max_lock_timeout threshold

gcslock.sh

@@ -26,24 +26,37 @@
 # 	echo "lock acquired"
 # 	unlock mybucket 
 
-# The lock function expects the first (and only) argument to be
-# the name of a bucket writable by the user running this script.
+# The lock function expects the first argument to be the name of
+# a bucket writable by the user running this script.
+# As a second (optional) argument you can pass int value as max
+# lock wait timeout, when total waiting time exceed we will 
+# consider that other running copy of this script died (dead-lock)
+# or could not exited at given time.
 # It creates the lock object in the passed bucket with a special
 # header to obtain mutual exclusion. If the lock object creation
 # fails, it retries indefinitely with expontential backoff.
 
 lock() {
-  if [ "$1" = "" ]
+  bucket="$1"
+  max_lock_timeout="${2:-300}"
+  total_sleep=0
+  if [ "$bucket" = "" ]
   then
     echo "lock: missing bucket argument"
     exit 1
   fi
-  LOCK="gs://$1/lock"
+  LOCK="gs://$bucket/lock"
   sleep_time=1
   while ! echo "lock" | gsutil -q -h "x-goog-if-generation-match:0" cp - $LOCK
   do
     echo "lock: failed to obtain lock, retrying in $sleep_time seconds"
     sleep $sleep_time
+    total_sleep=$((total_sleep+sleep_time))
+    if [ $total_sleep -gt $max_lock_timeout ]
+    then
+      echo "lock: lock timeout ${max_lock_timeout}s exceeded, forcing to get lock"
+      gsutil rm -f $LOCK
+    fi
     sleep_time=$(expr $sleep_time '*' 2)
   done
 }