Ensure only one instance of update_commited_patches runs at a time

I saw a problem where the script hung, then other copies came along and
things just cascaded. This is a simple hack to exit with an error if the
script is already running.

Change-Id: I7eeb5e072f69c93e5e1d6b4ef6e0c6126ca4cb0c

1 files changed, 9 insertions, 0 deletions

diff --git a/update_commited_patches.py b/update_commited_patches.py
index d930fef..633eccf 100755
--- a/update_commited_patches.py
+++ b/update_commited_patches.py
@@ -1,8 +1,10 @@
 #!/usr/bin/python
 
+import fcntl
 import logging
 import os
 import operator
+import sys
 
 from bin import django_setup, add_logging_arguments
 django_setup()  # must be called to get sys.path and django settings in place
@@ -76,6 +78,13 @@ if __name__ == '__main__':
 
     _assert_repo_dir(settings.REPO_DIR)
 
+    # Ensure no other copy of this script is running
+    f = open(os.path.join(settings.REPO_DIR, '.lock'), 'w+')
+    try:
+        fcntl.flock(f, fcntl.LOCK_EX | fcntl.LOCK_NB)
+    except IOError:
+        sys.exit('Script is already running')
+
     if args.project:
         projects = [Project.objects.get(linkname=args.project)]
     else: