Tuesday, January 27, 2015

Why am I getting "WARNING arguments left: 1"

If you are new to Akka Logging and are used to using Log4j, there is a good chance you will get the error "WARNING arguments left: 1", and not know where its coming from.

So, here it is:
In log4j, you maybe used to writing:
logger.warn("Exception caught: ", e);

This is perfectly valid and works fine. If you use this line in akka logging, you will get the error "WARNING arguments left: 1" because in the case of logback, the syntax assumes it is filling in params from the string, so it expects this:
logger.warning("Exception caught: {}", e);
Hope this will help all of us (including me) not to get caught by this again....


  1. logger.error(e,"Exception caught");

  2. Thank you, it is quite helpful

  3. Agree with Unknown above, in most cases I think logger.error(e, "Problem doing X") is a better approach because your logging system can deal with the Exception directly, instead of just getting a toString version of the Exception (usually the message field). With an out of the box configuration this means you'll actually get the stack trace in the logs.