (May 31, 2011) Add object meta listing and filtering in containers.
60 \ Include underlying storage characteristics in container meta.
61 \ Support for partial object updates through ``POST``.
62 \ Expose object hashmaps through ``GET``.
63 \ Support for multi-range object ``GET`` requests.
64 0.1 (May 17, 2011) Initial release. Based on OpenStack Object Storage Developer Guide API v1 (Apr. 15, 2011).
65 ========================= ================================
67 Pithos Users and Authentication
68 -------------------------------
70 Pithos keeps separate databases for users and objects.
72 Each user is uniquely identified by the ``Uniq`` field. This should be used as the user's account in the API. The API uses the ``Token`` field to authenticate a user, thus allowing cross-account requests. All API requests require a token.
74 User entries can be modified/added via the management interface available at ``https://hostname/admin``.
76 Pithos is also compatible with Shibboleth (http://shibboleth.internet2.edu/). The connection between Shibboleth and Pithos is done by ``https://hostname/login``. An application that wishes to connect to Pithos, but does not have a token, should redirect the user to the login URI.
78 The login URI accepts the following parameters:
80 ====================== =========================
81 Request Parameter Name Value
82 ====================== =========================
83 next The URI to redirect to when the process is finished
84 renew Force token renewal (no value parameter)
85 ====================== =========================
87 The login process starts by redirecting the user to an external URI (controlled by Shibboleth), where the actual authentication credentials are entered. Then, the user is redirected back to the login URI from Shibboleth, with various identification information in the request headers.
89 If the user does not exist in the database, Pithos adds the user and creates a random token. If the user exists, the token has not expired and ``renew`` is not set, the existing token is reused. Finally, the login URI redirects to the URI provided with ``next``, adding the ``user`` and ``token`` parameters, which contain the ``Uniq`` and ``Token`` fields respectively.
94 The URI requests supported by the Pithos API follow one of the following forms:
96 * Top level: ``https://hostname/v1/``
97 * Account level: ``https://hostname/v1/<account>``
98 * Container level: ``https://hostname/v1/<account>/<container>``
99 * Object level: ``https://hostname/v1/<account>/<container>/<object>``
101 All requests must include an ``X-Auth-Token`` - as a header, or a parameter.
103 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.
105 ========================= ================================
106 Return Code Description
107 ========================= ================================
108 400 (Bad Request) The request is invalid
109 401 (Unauthorized) Request not allowed
110 404 (Not Found) The requested resource was not found
111 503 (Service Unavailable) The request cannot be completed because of an internal error
112 ========================= ================================
119 ========= ==================
120 Operation Description
121 ========= ==================
122 GET Authentication (for compatibility with the OOS API) or list allowed accounts
123 ========= ==================
128 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.
130 ================ =====================
131 Return Code Description
132 ================ =====================
133 204 (No Content) The request succeeded
134 ================ =====================
136 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.
138 ====================== =========================
139 Request Parameter Name Value
140 ====================== =========================
141 limit The amount of results requested (default is 10000)
142 marker Return containers with name lexicographically after marker
143 format Optional extended reply type (can be ``json`` or ``xml``)
144 ====================== =========================
146 The reply is a list of account names.
147 If a ``format=xml`` or ``format=json`` argument is given, extended information on the accounts will be returned, serialized in the chosen format.
148 For each account, the information will include the following (names will be in lower case and with hyphens replaced with underscores):
150 =========================== ============================
152 =========================== ============================
153 name The name of the account
154 last_modified The last account modification date (regardless of ``until``)
155 =========================== ============================
157 Example ``format=json`` reply:
161 [{"name": "user", "last_modified": "2011-07-19T10:48:16"}, ...]
163 Example ``format=xml`` reply:
167 <?xml version="1.0" encoding="UTF-8"?>
171 <last_modified>2011-07-19T10:48:16</last_modified>
173 <account>...</account>
176 =========================== =====================
177 Return Code Description
178 =========================== =====================
179 200 (OK) The request succeeded
180 204 (No Content) The user has no access to other accounts (only for non-extended replies)
