b491549ac2
Without a (per-disk) threadpool, requests to a slow disk would affect all clients by blocking the entire eventlet reactor on read/write/etc. The slower the disk, the worse the performance. On an object server, you frequently have at least one slow disk due to auditing and replication activity sucking up all the available IO. By kicking those blocking calls out to a separate OS thread, we let the eventlet reactor make progress in other greenthreads, and by having a per-disk pool, we ensure that one slow disk can't suck up all the resources of an entire object server. There were a few blocking calls that were done with eventlet.tpool, but that's a fixed-size global threadpool, so I moved them to the per-disk threadpools. If the object server is configured not to use per-disk threadpools, (i.e. threads_per_disk = 0, which is the default), those call sites will still ultimately end up using eventlet.tpool.execute. You won't end up blocking a whole object server while waiting for a huge fsync. If you decide not to use threadpools, the only extra overhead should be a few extra Python function calls here and there. This is accomplished by setting threads_per_disk = 0 in the config. blueprint concurrent-disk-io Change-Id: I490f8753d926fdcee3a0c65c5aaf715bc2b7c290
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