chore: add worker build on CI
Summary
From #7610. @rickhanlonii could you take a look? 🙂
Test plan
Will fail (for now)
worker_threads is unflagged in node 11.7.0, so the extra job isn't necessary. When (if) we land #7681 I'll update this PR to remove all the disableWorkerThreads: true and see where we're at
Circle has node 11.8 now, which has the umask fix. Rebased, hopefully a better result this time 🙂
We test threads but we're actually running our test suite serially. Maybe it's worth to run tests by default on 2 or 4 workers and run in band e.g. on travis or somewhere?
I wanna see that tests pass without being stupidly slow first. If they do, then we can test by actually spinning up workers 🙂
These have to be fixed first:

haha, it just died 😛 But looking at, and fixing, multiProjectRunner might be what we're missing. If anybody wants to pick it up
Test failures on node 12, that's odd...
whatever that old issue was, it seems to have been fixed 👍

Will need to look into why coverage fails, but this is super promising
Very interesting - tests fail on circus, but passes on GH Actions. The failing test on CI passes on my local machine. Very odd...
for those that want to test this, check this patch-package https://gist.github.com/sibelius/c6ef3f0890814dd4163a9ada0cd739f1
@sibelius very interested in hearing numbers if you play with - does it impact memory/cpu usage?
I've tried to use worker_threads because child process was failing for us, here is the issue https://github.com/facebook/jest/issues/10144
When using worker_threads we got some
CircleCI received exit code 137
137 means Out of Memory.
So worker threads is kind of worse than child process right now for us
mongodb-memory-server was causing OOM for us because it was spinning 1 mongod per test file, we fixed this here https://github.com/shelfio/jest-mongodb/pull/209
but worker_threads still leaking on CircleCI
but it does not leak when running local, --logHeapUsage show always less than 300mb, so not sure if leakage is because of node 12.18.0 or because of docker or circleci specific
we fixed most issues of our tests
and now worker_threads is working fine for us (node 12.18.0)
we didn't notice any improvement in cpu time or memory usage
https://www.npmjs.com/package/piscina just leaving this here as something to maybe explore in the future, who knows, maybe it's faster than jest-workers worker threads farm impl
what is missing here?
how can I enable worker threads on jest config ?
Closing due to inactivity.
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