181 =========================== =====================
183 Will use a ``200`` return code if the reply is of type json/xml.
190 ========= ==================
191 Operation Description
192 ========= ==================
193 HEAD Retrieve account metadata
195 POST Update account metadata
196 ========= ==================
201 ==================== ===========================
202 Request Header Name Value
203 ==================== ===========================
204 If-Modified-Since Retrieve if account has changed since provided timestamp
205 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
206 ==================== ===========================
210 ====================== ===================================
211 Request Parameter Name Value
212 ====================== ===================================
213 until Optional timestamp
214 ====================== ===================================
216 Cross-user requests are not allowed to use ``until`` and only include the account modification date in the reply.
218 ========================== =====================
219 Reply Header Name Value
220 ========================== =====================
221 X-Account-Container-Count The total number of containers
222 X-Account-Object-Count The total number of objects (**TBD**)
223 X-Account-Bytes-Used The total number of bytes stored
224 X-Account-Bytes-Remaining The total number of bytes remaining
225 X-Account-Last-Login The last login (**TBD**)
226 X-Account-Until-Timestamp The last account modification date until the timestamp provided
227 X-Account-Group-* Optional user defined groups
228 X-Account-Meta-* Optional user defined metadata
229 Last-Modified The last account modification date (regardless of ``until``)
230 ========================== =====================
234 ================ =====================
235 Return Code Description
236 ================ =====================
237 204 (No Content) The request succeeded
238 ================ =====================
244 ==================== ===========================
245 Request Header Name Value
246 ==================== ===========================
247 If-Modified-Since Retrieve if account has changed since provided timestamp
248 If-Unmodified-Since Retrieve if account has not changed since provided timestamp
249 ==================== ===========================
253 ====================== =========================
254 Request Parameter Name Value
255 ====================== =========================
256 limit The amount of results requested (default is 10000)
257 marker Return containers with name lexicographically after marker
258 format Optional extended reply type (can be ``json`` or ``xml``)
259 shared Show only shared containers (no value parameter)
260 until Optional timestamp
261 ====================== =========================
263 The reply is a list of container names. Account headers (as in a ``HEAD`` request) will also be included.
264 Cross-user requests are not allowed to use ``until`` and only include the account/container modification dates in the reply.
266 If a ``format=xml`` or ``format=json`` argument is given, extended information on the containers will be returned, serialized in the chosen format.
267 For each container, the information will include all container metadata (names will be in lower case and with hyphens replaced with underscores):
269 =========================== ============================
271 =========================== ============================
272 name The name of the container
273 count The number of objects inside the container
274 bytes The total size of the objects inside the container
275 last_modified The last container modification date (regardless of ``until``)
276 x_container_until_timestamp The last container modification date until the timestamp provided
277 x_container_policy_* Container behavior and limits
278 x_container_meta_* Optional user defined metadata
279 =========================== ============================
281 For examples of container details returned in JSON/XML formats refer to the OOS API documentation.
283 =========================== =====================
284 Return Code Description
285 =========================== =====================
286 200 (OK) The request succeeded
287 204 (No Content) The account has no containers (only for non-extended replies)
288 304 (Not Modified) The account has not been modified
289 412 (Precondition Failed) The condition set can not be satisfied
290 =========================== =====================
292 Will use a ``200`` return code if the reply is of type json/xml.
298 ==================== ===========================
299 Request Header Name Value
300 ==================== ===========================
301 X-Account-Group-* Optional user defined groups
302 X-Account-Meta-* Optional user defined metadata
303 ==================== ===========================
307 ====================== ============================================
308 Request Parameter Name Value
309 ====================== ============================================
310 update Do not replace metadata/groups (no value parameter)
311 ====================== ============================================
313 No reply content/headers.
315 The operation will overwrite all user defined metadata, except if ``update`` is defined.
316 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.
318 ================ ===============================
319 Return Code Description
320 ================ ===============================
321 202 (Accepted) The request has been accepted
322 ================ ===============================
330 ========= ============================
331 Operation Description
332 ========= ============================
333 HEAD Retrieve container metadata
335 PUT Create/update container
336 POST Update container metadata
337 DELETE Delete container
338 ========= ============================
344 ==================== ===========================
345 Request Header Name Value
346 ==================== ===========================
347 If-Modified-Since Retrieve if container has changed since provided timestamp
348 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
349 ==================== ===========================
353 ====================== ===================================
354 Request Parameter Name Value
355 ====================== ===================================
356 until Optional timestamp
357 ====================== ===================================
359 Cross-user requests are not allowed to use ``until`` and only include the container modification date in the reply.
361 =========================== ===============================
362 Reply Header Name Value
363 =========================== ===============================
364 X-Container-Object-Count The total number of objects in the container
365 X-Container-Bytes-Used The total number of bytes of all objects stored
366 X-Container-Block-Size The block size used by the storage backend
367 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
368 X-Container-Until-Timestamp The last container modification date until the timestamp provided
369 X-Container-Object-Meta A list with all meta keys used by objects (**TBD**)
370 X-Container-Policy-* Container behavior and limits
371 X-Container-Meta-* Optional user defined metadata
372 Last-Modified The last container modification date (regardless of ``until``)
373 =========================== ===============================
375 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. (**TBD**)
377 ================ ===============================
378 Return Code Description
379 ================ ===============================
380 204 (No Content) The request succeeded
381 ================ ===============================
387 ==================== ===========================
388 Request Header Name Value
389 ==================== ===========================
390 If-Modified-Since Retrieve if container has changed since provided timestamp
391 If-Unmodified-Since Retrieve if container has not changed since provided timestamp
392 ==================== ===========================
396 ====================== ===================================
397 Request Parameter Name Value
398 ====================== ===================================
399 limit The amount of results requested (default is 10000)
400 marker Return containers with name lexicographically after marker
401 prefix Return objects starting with prefix
402 delimiter Return objects up to the delimiter (discussion follows)
403 path Assume ``prefix=path`` and ``delimiter=/``
404 format Optional extended reply type (can be ``json`` or ``xml``)
405 meta Return objects having the specified meta keys (can be a comma separated list)
406 shared Show only shared objects (no value parameter)
407 until Optional timestamp
408 ====================== ===================================
410 The ``path`` parameter overrides ``prefix`` and ``delimiter``. When using ``path``, results will include objects ending in ``delimiter``.
