2d55960a22
Consider two replicas of the same object whose ondisk files
have diverged due to failures:
A has t2.ts
B has t1.data, t4.meta
(The DELETE at t2 did not make it to B. The POST at t4 was
rejected by A.)
After ssync replication the two ondisk file sets will not be
consistent:
A has t2.ts (ssync cannot POST t4.meta to this node)
B has t2.ts, t4.meta (ssync should not delete t4.meta,
there may be a t3.data somewhere)
Consequenty the two nodes will report different hashes for the
object's suffix, and replication will repeat, always with the
inconsistent outcome. This scenario is reproduced by the probe
test added in this patch.
(Note that rsync replication does result in (t2.ts, t4.meta)
on both nodes.)
The solution is to change the way that suffix hashes are
calculated. Currently the names of *all* files found in each
object dir are added to the hash. With this patch the
timestamps of only those files that could be used to
construct a valid diskfile are added to the hash. File
extensions are appended to the timestamp so that in most
'normal' situations the result of the hashing is the same
as before this patch. That avoids a storm of hash mismatches
when this patch is deployed in an existing cluster.
In the problem case described above, t4.meta is no longer
added to the hash, since it is not useful for constructing
a diskfile. (Note that t4.meta is not deleted because it
may become useful should a t3.data be replicated in future).
Closes-Bug: 1534276
Change-Id: I99e88b8d5f5d9bc22b42112a99634ba942415e05
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