instruct java to store heap dumps in case of OOM

hosts/jenkins/etc/default/jenkins

@@ -10,7 +10,7 @@ JAVA=/usr/bin/java
 #JAVA_ARGS="-Djava.awt.headless=true"  # Allow graphs etc. to work even when an X server is present
 #JAVA_ARGS="-Xmx256m"
 #JAVA_ARGS="-Djava.net.preferIPv4Stack=true" # make jenkins listen on IPv4 address
-JAVA_ARGS="-Djava.awt.headless=true -Xmx3072m -XX:MaxPermSize=384m"
+JAVA_ARGS="-Djava.awt.headless=true -Xmx3072m -XX:MaxPermSize=384m -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/var/lib/jenkins/heapDumps/"
 
 PIDFILE=/var/run/$NAME/$NAME.pid
 

hosts/jenkins/etc/init.d/jenkins

@@ -92,6 +92,11 @@ check_tcp_port() {
 #
 do_start()
 {
+    # java will store heap dumps here in case of OutOfMemoryError.
+    # delete old heap dumps when starting
+    rm -r "$JENKINS_HOME/heapDumps/" > /dev/null 2>&1 || true
+    mkdir -p "$JENKINS_HOME/heapDumps/"
+    chown ${JENKINS_USER}.${JENKINS_GROUP} "$JENKINS_HOME/heapDumps"
     # the default location is /var/run/jenkins/jenkins.pid but the parent directory needs to be created
     mkdir `dirname $PIDFILE` > /dev/null 2>&1 || true
     chown $JENKINS_USER `dirname $PIDFILE`