412 The keys given with ``meta`` will be matched with the strings after the ``X-Object-Meta-`` prefix.
414 The reply is a list of object names. Container headers (as in a ``HEAD`` request) will also be included.
415 Cross-user requests are not allowed to use ``until`` and include the following limited set of headers in the reply:
417 =========================== ===============================
418 Reply Header Name Value
419 =========================== ===============================
420 X-Container-Block-Size The block size used by the storage backend
421 X-Container-Block-Hash The hash algorithm used for block identifiers in object hashmaps
422 X-Container-Object-Meta A list with all meta keys used by allowed objects (**TBD**)
423 Last-Modified The last container modification date
424 =========================== ===============================
426 If a ``format=xml`` or ``format=json`` argument is given, extended information on the objects will be returned, serialized in the chosen format.
427 For each object, the information will include all object metadata (names will be in lower case and with hyphens replaced with underscores):
429 ========================== ======================================
431 ========================== ======================================
432 name The name of the object
433 hash The ETag of the object
434 bytes The size of the object
435 content_type The MIME content type of the object
436 content_encoding The encoding of the object (optional)
437 content-disposition The presentation style of the object (optional)
438 last_modified The last object modification date (regardless of version)
439 x_object_version The object's version identifier
440 x_object_version_timestamp The object's version timestamp
441 x_object_modified_by The user that committed the object's version
442 x_object_manifest Object parts prefix in ``<container>/<object>`` form (optional)
443 x_object_sharing Object permissions (optional)
444 x_object_shared_by Object inheriting permissions (optional)
445 x_object_allowed_to Allowed actions on object (optional)
446 x_object_public Object's publicly accessible URI (optional)
447 x_object_meta_* Optional user defined metadata
448 ========================== ======================================
450 Extended replies may also include virtual directory markers in separate sections of the ``json`` or ``xml`` results.
451 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.
452 In JSON results they appear as dictionaries with only a ``"subdir"`` key. In XML results they appear interleaved with ``<object>`` tags as ``<subdir name="..." />``.
453 In case there is an object with the same name as a virtual directory marker, the object will be returned.
455 For examples of object details returned in JSON/XML formats refer to the OOS API documentation.
457 =========================== ===============================
458 Return Code Description
459 =========================== ===============================
460 200 (OK) The request succeeded
461 204 (No Content) The account has no containers (only for non-extended replies)
462 304 (Not Modified) The container has not been modified
463 412 (Precondition Failed) The condition set can not be satisfied
464 =========================== ===============================
466 Will use a ``200`` return code if the reply is of type json/xml.
472 ==================== ================================
473 Request Header Name Value
474 ==================== ================================
475 X-Container-Policy-* Container behavior and limits
476 X-Container-Meta-* Optional user defined metadata
477 ==================== ================================
479 No reply content/headers.
481 If no policy is defined, the container will be created with the default values.
482 Available policy directives:
484 * ``versioning``: Set to ``auto``, ``manual`` or ``none`` (default is ``manual``)
485 * ``quota``: Size limit in KB (default is ``0`` - unlimited)
487 If the container already exists, the operation is equal to a ``POST`` with ``update`` defined.
489 ================ ===============================
490 Return Code Description
491 ================ ===============================
492 201 (Created) The container has been created
493 202 (Accepted) The request has been accepted
494 ================ ===============================
500 ==================== ================================
501 Request Header Name Value
502 ==================== ================================
503 Content-Length The size of the supplied data (optional, to upload)
504 Content-Type The MIME content type of the supplied data (optional, to upload)
505 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
506 X-Container-Policy-* Container behavior and limits
507 X-Container-Meta-* Optional user defined metadata
508 ==================== ================================
512 ====================== ============================================
513 Request Parameter Name Value
514 ====================== ============================================
515 update Do not replace metadata/policy (no value parameter)
516 ====================== ============================================
518 No reply content/headers, except when uploading data, where the reply consists of a list of hashes for the blocks received (in a simple text format, with one hash per line).
