Dremio version 25 and later no longer support Java 8. Java 11 is required.

To troubleshoot garbage collection and heap issues, customers have previously been asked to set a number of JVM switches to capture extra logging, for example:

 -Xloggc:/opt/dremio/data/log/gc.log
  -XX:+UseGCLogFileRotation
  -XX:NumberOfGCLogFiles=1
  -XX:GCLogFileSize=4000k
  -XX:+PrintGCDetails
  -XX:+PrintGCTimeStamps
  -XX:+PrintGCDateStamps
  -XX:+PrintClassHistogramBeforeFullGC
  -XX:+PrintClassHistogramAfterFullGC

These options are no longer allowed in Java 11 and will cause Dremio to fail to start up, with an error similar to :

Unrecognized VM option 'UseGCLogFileRotation'

New options for Java 11

Java 11 uses "JVM unified logging" with a new set of parameters.

The equivalent JVM switches for the above gc log settings would be :

-Xlog:gc*,classhisto*=trace:file=/opt/dremio/data/log/gc.log:uptime,time,tags,level:filecount=1,filesize=4M

Breaking that down:

New parameter	Old equivalent	Description
-Xlog:		Use the Xlog framework
gc*	-Xloggc:	Log messages tagged with at least 'gc' up to 'info' level
classhisto*=trace	-XX:+PrintClassHistogramBeforeFullGC -XX:+PrintClassHistogramAfterFullGC	Print a class histogram before and after any major stop-world GC
file=<filename>	-Xloggc:<filename>	Filename to use as the gc log file.
uptime		Include the time since the JVM started in all log messages
time	-XX:+PrintGCTimeStamps -XX:+PrintGCDateStamps	Include the time in all log messages
tags		Include all tags relevant to each message - e.g. [gc,cpu ]
level		Include the logging level of each message
filecount=1	-XX:NumberOfGCLogFiles=1	Number of files to keep in rotation (not counting the active file)
filesize=4M	-XX:GCLogFileSize=4000k	Max size of each log file

Adding timestamp to the file name

One can add %t to the file parameter which uses the JVM startup date and time in the filename, this can be desirable but, this will change the meaning of filecount so that

-Xlog:gc*,classhisto*=trace:file=gc-%t.log

will result in files with the following names assuming filecount=1 as you will note this means the limit of 1 is not achieved for all files

gc-2024-06-14_16-50-07.log

gc-2024-06-14_16-50-07.log.0

gc-2024-06-13_12-40-07.log

gc-2024-06-13_12-4--00.log.0

New options for Java 11

Adding timestamp to the file name

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