Merge "Create systemwide lock for glean"

glean/cmd.py

@@ -23,6 +23,8 @@ import subprocess
 import sys
 import time
 
+from glean import systemlock
+
 post_up = "    post-up route add -net {net} netmask {mask} gw {gw} || true\n"
 pre_down = "    pre-down route del -net {net} netmask {mask} gw {gw} || true\n"
 
@@ -412,12 +414,13 @@ def main():
         '--skip-network', dest='skip', action='store_true',
         help="Do not write network info")
     args = parser.parse_args()
-    if args.ssh:
-        write_ssh_keys(args)
-    if args.hostname:
-        set_hostname_from_config_drive(args)
-    if args.interface != 'lo' and not args.skip:
-        write_network_info_from_config_drive(args)
+    with systemlock.Lock(os.path.join(args.root, 'tmp/glean.lock')):
+        if args.ssh:
+            write_ssh_keys(args)
+        if args.hostname:
+            set_hostname_from_config_drive(args)
+        if args.interface != 'lo' and not args.skip:
+            write_network_info_from_config_drive(args)
     return 0
 
 

glean/systemlock.py

@@ -0,0 +1,30 @@
+#!/usr/bin/python
+# Copyright (c) 2015 Hewlett-Packard Development Company, L.P.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+# implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import fcntl
+
+
+class Lock(object):
+    def __init__(self, filename):
+        self.filename = filename
+
+    def __enter__(self):
+        fh = open(self.filename, 'w')
+        fcntl.flock(fh, fcntl.LOCK_EX)
+
+    def __exit__(self, exc_type, exc_value, traceback):
+        fh = open(self.filename, 'w')
+        fcntl.flock(fh, fcntl.LOCK_UN)