Add "threads" command to the gerrit.sh script

Make it easier to create Gerrit server thread dumps by providing a
command for that in the gerrit.sh. This also makes it easier to explain
people in the Gerrit discussion group how to provide a thread dump.

Change-Id: I92b75d1ed4c19feba715c83857e94fde79e45c16

gerrit-pgm/src/main/resources/com/google/gerrit/pgm/init/gerrit.sh

@@ -47,7 +47,7 @@
 
 usage() {
     me=`basename "$0"`
-    echo >&2 "Usage: $me {start|stop|restart|check|status|run|supervise} [-d site]"
+    echo >&2 "Usage: $me {start|stop|restart|check|status|run|supervise|threads} [-d site]"
     exit 1
 }
 
@@ -63,6 +63,13 @@ running() {
   return 0
 }
 
+thread_dump() {
+  test -f $1 || return 1
+  PID=`cat $1`
+  $JSTACK $PID || return 1
+  return 0;
+}
+
 get_config() {
   if test -f "$GERRIT_CONFIG" ; then
     if test "x$1" = x--int ; then
@@ -258,6 +265,8 @@ if test -z "$JAVA" ; then
   exit 1
 fi
 
+JSTACK=${JAVA:0:${#JAVA}-5}/jstack
+
 #####################################################
 # Add Gerrit properties to Java VM options.
 #####################################################
@@ -536,6 +545,16 @@ case "$ACTION" in
     exit 3
   ;;
 
+  threads)
+    if running "$GERRIT_PID" ; then
+      thread_dump "$GERRIT_PID"
+      exit 0
+    else
+      echo "Gerrit not running?"
+    fi
+    exit 3
+  ;;
+
   *)
     usage
   ;;