lhotari opened a new pull request, #15670:
URL: https://github.com/apache/pulsar/pull/15670
### Motivation
- The GC logs don't currently include the safepoint time
- This is necessary for investigating long GC pauses
- Writing GC logs impacts the total duration of a "stop the world" pause.
Add ways to address this problem.
- For <Java 17, it is necessary to be able to write GC logs to a tmpfs or
a fast disk that isn't saturated. See ["Eliminating Large JVM GC Pauses Caused
by Background IO
Traffic"](https://engineering.linkedin.com/blog/2016/02/eliminating-large-jvm-gc-pauses-caused-by-background-io-traffic)
for more details.
- On Java 17+, there's an option `-Xlog:async`, explained in
https://bugs.openjdk.java.net/browse/JDK-8264323 . This addresses the problem
explained in the [blog
post](https://engineering.linkedin.com/blog/2016/02/eliminating-large-jvm-gc-pauses-caused-by-background-io-traffic)
referenced above.
- The GC log is currently always placed in `logs` directory.
`PULSAR_LOG_DIR`/`BOOKIE_LOG_DIR` option is ignored. The GC log should go to
the correct directory.
### Modifications
- include the safepoint time in GC logs
- Add "safepoint" to logged "tags" for Java 9+ and
-XX:+PrintGCApplicationStoppedTime for Java 8
- make it possible to specify the GC logs directory with `PULSAR_GC_LOG_DIR
/`BOOKIE_GC_LOG_DIR` , default to `PULSAR_LOG_DIR`/`BOOKIE_LOG_DIR`.
- the logging layout is now common for both Pulsar and BK GC logs
using "time,uptime,tags".
- Add `-Xlog:async` to GC logging options on Java 17+
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