set flags in JAVA_OPTS to speed up java connector startup latency in tests

[postamar]

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Relevant information

The performance investigation of the tests in source-postgres revealed that java connector containers could require the better part of a second to do something as basic as respond to a spec API call. See #31298 (comment)

Part of what causes the latency to be high is that the JVM default settings are tuned for long-running operation. This is fine for us in a production setting but in tests these JVMs are typically short-lived. I've found that making the JIT less aggressive with -XX:TieredStopAtLevel=1 would speed things up noticeably. Perhaps there's other flags and settings worth using, I don't know yet.

Furthermore another cause of startup latency involves the logger. I don't think tests care much about the logs and overriding the log4j configuration with something like -Dlog4j.configurationFile=<some nonexistent path> would speed things up as well. Alternatively, we can add a very simple but valid log4j-for-integration-testing.propertiesresource file in the CDK somewhere and refer to it with-Dlog4j.configuration=`.

[postamar]

I'm wrong about the tests not caring about the connector logs. I found them to be quite useful the other day!