Unexpected error when calling waitForExit

[mihneagiurgea]

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Here's the issue that we're seeing:

ManagedProcess process = builder.build();
process.start();
process.waitForExit(); // Crashes the error below:

waitForExit fails with this:

Caused by: ch.vorburger.exec.ManagedProcessException: Asked to waitFor Program 
[/tmp/75968747865555/MysqlDB4j/base/bin/mysql, -uroot, --socket=/tmp/75968747865555/MysqlDB4j.33803.sock] 
(in working directory /tmp/75968747865555/MysqlDB4j/base), but it was never even start()'ed! |
  |   | at ch.vorburger.exec.ManagedProcess.assertWaitForIsValid(ManagedProcess.java:478)
  |   | at ch.vorburger.exec.ManagedProcess.waitForExitMaxMsWithoutLog(ManagedProcess.java:439) |  
  |   | at ch.vorburger.exec.ManagedProcess.waitForExit(ManagedProcess.java:418) |  
  |   | at com.airbnb.mysql4j.DB.run(DB.java:405) |  
[...]

This is failing randomly, at a rate of say 5%. Succeeds after retries.

Based on the comment from here: https://github.com/vorburger/ch.vorburger.exec/blob/07f251115af56a4f6d38eb46cb2cbd76d10a10ed/src/main/java/ch/vorburger/exec/ManagedProcess.java#L198

... I suspect (without being able to prove this via a test) that what's happening is this, inside startExecute()

1. executor.execute starts execution of something that will fail
2. this.wait(100) returns with no error, but incorrectly fails to detect that the background thread has an error
3. isAlive = watchDog.isWatching() correctly returns False, because the background thread has indeed failed
4. waitForExit will call assertWaitForIsValid(), which throws because isAlive = False (from 3) and hasResult = False (from 2)

[vorburger]

@mihneagiurgea do you want to check if #96 from @cardamon might fix this problem?

[vorburger]

@mihneagiurgea if you are still seeing this with the new 3.1.5 I am about to release, I would welcome a PR to fix!

[vorburger]

@mosesn perhaps you would like to chime in here - do you know if this one can be closed? Still needs a fix?

[mosesn]

I'm still working on the MariaDB4J upgrade–the SLF4J 2.x upgrade is incompatible with some of the versions of the other libraries we use (Spark, Dropwizard, etc) so it has been a bit of a slog. I'm hoping to merge it in soon, and I should be able to give you better feedback once that's done.