KAFKA-3934: Start scripts enable GC by default with no way to disable

…o disable

Author: Grant Henke <granthenke@gmail.com>

Reviewers: Ewen Cheslack-Postava <ewen@confluent.io>

Closes #1631 from granthenke/garbage-flag

bin/kafka-server-start.sh

@@ -5,9 +5,9 @@
 # The ASF licenses this file to You under the Apache License, Version 2.0
 # (the "License"); you may not use this file except in compliance with
 # the License.  You may obtain a copy of the License at
-# 
+#
 #    http://www.apache.org/licenses/LICENSE-2.0
-# 
+#
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -29,7 +29,7 @@ if [ "x$KAFKA_HEAP_OPTS" = "x" ]; then
     export KAFKA_HEAP_OPTS="-Xmx1G -Xms1G"
 fi
 
-EXTRA_ARGS="-name kafkaServer -loggc"
+EXTRA_ARGS=${EXTRA_ARGS-'-name kafkaServer -loggc'}
 
 COMMAND=$1
 case $COMMAND in

bin/zookeeper-server-start.sh

@@ -5,9 +5,9 @@
 # The ASF licenses this file to You under the Apache License, Version 2.0
 # (the "License"); you may not use this file except in compliance with
 # the License.  You may obtain a copy of the License at
-# 
+#
 #    http://www.apache.org/licenses/LICENSE-2.0
-# 
+#
 # Unless required by applicable law or agreed to in writing, software
 # distributed under the License is distributed on an "AS IS" BASIS,
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
@@ -29,7 +29,7 @@ if [ "x$KAFKA_HEAP_OPTS" = "x" ]; then
     export KAFKA_HEAP_OPTS="-Xmx512M -Xms512M"
 fi
 
-EXTRA_ARGS="-name zookeeper -loggc"
+EXTRA_ARGS=${EXTRA_ARGS-'-name zookeeper -loggc'}
 
 COMMAND=$1
 case $COMMAND in