Background Threads as Daemon?

[thgau]

The two threads (tjahzi-worker and ReadingLogBufferAndSendingHttp) are not marked as DaemonThreads. Is there a reason for this?

[tkowalcz]

Default thread factory from Netty does not use daemon threads, but looks like Netty 5.0 does.

ReadingLogBufferAndSendingHttp thread is part of Agrona agent "framework" that also does not set threads to daemon by default. If Tjahzi is shut down correctly it should also close all its threads cleanly. Did you see any problems with that?

That being said I'm ok with changing those threads to be daemons.

[thgau]

No need to hurry. As I said: it usually works...

[tkowalcz]

Hi. I investigated more deeply how Log4j2 does the shutdown and here are my findings. See also this (a little old) discussion.

In a "normal" application with public static void main(String[] args) I need to call LogManager.shutdown() to init a proper shutdown sequence. Then application exits cleanly.
When I change Tjahzi threads to be daemon threads then after main exits the shutdown hook registered by Log4j2 is executed and whole application exits cleanly. So this is definitely the way to go.

[tkowalcz]

As for your experiment. After log4j2 shutdown LokiAppender::stop method is called and Tjahzi attempts to shut down its threads. There is a shutdownTimeoutSeconds configuration value that controls how long it waits for log shipper thread to end. After that timeout the shutdown sequence continues. If you extend value of shutdownTimeoutSeconds to very large number will the message consistently appear in Loki?

[thgau]

Actually I can no more reproduce the problem. I do not know what was different a week ago. In the meantime I switched between the nodep and the plain version and from 0.9.17 to 0.9.18 but in none of these versions I get the problem any more. Currently it works fine, the last log message arrives and then the tjahzi-worker exits. I am sorry that you spent time in this problem.

[tkowalcz]

No problem. I learned few more things about log4j, it's all for the better.