Fix reading metrics will always get stuck in some cases

[315157973]

Motivation

When javaInstanceRunnable has not been initialized yet, and client calls FunctionsStatsGenerator#generate, the NPE will be triggered.
Since only IOException is caught here, the client's request will be blocked all the time.

The following unit tests are affected and often fail to execute:
org.apache.pulsar.io.PulsarFunctionE2ETest#testReadCompactedSink

Modifications

Catch all exceptions

[eolivelli]

This fix is okay for me

Be can we also fix the NPE ?
do you have a stacktrace ?

if we do not fix the NPE now we will forget about it
a NullPointerException is always a bug and must be fixed.

[315157973]

This fix is okay for me

Be can we also fix the NPE ?
do you have a stacktrace ?

if we do not fix the NPE now we will forget about it
a NullPointerException is always a bug and must be fixed.

This situation will occur when Function startup is not completely finished.But at this time there is a client request.
Even if NPE is not thrown, other exceptions must be thrown.
The status received by the client is all 500, there is no big difference.