[BUG] Invalid JMX options causes silent exit

[XA21X]

Describe the bug
Invalid --jmx- prefixed options causes the program to exit with no error message.

To Reproduce
java -jar minotaur.jar -s some-dc --jmx-bad

Expected behavior
Like non-JMX options, it should print the error Unknown option: '--jmx-bad' followed by usage instructions.

System and versions:

• macOS Monterey 12.1 on M1 Pro (arm64)
• OpenJDK 64-Bit Server VM Zulu11.52+13-CA (build 11.0.13+8-LTS, mixed mode)
• Minotaur 1.0.2-SNAPSHOT (current master)

[XA21X]

Initial investigation

The picocli.CommandLine.DefaultExceptionHandler#internalHandleParseException looked like it should be sufficient for printing a suitable error message, but why isn't it working? I double checked it's writing to the PrintWriter that's backed by the correct System.err object. It turns out the internal handler writes without flushing, and the PrintWriter we provide from com.instaclustr.picocli.CLIApplication#execute(picocli.CommandLine, java.lang.String...) does not have auto-flush turned on, so the error output gets lost.

While debugging, I could manually flush the writers to obtain the output:

Unknown option: '--jmx-bad'
Possible solutions: --jmx-service, --jmx-user, --jmx-password, --jmx-credentials, --jmx-truststore, --jmx-truststore-password, --jmx-keystore, --jmx-keystore-password, --jmx-client-auth

Proposed Solution

Enable auto-flushing for both PrintWriters at https://github.com/instaclustr/instaclustr-commons/blob/94294f6dea4c62cbfcae34de4ea41051aa02356e/src/main/java/com/instaclustr/picocli/CLIApplication.java#L21

[smiklosovic]

thanks @XA21X , I ll merge it soon.

[smiklosovic]

fixed here, (not released yet) instaclustr/instaclustr-commons#7