Lock

rsync/runsync.sh

 #!/bin/bash
 
 OUTPUT='/alloc/output.json'
+LOCKFILE='/repo/.rsynclock'
 
 log () {
   mapfile IN
@@ -19,6 +20,24 @@ error () {
 EOF
 }
 
+# Let's make absolutely sure there's only one copy of the job running
+if [[ -f "$LOCKFILE" ]]; then
+  # The lockfile exists, let's check if it's fresh
+  AGE=$((`date +%s` - `stat -c '%Y' $LOCKFILE`))
+  if [[ $AGE -gt 86400 ]]; then
+    echo "$LOCKFILE is over 24 hours old. It's probably stale, so get rid of it."
+    rm -f "$LOCKFILE"
+  fi
+fi
+
+# Grab the lock, exit if you fail
+if !(set -o noclobber; echo "`hostname` ($$)" > "$LOCKFILE") 2> /dev/null; then
+  echo "Lock exists: $LOCKFILE owned by $(cat $LOCKFILE)"
+  exit
+fi
+
+# Delete the lock if we die
+trap 'rm -f "$LOCKFILE"; exit $?' INT TERM EXIT
 
 # Read the job parameters
 if [[ "${TOOL}" == "rsync" ]]; then
@@ -58,3 +77,7 @@ cat << EOF | log > $OUTPUT
   "message_type": "result",
   "exit_code": ${RET}
 EOF
+
+# Clean up after yourself, and release your trap
+rm -f "$LOCKFILE"
+trap - INT TERM EXIT