[GitHub] [lucene-solr] cpoerschke commented on a change in pull request #2284: SOLR-11233: Add optional JAVA8_GC_LOG_FILE_OPTS for bin/solr.

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

cpoerschke commented on a change in pull request #2284:
URL: https://github.com/apache/lucene-solr/pull/2284#discussion_r568428808



##########
File path: solr/bin/solr
##########
@@ -2026,7 +2026,11 @@ if [ "$GC_LOG_OPTS" != "" ]; then
     if [ "$JAVA_VENDOR" == "IBM J9" ]; then
       gc_log_flag="-Xverbosegclog"
     fi
-    GC_LOG_OPTS+=("$gc_log_flag:$SOLR_LOGS_DIR/solr_gc.log" '-XX:+UseGCLogFileRotation' '-XX:NumberOfGCLogFiles=9' '-XX:GCLogFileSize=20M')
+    if [ -z ${JAVA8_GC_LOG_FILE_OPTS+x} ]; then

Review comment:
       This variant is consistent with the existing variant at line 2010 but yes it confused me too when I first read it, looks there's a subtle difference between "unset" and "set to empty string" behaviour. Illustration:
   
   ```
   $ unset GC_LOG_OPTS
   $ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
   unset
   $ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
   empty
   $ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
   empty
   $ 
   $ GC_LOG_OPTS=
   $ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
   not unset
   $ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
   empty
   $ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
   empty
   $
   $ GC_LOG_OPTS=foobar
   $ if [ -z ${GC_LOG_OPTS+x} ]; then echo unset; else echo not unset; fi
   not unset
   $ if [ -z ${GC_LOG_OPTS:+x} ]; then echo empty; else echo not empty; fi
   not empty
   $ if [ -z ${GC_LOG_OPTS} ]; then echo empty; else echo not empty; fi
   not empty
   ```




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