3f943cfcf2
At PUT object request, proxy server makes backend headers (e.g.
X-Container-Partition) which help object-servers to determine
the container-server they should update. In addition, the backend
headers are created as many as the number of container replicas.
(i.e. 3 replica in container ring, 3 backend headers will be created)
On EC case, Swift fans out fragment archives to backend object-servers.
Basically the number of fragment archives will be more than the container
replica number and proxy-server assumes a request as success when quorum
number of object-server succeeded to store. That would cause to make an
orphaned object which is stored but not container updated.
For example, assuming k=10, m=4, container replica=3 case:
Assuming, proxy-server attempts to make 14 backend streams but
unfortunately first 3 nodes returns 507 (disk failure) and then
the Swift doesn't have any other disks.
In the case, proxy keeps 11 backend streams to store and current Swift
assumes it as sufficient because it is more than or equals quorum (right
now k+1 is sufficient i.e. 11 backend streams are enough to store)
However, in the case, the 11 streams doesn't have the container update
header so that the request will succeed but container will be never updated.
This patch allows to extract container updates up to object quorum_size
+ 1 to more nodes to ensure the updates. This approach sacrifices the
container update cost a bit because duplicated updates will be there but
quorum sizes + 1 seems reasonable (even if it's reaplicated case) to pay
to ensure that instead of whole objects incude the update headers.
Now Swift will work like as follows:
For example:
k=10, m=4, qurum_size=11 (k+1), 3 replica for container.
CU: container update
CA: commit ack
That result in like as
CU CU CU CU CU CU CU CU CU CU CU CU
[507, 507, 507, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201, 201]
CA CA CA CA CA
In this case, at least 3 container updates are saved.
For another example:
7 replicated objects, qurum_size=4 (7//2+1), 3 replica for container.
CU: container update
CA: commit ack (201s for successful PUT on replicated)
CU CU CU CU CU
[507, 507, 507, 201, 201, 201, 201]
CA CA CA CA
In this replicated case, at least 2 container updates are saved.
Cleaned up some unit tests so that modifying policies doesn't leak
between tests.
Co-Authored-By: John Dickinson <me@not.mn>
Co-Authored-By: Sam Merritt <sam@swiftstack.com>
Closes-Bug: #1460920
Change-Id: I04132858f44b42ee7ecf3b7994cb22a19d001d70
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