a0fcca1e05
SSYNC is designed to limit concurrent incoming connections in order to prevent IO contention. The reconstructor should expect remote replication servers to fail ssync_sender when the remote is too busy. When the remote rejects SSYNC - it should avoid forcing additional IO against the remote with a REPLICATE request which causes suffix rehashing. Suffix rehashing via REPLICATE verbs takes two forms: 1) a initial pre-flight call to REPLICATE /dev/part will cause a remote primary to rehash any invalid suffixes and return a map for the local sender to compare so that a sync can be performed on any mis-matched suffixes. 2) a final call to REPLICATE /dev/part/suf1-suf2-suf3[-sufX[...]] will cause the remote primary to rehash the *given* suffixes even if they are *not* invalid. This is a requirement for rsync replication because after a suffix is synced via rsync the contents of a suffix dir will likely have changed and the remote server needs to update it hashes.pkl to reflect the new data. SSYNC does not *need* to send a post-sync REPLICATE request. Any suffixes that are modified by the SSYNC protocol will call _finalize_put under the hood as it is syncing. It is however not harmful and potentially useful to go ahead refresh hashes after an SSYNC while the inodes of those suffixes are warm in the cache. However, that only makes sense if the SSYNC conversation actually synced any suffixes - if SSYNC is rejected for concurrency before it ever got started there is no value in the remote performing a rehash. It may be that *another* reconstructor is pushing data into that same partition and the suffixes will become immediately invalidated. If a ssync_sender does not successful finish a sync the reconstructor should skip the REPLICATE call entirely and move on to the next partition without causing any useless remote IO. Closes-Bug: #1665141 Change-Id: Ia72c407247e4525ef071a1728750850807ae8231
Team and repository tags
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
Getting Started
Swift is part of OpenStack and follows the code contribution, review, and testing processes common to all OpenStack projects.
If you would like to start contributing, check out these notes to help you get started.
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.
Tests
There are three types of tests included in Swift's source tree.
- Unit tests
- Functional tests
- Probe tests
Unit tests check that small sections of the code behave properly. For example, a unit test may test a single function to ensure that various input gives the expected output. This validates that the code is correct and regressions are not introduced.
Functional tests check that the client API is working as expected. These can be run against any endpoint claiming to support the Swift API (although some tests require multiple accounts with different privilege levels). These are "black box" tests that ensure that client apps written against Swift will continue to work.
Probe tests are "white box" tests that validate the internal workings of a Swift cluster. They are written to work against the "SAIO - Swift All In One" dev environment. For example, a probe test may create an object, delete one replica, and ensure that the background consistency processes find and correct the error.
You can run unit tests with .unittests, functional tests
with .functests, and probe tests with
.probetests. There is an additional .alltests
script that wraps the other three.
Code Organization
- bin/: Executable scripts that are the processes run by the deployer
- doc/: Documentation
- etc/: Sample config files
- examples/: Config snippets used in the docs
- swift/: Core code
- account/: account server
- cli/: code that backs some of the CLI tools in bin/
- common/: code shared by different modules
- middleware/: "standard", officially-supported middleware
- ring/: code implementing Swift's ring
- container/: container server
- locale/: internationalization (translation) data
- obj/: object server
- proxy/: proxy server
- test/: Unit, functional, and probe 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
There is an ops runbook that gives information about how to diagnose and troubleshoot common issues when running a Swift cluster.
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/
There is a large ecosystem of applications and libraries that support and work with OpenStack Swift. Several are listed on the associated projects page.
For more information come hang out in #openstack-swift on freenode.
Thanks,
The Swift Development Team