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Example: $ swift-ring-builder account.builder set_replicas 4 $ swift-ring-builder rebalance This is a prerequisite for supporting globally-distributed clusters, as operators of such clusters will probably want at least as many replicas as they have regions. Therefore, adding a region requires adding a replica. Similarly, removing a region lets an operator remove a replica and save some money on disks. In order to not hose clusters with lots of data, swift-ring-builder now allows for setting of fractional replicas. Thus, one can gradually increase the replica count at a rate that does not adversely affect cluster performance. Example: $ swift-ring-builder object.builder set_replicas 3.01 $ swift-ring-builder object.builder rebalance <distribute rings and wait> $ swift-ring-builder object.builder set_replicas 3.02 $ swift-ring-builder object.builder rebalance <distribute rings and wait>... Obviously, fractional replicas are nonsensical for a single partition. A fractional replica count is for the whole ring, not for any individual partition, and indicates the average number of replicas of each partition. For example, a replica count of 3.2 means that 20% of partitions have 4 replicas and 80% have 3 replicas. Changes do not take effect until after the ring is rebalanced. Thus, if you mean to go from 3 replicas to 3.01 but you accidentally type 2.01, no data is lost. Additionally, 'swift-ring-builder X.builder create' can now take a decimal argument for the number of replicas. DocImpact Change-Id: I12b34dacf60350a297a46be493d5d171580243ff
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://doc.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.
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