520 The operation will overwrite all user defined metadata, except if ``update`` is defined.
521 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.
523 To upload blocks of data to the container, set ``Content-Type`` to ``application/octet-stream`` and ``Content-Length`` to a valid value (except if using ``chunked`` as the ``Transfer-Encoding``).
525 ================ ===============================
526 Return Code Description
527 ================ ===============================
528 202 (Accepted) The request has been accepted
529 ================ ===============================
535 ====================== ===================================
536 Request Parameter Name Value
537 ====================== ===================================
538 until Optional timestamp
539 ====================== ===================================
541 If ``until`` is defined, the container is "purged" up to that time (the history of all objects up to then is deleted).
543 No reply content/headers.
545 ================ ===============================
546 Return Code Description
547 ================ ===============================
548 204 (No Content) The request succeeded
549 409 (Conflict) The container is not empty
550 ================ ===============================
558 ========= =================================
559 Operation Description
560 ========= =================================
561 HEAD Retrieve object metadata
563 PUT Write object data or copy/move object
566 POST Update object metadata/data
568 ========= =================================
574 ==================== ================================
575 Request Header Name Value
576 ==================== ================================
577 If-Match Retrieve if ETags match
578 If-None-Match Retrieve if ETags don't match
579 If-Modified-Since Retrieve if object has changed since provided timestamp
580 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
581 ==================== ================================
585 ====================== ===================================
586 Request Parameter Name Value
587 ====================== ===================================
588 version Optional version identifier
589 ====================== ===================================
593 ========================== ===============================
594 Reply Header Name Value
595 ========================== ===============================
596 ETag The ETag of the object
597 Content-Length The size of the object
598 Content-Type The MIME content type of the object
599 Last-Modified The last object modification date (regardless of version)
600 Content-Encoding The encoding of the object (optional)
601 Content-Disposition The presentation style of the object (optional)
602 X-Object-Version The object's version identifier
603 X-Object-Version-Timestamp The object's version timestamp
604 X-Object-Modified-By The user that comitted the object's version
605 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
606 X-Object-Sharing Object permissions (optional)
607 X-Object-Shared-By Object inheriting permissions (optional)
608 X-Object-Allowed-To Allowed actions on object (optional)
609 X-Object-Public Object's publicly accessible URI (optional)
610 X-Object-Meta-* Optional user defined metadata
611 ========================== ===============================
615 ================ ===============================
616 Return Code Description
617 ================ ===============================
618 200 (No Content) The request succeeded
619 ================ ===============================
625 ==================== ================================
626 Request Header Name Value
627 ==================== ================================
628 Range Optional range of data to retrieve
629 If-Range Retrieve the missing part if entity is unchanged; otherwise, retrieve the entire new entity (used together with Range header)
630 If-Match Retrieve if ETags match
631 If-None-Match Retrieve if ETags don't match
632 If-Modified-Since Retrieve if object has changed since provided timestamp
633 If-Unmodified-Since Retrieve if object has not changed since provided timestamp
634 ==================== ================================
638 ====================== ===================================
639 Request Parameter Name Value
640 ====================== ===================================
641 format Optional extended reply type (can be ``json`` or ``xml``)
642 hashmap Optional request for hashmap (no value parameter)
643 version Optional version identifier or ``list`` (specify a format if requesting a list)
644 ====================== ===================================
646 The reply is the object's data (or part of it), except if a hashmap is requested with ``hashmap``, or a version list with ``version=list`` (in both cases an extended reply format must be specified). Object headers (as in a ``HEAD`` request) are always included.
648 Hashmaps expose the underlying storage format of the object. Note that each hash is computed after trimming trailing null bytes of the corresponding block.
650 Example ``format=json`` reply:
654 {"block_hash": "sha1", "hashes": ["7295c41da03d7f916440b98e32c4a2a39351546c", ...], "block_size": 131072, "bytes": 242}
656 Example ``format=xml`` reply:
660 <?xml version="1.0" encoding="UTF-8"?>
661 <object name="file" bytes="24223726" block_size="131072" block_hash="sha1">
662 <hash>7295c41da03d7f916440b98e32c4a2a39351546c</hash>
666 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.
668 Example ``format=json`` reply:
672 {"versions": [[23, 1307700892], [28, 1307700898], ...]}
674 Example ``format=xml`` reply:
678 <?xml version="1.0" encoding="UTF-8"?>
680 <version timestamp="1307700892">23</version>
681 <version timestamp="1307700898">28</version>
682 <version timestamp="...">...</version>
685 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.
