JDK-8142952 : Unified Logging framework does not allow multiple -Xlog: arguments.
  • Type: Enhancement
  • Component: hotspot
  • Sub-Component: svc
  • Priority: P2
  • Status: Resolved
  • Resolution: Fixed
  • Submitted: 2015-11-13
  • Updated: 2016-02-02
  • Resolved: 2015-11-27
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JDK 9
9 b96Fixed
Related Reports
Duplicate :  
JDK-8143402 - Allow multiple -Xlog arguments to aggregate in unified logging
Description
It seems like Unified Logging outputs must be specified all in a single -Xlog statement.

If you run something like this:  "java -Xlog:thing1 -Xlog:thing2 <program>", you will only get output for thing2! 

The core problem here is that LogConfiguration::parse_log_arguments resets the log configuration each time. As a result, if a second -Xlog option is parsed, parse_log_arguments is called to handle it and deletes the previous configuration.
Comments
Also consider that the test harness may enable one level of logging and a specific test may execute a VM with another level, and combine the test harness VM args. Being able to specify multiple -Xlog options seems pretty fundamental to me, given the potential complexity of a full set of logging options. In fact the JEP specifically allows it for different tags: A new command-line option will be added, to control logging from all components of the JVM. -Xlog Multiple arguments will be applied in the order they appear on command line. Multiple ��-Xlog�� arguments for the same output will override each other in their given order. Last configuration rules. --- If that is not the case then this is a bug not an enhancement.
16-11-2015
Consider the following use case: java -XX:+TraceClassUnloading -Xlog:sometag=level -version TraceClassUnloading is currently being converted to Unified Logging. We want to remove the original logic which sets the TraceClassUnloading flag and use the UL logic instead. To do this, a log configuration must be created when -XX:+TraceClassUnloading is parsed. The problem occurs when "-Xlog:sometag=level" is parsed, the log configuration is reset. So now the question boils down to why the user is still using -XX:+TraceClassUnloading instead of appending the "classunload" tag to their Xlog statement. We wish they wouldn't, but we are continuing to support it as an option. So we need a way to make it play nicely with Unified Logging.
16-11-2015
Any particular reason you want to specify multiple '-Xlog' arguments instead of using complex selectors ( http://openjdk.java.net/jeps/158 )?
16-11-2015