[GitHub] [kafka] C0urante commented on a diff in pull request #12898: optimize: -Dcom.sun.management.jmxremote.rmi.port=$JMX_PORT

[GitBox <gi...@apache.org>]

C0urante commented on code in PR #12898:
URL: https://github.com/apache/kafka/pull/12898#discussion_r1037153804


##########
bin/kafka-run-class.sh:
##########
@@ -212,7 +212,7 @@ fi
 
 # JMX port to use
 if [  $JMX_PORT ]; then
-  KAFKA_JMX_OPTS="$KAFKA_JMX_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT "
+  KAFKA_JMX_OPTS="-Dcom.sun.management.jmxremote.rmi.port=$JMX_PORT $KAFKA_JMX_OPTS -Dcom.sun.management.jmxremote.port=$JMX_PORT "

Review Comment:
   Thanks @reta. To your point--in general, if users want to rely on this undocumented behavior of prioritizing the rightmost value for a system property, they can also use the `$KAFKA_OPTS` variable to declare overrides in case they do not want to alter, e.g., `$KAFKA_JMX_OPTS`.
   
   @a364176773 I understand the desire to simplify implementation, but I'm also trying to satisfy two important principles of bug-squashing:
   1. Limit changes only to the areas that are known to be broken (which in this case, is when the `$JMX_PORT` variable is specified but not the `com.sun.management.jmxremote.rmi.port` system property)
   2. Avoid depending on platform-specific behavior that is not guaranteed by a specification, docs, etc. (which in this case is the prioritization of the rightmost value for a system property on the command line when invoking `java`)
   
   I think the cost of an extra `grep` invocation is a reasonable tradeoff to pay in order to satisfy these tenets, and would like to see that before merging.
   
   Another committer may disagree and feel comfortable merging these changes as-are, but given my limited familiarity with RMI, I'm hesitant to merge this on my own without making absolutely sure that it will have no unintended consequences.



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