687 ========================== ===============================
688 Reply Header Name Value
689 ========================== ===============================
690 ETag The ETag of the object
691 Content-Length The size of the data returned
692 Content-Type The MIME content type of the object
693 Content-Range The range of data included (only on a single range request)
694 Last-Modified The last object modification date (regardless of version)
695 Content-Encoding The encoding of the object (optional)
696 Content-Disposition The presentation style of the object (optional)
697 X-Object-Version The object's version identifier
698 X-Object-Version-Timestamp The object's version timestamp
699 X-Object-Modified-By The user that comitted the object's version
700 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
701 X-Object-Sharing Object permissions (optional)
702 X-Object-Shared-By Object inheriting permissions (optional)
703 X-Object-Allowed-To Allowed actions on object (optional)
704 X-Object-Public Object's publicly accessible URI (optional)
705 X-Object-Meta-* Optional user defined metadata
706 ========================== ===============================
710 =========================== ==============================
711 Return Code Description
712 =========================== ==============================
713 200 (OK) The request succeeded
714 206 (Partial Content) The range request succeeded
715 304 (Not Modified) The object has not been modified
716 412 (Precondition Failed) The condition set can not be satisfied
717 416 (Range Not Satisfiable) The requested range is out of limits
718 =========================== ==============================
724 ==================== ================================
725 Request Header Name Value
726 ==================== ================================
727 If-Match Put if ETags match with current object
728 If-None-Match Put if ETags don't match with current object
729 ETag The MD5 hash of the object (optional to check written data)
730 Content-Length The size of the data written
731 Content-Type The MIME content type of the object
732 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
733 X-Copy-From The source path in the form ``/<container>/<object>``
734 X-Move-From The source path in the form ``/<container>/<object>``
735 X-Source-Account The source account to copy/move from
736 X-Source-Version The source version to copy from
737 Content-Encoding The encoding of the object (optional)
738 Content-Disposition The presentation style of the object (optional)
739 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
740 X-Object-Sharing Object permissions (optional)
741 X-Object-Public Object is publicly accessible (optional)
742 X-Object-Meta-* Optional user defined metadata
743 ==================== ================================
747 ====================== ===================================
748 Request Parameter Name Value
749 ====================== ===================================
750 format Optional extended request type (can be ``json`` or ``xml``)
751 hashmap Optional hashmap provided instead of data (no value parameter)
752 ====================== ===================================
754 The request is the object's data (or part of it), except if a hashmap is provided (using ``hashmap`` and ``format`` parameters). If using a hashmap 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 (in a simple text format, with one hash per line).
756 Hashmaps should be formatted as outlined in ``GET``.
758 ========================== ===============================
759 Reply Header Name Value
760 ========================== ===============================
761 ETag The MD5 hash of the object (on create)
762 X-Object-Version The object's new version
763 ========================== ===============================
765 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.
767 =========================== ==============================
768 Return Code Description
769 =========================== ==============================
770 201 (Created) The object has been created
771 409 (Conflict) The object can not be created from the provided hashmap, or there are conflicting permissions (a list of missing hashes, or a list of conflicting sharing paths will be included in the reply - in simple text format)
772 411 (Length Required) Missing ``Content-Length`` or ``Content-Type`` in the request
773 422 (Unprocessable Entity) The MD5 checksum of the data written to the storage system does not match the (optionally) supplied ETag value
774 =========================== ==============================
780 ==================== ================================
781 Request Header Name Value
782 ==================== ================================
783 If-Match Proceed if ETags match with object
784 If-None-Match Proceed if ETags don't match with object
785 Destination The destination path in the form ``/<container>/<object>``
786 Destination-Account The destination account to copy to
787 Content-Type The MIME content type of the object (optional)
788 Content-Encoding The encoding of the object (optional)
789 Content-Disposition The presentation style of the object (optional)
790 X-Source-Version The source version to copy from
791 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
792 X-Object-Sharing Object permissions (optional)
793 X-Object-Public Object is publicly accessible (optional)
794 X-Object-Meta-* Optional user defined metadata
795 ==================== ================================
797 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.
799 ========================== ===============================
800 Reply Header Name Value
801 ========================== ===============================
802 X-Object-Version The object's new version
803 ========================== ===============================
807 =========================== ==============================
808 Return Code Description
809 =========================== ==============================
810 201 (Created) The object has been created
811 409 (Conflict) There are conflicting permissions (a list of conflicting sharing paths will be included in the reply - in simple text format)
812 =========================== ==============================
818 Same as ``COPY``, without the ``X-Source-Version`` request header. The ``MOVE`` operation is always applied on the latest version.
