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In the ring builder, we place partitions with maximum possible dispersion across tiers, where a "tier" is region, then zone, then IP/port,then device. Now, instead of IP/port, just use IP. The port wasn't really getting us anything; two different object servers on two different ports on one machine aren't separate failure domains. However, if someone has only a few machines and is using one object server on its own port per disk, then the ring builder would end up with every disk in its own IP/port tier, resulting in bad (with respect to durability) partition placement. For example: assume 1 region, 1 zone, 4 machines, 48 total disks (12 per machine), and one object server (and hence one port) per disk. With the old behavior, partition replicas will all go in the one region, then the one zone, then pick one of 48 IP/port pairs, then pick the one disk therein. This gives the same result as randomly picking 3 disks (without replacement) to store data on; it completely ignores machine boundaries. With the new behavior, the replica placer will pick the one region, then the one zone, then one of 4 IPs, then one of 12 disks therein. This gives the optimal placement with respect to durability. The same applies to Ring.get_more_nodes(). Co-Authored-By: Kota Tsuyuzaki <tsuyuzaki.kota@lab.ntt.co.jp> Change-Id: Ibbd740c51296b7e360845b5309d276d7383a3742
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