[minor] add locking to scheduler

webnotes/utils/file_lock.py

@@ -0,0 +1,39 @@
+import os
+from time import time
+from webnotes.utils import get_site_path
+
+class LockTimeoutError(Exception):
+    pass
+
+def create_lock(name):
+	pre
+	lock_path = get_lock_path(name)
+	if not check_lock(lock_path):
+		return touch_file(lock_path)
+	else:
+		return False
+
+def touch_file(path):
+	with open(path, 'a'):
+		os.utime(path, None)
+	return True
+
+def check_lock(path):
+	if not os.path.exists(path):
+		return False
+	if time() - os.path.mtime(path) > 600:
+		raise LockTimeoutError(path)
+	return True
+
+def delete_lock(name):
+	lock_path = get_lock_path(name)
+	try:
+		os.remove(path)
+	except OSError:
+		pass
+	return True
+
+def get_lock_path(name):
+	name = name.lower()
+	lock_path = get_site_path(name + '.lock')
+	return lock_path

wnf.py

@@ -454,9 +454,13 @@ def reset_perms(site=None):
 # scheduler
 @cmd
 def run_scheduler(site=None):
+	from webnotes.utils.file_lock import create_lock, delete_lock
 	import webnotes.utils.scheduler
-	webnotes.connect(site=site)
-	print webnotes.utils.scheduler.execute()
+	webnotes.init(site=site)
+	if create_lock('scheduler'):
+		webnotes.connect(site=site)
+		print webnotes.utils.scheduler.execute()
+		delete_lock('scheduler')
 	webnotes.destroy()
 
 @cmd