824 ==================== ================================
825 Request Header Name Value
826 ==================== ================================
827 If-Match Proceed if ETags match with object
828 If-None-Match Proceed if ETags don't match with object
829 Content-Length The size of the data written (optional, to update)
830 Content-Type The MIME content type of the object (optional, to update)
831 Content-Range The range of data supplied (optional, to update)
832 Transfer-Encoding Set to ``chunked`` to specify incremental uploading (if used, ``Content-Length`` is ignored)
833 Content-Encoding The encoding of the object (optional)
834 Content-Disposition The presentation style of the object (optional)
835 X-Source-Object Update with data from the object at path ``/<container>/<object>`` (optional, to update)
836 X-Source-Account The source account to update from
837 X-Source-Version The source version to update from (optional, to update)
838 X-Object-Bytes The updated object's final size (optional, when updating)
839 X-Object-Manifest Object parts prefix in ``<container>/<object>`` form (optional)
840 X-Object-Sharing Object permissions (optional)
841 X-Object-Public Object is publicly accessible (optional)
842 X-Object-Meta-* Optional user defined metadata
843 ==================== ================================
847 ====================== ============================================
848 Request Parameter Name Value
849 ====================== ============================================
850 update Do not replace metadata (no value parameter)
851 ====================== ============================================
853 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.
855 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.
857 To update an object's data:
859 * 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.
860 * 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``).
861 * Set ``Content-Range`` as specified in RFC2616, with the following differences:
863 * Client software MAY omit ``last-byte-pos`` of if the length of the range being transferred is unknown or difficult to determine.
864 * Client software SHOULD not specify the ``instance-length`` (use a ``*``), unless there is a reason for performing a size check at the server.
865 * If ``Content-Range`` used has a ``byte-range-resp-spec = *``, data will be appended to the object.
867 Optionally, truncate the updated object to the desired length with the ``X-Object-Bytes`` header.
869 A data update will trigger an ETag change. Updated ETags correspond to the single Merkle hash of the object's hashmap (refer to http://bittorrent.org/beps/bep_0030.html for more information).
871 No reply content. No reply headers if only metadata is updated.
873 ========================== ===============================
874 Reply Header Name Value
875 ========================== ===============================
876 ETag The new ETag of the object (data updated)
877 X-Object-Version The object's new version
878 ========================== ===============================
882 =========================== ==============================
883 Return Code Description
884 =========================== ==============================
885 202 (Accepted) The request has been accepted (not a data update)
886 204 (No Content) The request succeeded (data updated)
887 409 (Conflict) There are conflicting permissions (a list of conflicting sharing paths will be included in the reply - in simple text format)
888 411 (Length Required) Missing ``Content-Length`` in the request
889 416 (Range Not Satisfiable) The supplied range is invalid
890 =========================== ==============================
892 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 an ``X-Object-Data`` field, as in the following example. The token is passed as a request parameter. ::
894 <form method="post" action="https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt?X-Auth-Token=0000" enctype="multipart/form-data">
895 <input type="file" name="X-Object-Data">
896 <input type="submit">
899 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 (usually, automatically handled by the browser). Metadata, sharing and other object attributes can not be set this way.
901 ========================== ===============================
902 Reply Header Name Value
903 ========================== ===============================
904 ETag The MD5 hash of the object
905 X-Object-Version The object's new version
906 ========================== ===============================
910 =========================== ==============================
911 Return Code Description
912 =========================== ==============================
913 201 (Created) The object has been created
914 =========================== ==============================
920 ====================== ===================================
921 Request Parameter Name Value
922 ====================== ===================================
923 until Optional timestamp
924 ====================== ===================================
926 If ``until`` is defined, the object is "purged" up to that time (the history up to then is deleted).
928 No reply content/headers.
930 =========================== ==============================
931 Return Code Description
932 =========================== ==============================
933 204 (No Content) The request succeeded
934 =========================== ==============================
936 Sharing and Public Objects
937 ^^^^^^^^^^^^^^^^^^^^^^^^^^
939 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.
941 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. The ``X-Object-Allowed-To`` header lists the actions allowed on an object, if it does not belong to the requesting user.
943 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):
945 ========================== ===============================
946 Reply Header Name Value
947 ========================== ===============================
948 ETag The ETag of the object
949 Content-Length The size of the data returned
950 Content-Type The MIME content type of the object
951 Content-Range The range of data included (only on a single range request)
952 Last-Modified The last object modification date (regardless of version)
953 Content-Encoding The encoding of the object (optional)
954 Content-Disposition The presentation style of the object (optional)
955 ========================== ===============================
957 Public objects are not included and do not influence cross-user listings. They are, however, readable by all users.
962 List of differences from the OOS API:
964 * Support for ``X-Account-Meta-*`` style headers at the account level. Use ``POST`` to update.
965 * Support for ``X-Container-Meta-*`` style headers at the container level. Can be set when creating via ``PUT``. Use ``POST`` to update.
966 * Header ``X-Container-Object-Meta`` at the container level and parameter ``meta`` in container listings. (**TBD**)
967 * Container policies to manage behavior and limits.
968 * Headers ``X-Container-Block-*`` at the container level, exposing the underlying storage characteristics.
969 * All metadata replies, at all levels, include latest modification information.
