a7da223262
There is an intermittent failure in the test_part_swapping_problem
test found in test/unit/common/ring/test_builder.py.
The test does a rebalance, then changes the ring to test a specific
problem, does some housekeeping and then rebalances again. The problem
is the ringbuilder keeps track of where in the ring it started the
last ring rebalance, saved in `_last_part_gather_start`.
On a rebalance, or more specifically in `_gather_parts_for_balance` we
then we will start somewhere on the other side of the ring with:
quarter_turn = (self.parts // 4)
random_half = random.randint(0, self.parts / 2)
start = (self._last_part_gather_start + quarter_turn +
random_half) % self.parts
Because we don't reset `_last_part_gather_start` when we change the ring
in the test, there is edge case where if we are unlucky during both
rebalances whereby both calls to randint returns a relatively large
number pushes the start of the second rebalance to the wrong side
of the ring. Actually it's more problematic, and only 1 large random
and a one in the middle will cause it, maybe pictures help:
rabalance 1 (r1): quarter_turn = 4, random_half = 5
rebalance 2 (r2): quarter_turn = 4, random_half = 3
r1 r2
| |
v v
array('H', [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1]),
array('H', [1, 1, 1, 1, 2, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 3]),
array('H', [2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4])]
Now when gathering for rebalance 2 it'll pick:
array('H', [0, 0, 0, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, X]),
array('H', [X, X, 1, 1, 2, 2, 2, 3, 3, 3, 2, 2, 2, 3, 3, 3]),
array('H', [2, 2, 2, 2, 3, 3, 4, 4, 4, 4, 3, 4, 4, 4, 4, 4])]
Which can cause the 3 attempts to gather and rebalance to be used up.
This causes the intermittent failure seen in the bug.
This patch solves this by resetting `_gather_parts_for_balance` to 0
while we tidy up the ring change. Meaning we'll always start on the
correct side of the ring.
Change-Id: I0d3a69620d4734091dfa516efd0d6b2ed87e196b
Closes-Bug: #1724356
Team and repository tags
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 https://docs.openstack.org/swift/latest/.
For Developers
Getting Started
Swift is part of OpenStack and follows the code contribution, review, and testing processes common to all OpenStack projects.
If you would like to start contributing, check out these notes to help you get started.
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.
Tests
There are three types of tests included in Swift's source tree.
- Unit tests
- Functional tests
- Probe tests
Unit tests check that small sections of the code behave properly. For example, a unit test may test a single function to ensure that various input gives the expected output. This validates that the code is correct and regressions are not introduced.
Functional tests check that the client API is working as expected. These can be run against any endpoint claiming to support the Swift API (although some tests require multiple accounts with different privilege levels). These are "black box" tests that ensure that client apps written against Swift will continue to work.
Probe tests are "white box" tests that validate the internal workings of a Swift cluster. They are written to work against the "SAIO - Swift All In One" dev environment. For example, a probe test may create an object, delete one replica, and ensure that the background consistency processes find and correct the error.
You can run unit tests with .unittests, functional tests
with .functests, and probe tests with
.probetests. There is an additional .alltests
script that wraps the other three.
To fully run the tests, the target environment must use a filesystem
that supports large xattrs. XFS is strongly recommended. For unit tests
and in-process functional tests, either mount /tmp with XFS
or provide another XFS filesystem via the TMPDIR
environment variable. Without this setting, tests should still pass, but
a very large number will be skipped.
Code Organization
- bin/: Executable scripts that are the processes run by the deployer
- doc/: Documentation
- etc/: Sample config files
- examples/: Config snippets used in the docs
- swift/: Core code
- account/: account server
- cli/: code that backs some of the CLI tools in bin/
- common/: code shared by different modules
- middleware/: "standard", officially-supported middleware
- ring/: code implementing Swift's ring
- container/: container server
- locale/: internationalization (translation) data
- obj/: object server
- proxy/: proxy server
- test/: Unit, functional, and probe 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 https://docs.openstack.org/swift/latest/. A good starting point is at https://docs.openstack.org/swift/latest/deployment_guide.html There is an ops runbook that gives information about how to diagnose and troubleshoot common issues when running a Swift cluster.
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 https://developer.openstack.org/api-ref/object-store/
There is a large ecosystem of applications and libraries that support and work with OpenStack Swift. Several are listed on the associated projects page.
For more information come hang out in #openstack-swift on freenode.
Thanks,
The Swift Development Team