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Backwards Compatibility:
Fully Compatible
Operating System:
ALL
Backport Requested:

v4.4
Steps To Reproduce:
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The sleep(5000) is to ensure the parallel shell has already exited by the time MongoRunner.runningChildPids() is called.

./mongo --nodb --eval 'var cleanup = startParallelShell("1", undefined, true); sleep(5000); try { MongoRunner.runningChildPids(); throw new Error('Simulating assert.soon() failure'); } finally { cleanup() }'
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The sleep(5000) is to ensure the parallel shell has already exited by the time MongoRunner.runningChildPids() is called. ./mongo --nodb --eval 'var cleanup = startParallelShell("1", undefined, true); sleep(5000); try { MongoRunner.runningChildPids(); throw new Error('Simulating assert.soon() failure'); } finally { cleanup() }'
Sprint:
STM 2020-06-29, STM 2020-07-13
Linked BF Score:
50

The MongoRunner.runningChildPids() function calls through to getRunningMongoChildProcessIds() in shell_utils_launcher.cpp, which in turn calls wait_for_pid() on all processes in ProgramRegistry::_registeredPids. A JavaScript test of the form

let cleanup;
try {
    cleanup = startParallelShell(...);
    assert.soon(...);
    ...
} finally {
    cleanup();
}

(for example) would end up calling wait_for_pid() multiple times. The first call to wait_for_pid() via getRunningMongoChildProcessIds() would unregister the pid from ProgramRegistry::_registeredPids and the second call would trigger this invariant.

is caused by

SERVER-43153 Expose pids of spawned processes in the shell

related to

SERVER-49347 Fix locking in shell's ProgramRegistry