Use "info" as the default root logger level

[merlimat]

Motivation

In #3661 the root logger level was made configurable and the level was changed from info to debug.

That change had the side effect that the control:

if (log.isDebugEnabled()) {
  log.debug("{}", computeExpensiveString());
}

is now passing the if condition and it's triggering the call to computeExpensiveString() whose value is then never printed. This happens for all non pulsar logger (eg. org.apache.zookeeper.. client logs), with the result of lot of garbage getting created.

Changing back the default value to info.

[massakam]

rerun java8 tests

[cdbartholomew]

I believe that this new default was also triggering a bug 3113 in jetty: "Logging of key.readyOps() can throw unchecked CancelledKeyException"

This bug is only exposed if debug logging is enabled:

if (LOG.isDebugEnabled()) LOG.debug("selected {} {} {} ",key.readyOps(),key,attachment);

I was seeing this in the broker after sending lots of REST requests. After hitting this bug, the broker no longer responds to REST requests, so it's pretty ugly.

Once I changed root level logging to info, I no longer see the jetty bug.

I think this is an important change to get in the next milestone so people don't trip over this. It's also something to note can happen with debug logging enabled the broker even when this default is changed, so it might be worth considering upgrading the jetty version. The jetty bug is fixed in 9.4.15 (current Pulsar version is 9.4.12).