We probably need to add a small amount of logging in the new producer and (soon) consumer clients. I wanted to have a quick discussion on logging libraries before I start adding this in the producer.
Previously we have been pretty verbose loggers and I think we should stop that. For clients you mostly don't need to log: if there is an error you should throw it back not log it, so you don't need ERROR logging. Likewise I think it is rude to pollute peoples logs with the details of client initialization (establishing connections, etc), so you don't need INFO logging. However perhaps there is an argument to be made for WARN and DEBUG. I think it is perhaps useful to log a WARN when a server breaks a connection or metadata initialization fails. It can sometimes also be useful to be able to enable debug logging to see step by step processing in the client, which is the case for DEBUG logging. Here is my knowledge about the state of Java logging: 1. Most people still use log4j. The server is using log4j. 2. Second runner-up in slf4j. I personally consider slf4j pretty silly but this is perhaps the more flexible choice since people can plug in different stuff. 3. java.util.logging ships with the jdk, but for some reason no one uses it. 4. There is no critical mass around any other logging library. The context for how to think about this is the following. We are not trying to pick the "best" logging library. Fundamentally logging is pretty straight-forward and for our simple use case it is inconceivable that any particular library could be much better than any other in terms of feature set. We want the most standard library. My goal is to minimize the dependencies of the client and make our basic logging cases work for most cases. Is there a reason not to just the java.util.logging? It comes with the jdk and supports pluggable appenders so people who have some other library can plug that in right? Basically my preference would be java.util.logging unless there is some known problem with it, otherwise I guess slf4j, and if not that then log4j. Thougts? -Jay
