LOG4J2-3060 Fix integer overflow in DefaultErrorHandler

[Noobgam]

When configured incorrectly, the ErrorHandler::error method will be called very often. As an example of such behavior, you can try stopping the appender manually.

This will result in ErrorHandler::error("Attempted to append to non-started appender {...}") which may or may not be called often. In our scenario, this happened ~4k-20k times per second. Although everything seems normal at first, exceptionCount keeps getting incremented until it overflows after 2^31 increments.

When it overflows, every such method call will enter the branch leading to very high CPU consumption in useless code and a significant spike in System.out throughput

[carterkozak]

Thank you for reporting, great find! Would you mind filing jira issue for tracking here?

[Noobgam]

Sure https://issues.apache.org/jira/browse/LOG4J2-3060

[rgoers]

This looks good to me. It needs to be back-ported to releaes-2.x. I believe we should be able to cherry pick the commit.

[zhurs]

@rgoers
I met this problem in my production.
What can we do to merge this fix?

[vy]

Superseded by #597.