29c10db0cb
ssync currently does the wrong thing when replicating object dirs
containing both a .data and a .meta file. The ssync sender uses a
single PUT to send both object content and metadata to the receiver,
using the metadata (.meta file) timestamp. This results in the object
content timestamp being advanced to the metadata timestamp,
potentially overwriting newer object data on the receiver and causing
an inconsistency with the container server record for the object.
For example, replicating an object dir with {t0.data(etag=x), t2.meta}
to a receiver with t1.data(etag=y) will result in the creation of
t2.data(etag=x) on the receiver. However, the container server will
continue to list the object as t1(etag=y).
This patch modifies ssync to replicate the content of .data and .meta
separately using a PUT request for the data (no change) and a POST
request for the metadata. In effect, ssync replication replicates the
client operations that generated the .data and .meta files so that
the result of replication is the same as if the original client requests
had persisted on all object servers.
Apart from maintaining correct timestamps across sync'd nodes, this has
the added benefit of not needing to PUT objects when only the metadata
has changed and a POST will suffice.
Taking the same example, ssync sender will no longer PUT t0.data but will
POST t2.meta resulting in the receiver having t1.data and t2.meta.
The changes are backwards compatible: an upgraded sender will only sync
data files to a legacy receiver and will not sync meta files (fixing the
erroneous behavior described above); a legacy sender will operate as
before when sync'ing to an upgraded receiver.
Changes:
- diskfile API provides methods to get the data file timestamp
as distinct from the diskfile timestamp.
- diskfile yield_hashes return tuple now passes a dict mapping data and
meta (if any) timestamps to their respective values in the timestamp
field.
- ssync_sender will encode data and meta timestamps in the
(hash_path, timestamp) tuple sent to the receiver during
missing_checks.
- ssync_receiver compares sender's data and meta timestamps to any
local diskfile and may specify that only data or meta parts are sent
during updates phase by appending a qualifier to the hash returned
in its 'wanted' list.
- ssync_sender now sends POST subrequests when a meta file
exists and its content needs to be replicated.
- ssync_sender may send *only* a POST if the receiver indicates that
is the only part required to be sync'd.
- object server will allow PUT and DELETE with earlier timestamp than
a POST
- Fixed TODO related to replicated objects with fast-POST and ssync
Related spec change-id: I60688efc3df692d3a39557114dca8c5490f7837e
Co-Authored-By: Clay Gerrard <clay.gerrard@gmail.com>
Closes-Bug: 1501528
Change-Id: I97552d194e5cc342b0a3f4b9800de8aa6b9cb85b
|
||
|---|---|---|
| bin | ||
| doc | ||
| etc | ||
| examples | ||
| swift | ||
| test | ||
| .coveragerc | ||
| .functests | ||
| .gitignore | ||
| .gitreview | ||
| .mailmap | ||
| .probetests | ||
| .unittests | ||
| AUTHORS | ||
| babel.cfg | ||
| bandit.yaml | ||
| CHANGELOG | ||
| CONTRIBUTING.md | ||
| LICENSE | ||
| MANIFEST.in | ||
| README.md | ||
| requirements.txt | ||
| setup.cfg | ||
| setup.py | ||
| test-requirements.txt | ||
| tox.ini | ||
Swift
A distributed object storage system designed to scale from a single machine to thousands of servers. Swift is optimized for multi-tenancy and high concurrency. Swift is ideal for backups, web and mobile content, and any other unstructured data that can grow without bound.
Swift provides a simple, REST-based API fully documented at http://docs.openstack.org/.
Swift was originally developed as the basis for Rackspace's Cloud Files and was open-sourced in 2010 as part of the OpenStack project. It has since grown to include contributions from many companies and has spawned a thriving ecosystem of 3rd party tools. Swift's contributors are listed in the AUTHORS file.
Docs
To build documentation install sphinx (pip install sphinx), run
python setup.py build_sphinx, and then browse to /doc/build/html/index.html.
These docs are auto-generated after every commit and available online at
http://docs.openstack.org/developer/swift/.
For Developers
The best place to get started is the "SAIO - Swift All In One". This document will walk you through setting up a development cluster of Swift in a VM. The SAIO environment is ideal for running small-scale tests against swift and trying out new features and bug fixes.
You can run unit tests with .unittests and functional tests with
.functests.
If you would like to start contributing, check out these notes to help you get started.
Code Organization
- bin/: Executable scripts that are the processes run by the deployer
- doc/: Documentation
- etc/: Sample config files
- swift/: Core code
- account/: account server
- common/: code shared by different modules
- middleware/: "standard", officially-supported middleware
- ring/: code implementing Swift's ring
- container/: container server
- obj/: object server
- proxy/: proxy server
- test/: Unit and functional tests
Data Flow
Swift is a WSGI application and uses eventlet's WSGI server. After the
processes are running, the entry point for new requests is the Application
class in swift/proxy/server.py. From there, a controller is chosen, and the
request is processed. The proxy may choose to forward the request to a back-
end server. For example, the entry point for requests to the object server is
the ObjectController class in swift/obj/server.py.
For Deployers
Deployer docs are also available at http://docs.openstack.org/developer/swift/. A good starting point is at http://docs.openstack.org/developer/swift/deployment_guide.html
You can run functional tests against a swift cluster with .functests. These
functional tests require /etc/swift/test.conf to run. A sample config file
can be found in this source tree in test/sample.conf.
For Client Apps
For client applications, official Python language bindings are provided at http://github.com/openstack/python-swiftclient.
Complete API documentation at http://docs.openstack.org/api/openstack-object-storage/1.0/content/
For more information come hang out in #openstack-swift on freenode.
Thanks,
The Swift Development Team