openstack/swift
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swift/doc/source/development_ondisk_backends.rst

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DiskFile API, with reference implementation Refactor on-disk knowledge out of the object server by pushing the async update pickle creation to the new DiskFileManager class (name is not the best, so suggestions welcome), along with the REPLICATOR method logic. We also move the mount checking and thread pool storage to the new ondisk.Devices object, which then also becomes the new home of the audit_location_generator method. For the object server, a new setup() method is now called at the end of the controller's construction, and the _diskfile() method has been renamed to get_diskfile(), to allow implementation specific behavior. We then hide the need for the REST API layer to know how and where quarantining needs to be performed. There are now two places it is checked internally, on open() where we verify the content-length, name, and x-timestamp metadata, and in the reader on close where the etag metadata is checked if the entire file was read. We add a reader class to allow implementations to isolate the WSGI handling code for that specific environment (it is used no-where else in the REST APIs). This simplifies the caller's code to just use a "with" statement once open to avoid multiple points where close needs to be called. For a full historical comparison, including the usage patterns see: https://gist.github.com/portante/5488238 (as of master, 2b639f5, Merge "Fix 500 from account-quota This Commit middleware") --------------------------------+------------------------------------ DiskFileManager(conf) Methods: .pickle_async_update() .get_diskfile() .get_hashes() Attributes: .devices .logger .disk_chunk_size .keep_cache_size .bytes_per_sync DiskFile(a,c,o,keep_data_fp=) DiskFile(a,c,o) Methods: Methods: *.__iter__() .close(verify_file=) .is_deleted() .is_expired() .quarantine() .get_data_file_size() .open() .read_metadata() .create() .create() .write_metadata() .delete() .delete() Attributes: Attributes: .quarantined_dir .keep_cache .metadata *DiskFileReader() Methods: .__iter__() .close() Attributes: +.was_quarantined DiskWriter() DiskFileWriter() Methods: Methods: .write() .write() .put() .put() * Note that the DiskFile class * Note that the DiskReader() object implements all the methods returned by the necessary for a WSGI app DiskFileOpened.reader() method iterator implements all the methods necessary for a WSGI app iterator + Note that if the auditor is refactored to not use the DiskFile class, see https://review.openstack.org/44787 then we don't need the was_quarantined attribute A reference "in-memory" object server implementation of a backend DiskFile class in swift/obj/mem_server.py and swift/obj/mem_diskfile.py. One can also reference https://github.com/portante/gluster-swift/commits/diskfile for the proposed integration with the gluster-swift code based on these changes. Change-Id: I44e153fdb405a5743e9c05349008f94136764916 Signed-off-by: Peter Portante <peter.portante@redhat.com>
2013-09-12 19:51:18 -04:00
===============================
Pluggable On-Disk Back-end APIs
===============================
The internal REST API used between the proxy server and the account, container
and object server is almost identical to public Swift REST API, but with a few
internal extentsions (for example, update an account with a new container).
The pluggable back-end APIs for the three REST API servers (account,
container, object) abstracts the needs for servicing the various REST APIs
from the details of how data is laid out and stored on-disk.
The APIs are documented in the reference implementations for all three
servers. For historical reasons, the object server backend reference
implementation module is named `diskfile`, while the account and container
server backend reference implementation modules are named appropriately.
-----------------------------------------
Back-end API for Account Server REST APIs
-----------------------------------------
.. automodule:: swift.account.backend
:noindex:
:members:
-------------------------------------------
Back-end API for Container Server REST APIs
-------------------------------------------
.. automodule:: swift.container.backend
:noindex:
:members:
----------------------------------------
Back-end API for Object Server REST APIs
----------------------------------------
.. automodule:: swift.obj.diskfile
:noindex:
:members:
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