Hi Ceki, We have observed a strange behavior of the logger slf4j-simple when two or more parallel Maven modules log the exceptions and the messages.
It produces corrupted lines in the log and they are partially mixed with other lines. The lines look like this and they are obviously not expected in the log. [ERROR] R] *********.util.json.formatter.JsonFormatterTest [ERROR] Process Exit Code: 0 [ERROR] *********.util.json.formatter.JsonFormatterTest After our analysis we found the place in SLF4J code which seems to be the root cause. The method [1] is a critical section and must be synchronized with a singleton lock which avoids reordering of the nested method calls across multiple Threads. Without it, the normal messages and stack trace may mix especially if two parallel Maven modules print the stacktrace. [1]: https://github.com/qos-ch/slf4j/blob/39e3b81e5ea69c6610c8d5fd57fd974e090d9fc1/slf4j-simple/src/main/java/org/slf4j/simple/SimpleLogger.java#L243 Pls analyse the class SimpleLogger.java and answer with your opinion about this issue and a proposal with the fix. If there are more other critical sections which need to have some concurrency treatments, we can talk about it in this mailing list. -- Cheers Tibor
