Docker for Mac 2.0.0.2: empty logs for short-lived containers

[rnorth]

I've noticed an issue that I can reliably reproduce on Docker for Mac 2.0.0.2, but which does not appear on CI.

org.testcontainers.utility.DirectoryTarResourceTest#simpleRecursiveFileTest will fail ~80% of the time for me. This particular test uses a short-lived container comprising a cat CMD and with OneShotStartupCheckStrategy. The test attaches a ToStringConsumer to logs and waits for the end of stdout logs to be reached.

Some of the time, when the test passes, the log stream callback events are onStart, onNext (containing the desired stdout line) and onComplete.

After adding a little extra instrumentation, it appears that most of the time the log stream callback events are onStart, onComplete. onNext is never fired.

In this situation the test fails. However, when attempting to read the logs later, the correct log message is found.

My hypothesis is that this version of Docker automatically triggers the onComplete event at container exit even if there are unflushed stdout/stderr frames.

[rnorth]

Bizarrely I don't get this issue on all of my Macs...