log4j2-appender producer name should be configurable

[tkram01]

When using the log4j2-appender it always gives a producer name of "pulsar-log4j2-appender-" + topic which means you can only send logs from one process to that topic at a time. When there are multiple instances of an application I think it makes sense to be able to consolidate them into a single topic.

[jiazhai]

Thanks @tkram01 for report this requirements.

I think it makes sense to be able to consolidate them into a single topic

The 'topic' in log4j2 appender is configurable,
If user want to append all logs into a single topic, only need to set the same topic name.
If want to append to different topic, user also could set the different topic name.
I may not understand it well, Would you please provide an example for the requirement?

[sijie]

@jiazhai we might consider adding documentation for this.

[Jennifer88huang-zz]

I add the following note in "reference-configure/log4j". If we need more info, please provide, and I'll improve it further in PR-7297

'topic' in log4j2.appender is configurable.

• If you want to append all logs to a single topic, set the same topic name.
• If you want to append logs to different topics, you can set different topic names.