GC Logs changes for migrating from JDK 8 to JDK 11.

Problem :

Moving from JDK 8 to JDK 11 is quiet subtle. One issue which many people have faced is regarding is GC Logs.

Solution :

JDK 11 uses generic logging mechanism. So flags like PrintGCDetails, PrintGCDateStamps don’t work anymore. The new format is easy to use once you understand it.

Format is :

[tag selection][:[output][:[decorators][:output-options]]]

There are 4 sections to it :

1. What operation do you want to log and what level you want to log.
2. Where do you want to log.
3. What parameter’s you want to log.
4. Any additional options.

For e.g.

-Xlog:gc:file=/var/logs/gc.log:utctime,pid,level,tags:filecount=3,filesize=100M

In the above case, we wanted to see gc logs at specified log file showing mentioned variable with max of 3 back up files to be rolled when main file reached 100 MB.

More information is available at : https://docs.oracle.com/javase/9/tools/java.htm#JSWOR-GUID-BE93ABDC-999C-4CB5-A88B-1994AAAC74D5