970 * At all levels, a ``HEAD`` or ``GET`` request may use ``If-Modified-Since`` and ``If-Unmodified-Since`` headers.
971 * 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.
972 * Option to include only shared containers/objects in listings.
973 * 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.
974 * Multi-range object ``GET`` support as outlined in RFC2616.
975 * Object hashmap retrieval through ``GET`` and the ``format`` parameter.
976 * Object create via hashmap through ``PUT`` and the ``format`` parameter.
977 * Object create using ``POST`` to support standard HTML forms.
978 * 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``. New ETag corresponds to the Merkle hash of the object's hashmap.
979 * Include new version identifier in replies for object replace/change requests.
980 * Object ``MOVE`` support.
981 * Conditional object create/update operations, using ``If-Match`` and ``If-None-Match`` headers.
982 * Time-variant account/container listings via the ``until`` parameter.
983 * Object versions - parameter ``version`` in ``HEAD``/``GET`` (list versions with ``GET``), ``X-Object-Version-*`` meta in replies, ``X-Source-Version`` in ``PUT``/``COPY``.
984 * Sharing/publishing with ``X-Object-Sharing``, ``X-Object-Public`` at the object level. Cross-user operations are allowed - controlled by sharing directives. Available actions in cross-user requests are reported with ``X-Object-Allowed-To``. Permissions may include groups defined with ``X-Account-Group-*`` at the account level. These apply to the object - not its versions.
985 * Support for prefix-based inheritance when enforcing permissions. Parent object carrying the authorization directives is reported in ``X-Object-Shared-By``.
986 * Copy and move between accounts with ``X-Source-Account`` and ``Destination-Account`` headers.
987 * Large object support with ``X-Object-Manifest``.
988 * Trace the user that created/modified an object with ``X-Object-Modified-By``.
989 * Purge container/object history with the ``until`` parameter in ``DELETE``.
991 Clarifications/suggestions:
993 * 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.
994 * 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.
995 * A ``GET`` reply for a level will include all headers of the corresponding ``HEAD`` request.
996 * 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.
997 * The ``Accept`` header may be used in requests instead of the ``format`` parameter to specify the desired request/reply format. The parameter overrides the header.
998 * Container/object lists use a ``200`` return code if the reply is of type json/xml. The reply will include an empty json/xml.
999 * 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.
1000 * 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.
1001 * A copy/move using ``PUT``/``COPY``/``MOVE`` will always update metadata, keeping all old values except the ones redefined in the request headers.
1002 * 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.
1010 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.
1012 Upon entrance to the service, a user is presented with the following elements - which can be represented as folders or with other related icons:
1014 * 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.
1015 * The ``trash`` element, which contains files that have been marked for deletion, but can still be recovered.
1016 * The ``shared`` element, which contains all objects shared by the user to other users of the system.
1017 * The ``others`` element, which contains all objects that other users share with the user.
1018 * 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.
1019 * The ``history`` element, which allows browsing past instances of ``home`` and - optionally - ``trash``.
1021 Objects in Pithos can be:
1023 * Moved to trash and then deleted.
1024 * Shared with specific permissions.
1025 * Made public (shared with non-Pithos users).
1026 * Restored from previous versions.
1028 Some of these functions are performed by the client software and some by the Pithos server.
1030 In the first version of Pithos, objects could also be assigned custom tags. This is no longer supported. Existing deployments can migrate tags into a specific metadata value, i.e. ``X-Object-Meta-Tags``.
1032 Implementation Guidelines
1033 ^^^^^^^^^^^^^^^^^^^^^^^^^
1035 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.
1037 Object names should use the ``/`` delimiter to impose a hierarchy of folders and files.
1039 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.
1041 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).
1043 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.
1045 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, 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``.
1047 Uploading and downloading data
1048 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1050 By using hashmaps to upload and download objects the corresponding operations can complete much faster.
1052 In the case of an upload, only the missing blocks will be submitted to the server:
1054 * Calculate the hash value for each block of the object to be uploaded. Use the hash algorithm and block size of the destination container.
1055 * Send a hashmap ``PUT`` request for the object.
1057 * Server responds with status ``201`` (Created):
1059 * Blocks are already on the server. The object has been created. Done.
1061 * Server responds with status ``409`` (Conflict):
1063 * Server's response body contains the hashes of the blocks that do not exist on the server.
1064 * For each hash value in the server's response (or all hashes together):
1066 * Send a ``POST`` request to the destination container with the corresponding data.
1068 * Repeat hashmap ``PUT``. Fail if the server's response is not ``201``.
1070 Consulting hashmaps when downloading allows for resuming partially transferred objects. The client should retrieve the hashmap from the server and compare it with the hashmap computed from the respective local file. Any missing parts can be downloaded with ``GET`` requests with the additional ``Range`` header.
1075 Consider the following algorithm for synchronizing a local folder with the server. The "state" is the complete object listing, with the corresponding attributes.
