How are tests parallelized, how do they know the number of threads they can run on?

jamesf...@gmail.com

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Apr 9, 2015, 11:48:56 PM4/9/15

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How are tests parallelized, how do they know the number of threads they can run on?

Thanks,
James

Damien Martin-guillerez

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Apr 10, 2015, 2:49:02 AM4/10/15

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CC +Philipp Wollermann +Ulf Adams

Tests can be sharded by setting the shard_count attribute. Each shard would run in a separate thread. //src/test/shell/bazel:base_workspace_test is supposed to have shard_count set to 3 (src/test/shell/unitbash.sh selects the test to run depending on the shard number). However, there is a bug in shell test sharding for now, I have got time to fix it now.

For JUnit tests (Philip and Ulf knows that better), I believe the sharding support should Just Work if you set the shard_count attribute but I doubt we did test it in Bazel.

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Philipp Wollermann

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Apr 10, 2015, 3:04:09 AM4/10/15

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AFAIK test sharding for JUnit tests will not work in Bazel yet, as we haven't open-sourced our full-featured JUnit test runner yet. I'm on that right now :)

Cheers,

Philipp

Han-Wen Nienhuys

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Apr 10, 2015, 4:01:51 AM4/10/15

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As Damien and Philipp mentioned, we start up N copies of the test, and
each copy runs a different set of tests. This needs support from the
language specific test runners, and may have bugs.

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