test-queue

test-queue

Yet another parallel test runner, built using a centralized queue to ensure optimal distribution of tests between workers.

Specifically optimized for CI environments: build statistics from each run are stored locally and used to sort the queue at the beginning of the next run.

Usage

test-queue bundles testunit-queue, minitest-queue, and rspec-queue binaries which can be used directly:

$ minitest-queue $(find test/ -name \*_test.rb)
$ rspec-queue --format progress spec

But the underlying TestQueue::Runner::TestUnit, TestQueue::Runner::Minitest, and TestQueue::Runner::RSpec are built to be subclassed by your application. I recommend checking a new executable into your project using one of these superclasses.

$ vim script/test-queue
$ chmod +x script/test-queue
$ git add script/test-queue

Since test-queue uses fork(2) to spawn off workers, you must ensure each worker runs in an isolated environment. Use the after_fork hook with a custom runner to reset any global state.

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Environment variables

• TEST_QUEUE_WORKERS: Number of workers to use per master (default: all available cores)
• TEST_QUEUE_VERBOSE: Show results as they are available (default: 0)
• TEST_QUEUE_SOCKET: Unix socket path (or TCP address:port pair) used for communication (default: /tmp/test_queue_XXXXX.sock)
• TEST_QUEUE_RELAY: Relay results back to a central master, specified as TCP address:port
• TEST_QUEUE_STATS: path to cache build stats in-build CI runs (default: .test_queue_stats)
• TEST_QUEUE_FORCE: Comma separated list of suites to run
• TEST_QUEUE_RELAY_TIMEOUT: When using distributed builds, the amount of time a remote master will try to reconnect to start work
• TEST_QUEUE_RELAY_TOKEN: When using distributed builds, this must be the same on remote masters and the central master for remote masters to be able to connect.
• TEST_QUEUE_REMOTE_MASTER_MESSAGE: When using distributed builds, set this on a remote master and it will appear in that master's connection message on the central master.
• TEST_QUEUE_SPLIT_GROUPS: Split tests up by example rather than example group. Faster for tests with short setup time such as selenium. RSpec only. Add the :no_split tag to ExampleGroups you don't want split.

Design

test-queue uses a simple master + pre-fork worker model. The master exposes a Unix domain socket server which workers use to grab tests off the queue.

─┬─ 21232 minitest-queue master
 ├─── 21571 minitest-queue worker [3] - AuthenticationTest
 ├─── 21568 minitest-queue worker [2] - ApiTest
 ├─── 21565 minitest-queue worker [1] - UsersControllerTest
 └─── 21562 minitest-queue worker [0] - UserTest

test-queue also has a distributed mode, where additional masters can share the workload and relay results back to a central master.

Distributed mode

To use distributed mode, the central master must listen on a TCP port. Additional masters can be booted in relay mode to connect to the central master. Remote masters must provide a TEST_QUEUE_RELAY_TOKEN to match the central master's.

$ TEST_QUEUE_RELAY_TOKEN=123 TEST_QUEUE_SOCKET=0.0.0.0:12345 bundle exec minitest-queue ./test/example_test.rb
$ TEST_QUEUE_RELAY_TOKEN=123 TEST_QUEUE_RELAY=0.0.0.0:12345  bundle exec minitest-queue ./test/example_test.rb
$ TEST_QUEUE_RELAY_TOKEN=123 ./test-multi.sh

See the Parameterized Trigger Plugin for a simple way to do this with Jenkins.

See also

• https://github.com/Shopify/rails_parallel
• https://github.com/grosser/parallel_tests