a80c720af5
For this commit, ssync is just a direct replacement for how
we use rsync. Assuming we switch over to ssync completely
someday and drop rsync, we will then be able to improve the
algorithms even further (removing local objects as we
successfully transfer each one rather than waiting for whole
partitions, using an index.db with hash-trees, etc., etc.)
For easier review, this commit can be thought of in distinct
parts:
1) New global_conf_callback functionality for allowing
services to perform setup code before workers, etc. are
launched. (This is then used by ssync in the object
server to create a cross-worker semaphore to restrict
concurrent incoming replication.)
2) A bit of shifting of items up from object server and
replicator to diskfile or DEFAULT conf sections for
better sharing of the same settings. conn_timeout,
node_timeout, client_timeout, network_chunk_size,
disk_chunk_size.
3) Modifications to the object server and replicator to
optionally use ssync in place of rsync. This is done in
a generic enough way that switching to FutureSync should
be easy someday.
4) The biggest part, and (at least for now) completely
optional part, are the new ssync_sender and
ssync_receiver files. Nice and isolated for easier
testing and visibility into test coverage, etc.
All the usual logging, statsd, recon, etc. instrumentation
is still there when using ssync, just as it is when using
rsync.
Beyond the essential error and exceptional condition
logging, I have not added any additional instrumentation at
this time. Unless there is something someone finds super
pressing to have added to the logging, I think such
additions would be better as separate change reviews.
FOR NOW, IT IS NOT RECOMMENDED TO USE SSYNC ON PRODUCTION
CLUSTERS. Some of us will be in a limited fashion to look
for any subtle issues, tuning, etc. but generally ssync is
an experimental feature. In its current implementation it is
probably going to be a bit slower than rsync, but if all
goes according to plan it will end up much faster.
There are no comparisions yet between ssync and rsync other
than some raw virtual machine testing I've done to show it
should compete well enough once we can put it in use in the
real world.
If you Tweet, Google+, or whatever, be sure to indicate it's
experimental. It'd be best to keep it out of deployment
guides, howtos, etc. until we all figure out if we like it,
find it to be stable, etc.
Change-Id: If003dcc6f4109e2d2a42f4873a0779110fff16d6
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.
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