1079 L: local state (stored state from last sync with the server)
1080 C: current state (state computed right before sync)
1086 # No remote changes, nothing to do
1088 # Update local state to match that of the server
1091 # We have local changes
1093 # No remote changes, update the server
1097 # Both we and server have changes
1099 # We were lucky, we did the same change
1102 # We have conflicting changes
1107 * States represent file hashes (either MD5 or Merkle). Deleted or non-existing files are assumed to have a magic hash (e.g. empty string).
1108 * Updating a state (either local or remote) implies downloading, uploading or deleting the appropriate file.
1110 Recommended Practices and Examples
1111 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
1113 Assuming an authentication token is obtained, the following high-level operations are available - shown with ``curl``:
1115 * Get account information ::
1118 -H "X-Auth-Token: 0000" \
1119 https://pithos.dev.grnet.gr/v1/user
1121 * List available containers ::
1124 -H "X-Auth-Token: 0000" \
1125 https://pithos.dev.grnet.gr/v1/user
1127 * Get container information ::
1130 -H "X-Auth-Token: 0000" \
1131 https://pithos.dev.grnet.gr/v1/user/pithos
1133 * Add a new container ::
1136 -H "X-Auth-Token: 0000" \
1137 https://pithos.dev.grnet.gr/v1/user/test
1139 * Delete a container ::
1141 curl -X DELETE -D - \
1142 -H "X-Auth-Token: 0000" \
1143 https://pithos.dev.grnet.gr/v1/user/test
1145 * List objects in a container ::
1148 -H "X-Auth-Token: 0000" \
1149 https://pithos.dev.grnet.gr/v1/user/pithos
1151 * List objects in a container (extended reply) ::
1154 -H "X-Auth-Token: 0000" \
1155 https://pithos.dev.grnet.gr/v1/user/pithos?format=json
1157 It is recommended that extended replies are cached and subsequent requests utilize the ``If-Modified-Since`` header.
1159 * List metadata keys used by objects in a container
1161 Will be in the ``X-Container-Object-Meta`` reply header, included in container information or object list (``HEAD`` or ``GET``). (**TBD**)
1163 * List objects in a container having a specific meta defined ::
1166 -H "X-Auth-Token: 0000" \
1167 https://pithos.dev.grnet.gr/v1/user/pithos?meta=favorites
1169 * Retrieve an object ::
1172 -H "X-Auth-Token: 0000" \
1173 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1175 * Retrieve an object (specific ranges of data) ::
1178 -H "X-Auth-Token: 0000" \
1179 -H "Range: bytes=0-9" \
1180 https://pithos.dev.grnet.gr/v1/user/pithos/README.txt
1182 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``.
1184 * Add a new object (folder type) (**TBD**) ::
1187 -H "X-Auth-Token: 0000" \
1188 -H "Content-Type: application/folder" \
1189 https://pithos.dev.grnet.gr/v1/user/pithos/folder
1191 * Add a new object ::
1194 -H "X-Auth-Token: 0000" \
1195 -H "Content-Type: text/plain" \
1197 https://pithos.dev.grnet.gr/v1/user/pithos/folder/EXAMPLE.txt
1199 * Update an object ::
1202 -H "X-Auth-Token: 0000" \
1203 -H "Content-Length: 10" \
1204 -H "Content-Type: application/octet-stream" \
1205 -H "Content-Range: bytes 10-19/*" \
1207 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1209 This will update bytes 10-19 with the data specified.
1211 * Update an object (append) ::
1214 -H "X-Auth-Token: 0000" \
1215 -H "Content-Length: 10" \
1216 -H "Content-Type: application/octet-stream" \
1217 -H "Content-Range: bytes */*" \
1219 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1221 * Update an object (truncate) ::
1224 -H "X-Auth-Token: 0000" \
1225 -H "X-Source-Object: /folder/EXAMPLE.txt" \
1226 -H "Content-Range: bytes 0-0/*" \
1227 -H "X-Object-Bytes: 0" \
1228 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1230 This will truncate the object to 0 bytes.
1232 * Add object metadata ::
1235 -H "X-Auth-Token: 0000" \
1236 -H "X-Object-Meta-First: first_meta_value" \
1237 -H "X-Object-Meta-Second: second_meta_value" \
1238 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1240 * Delete object metadata ::
1243 -H "X-Auth-Token: 0000" \
1244 -H "X-Object-Meta-First: first_meta_value" \
1245 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
1247 Metadata can only be "set". To delete ``X-Object-Meta-Second``, reset all metadata.
1249 * Delete an object ::
1251 curl -X DELETE -D - \
1252 -H "X-Auth-Token: 0000" \
1253 https://pithos.dev.grnet.gr/v1/user/folder/EXAMPLE.txt
projects / pithos / blob