sitescripts: Script to keep services alive

sitescripts/management/bin/start_services.py

+# coding: utf-8
+
+# This file is part of the Adblock Plus web scripts,
+# Copyright (C) 2006-2012 Eyeo GmbH
+#
+# Adblock Plus is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# Adblock Plus is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+
+import os
+from sitescripts.utils import get_config
+
+def _get_services():
+   config = get_config()
+   section_name = "keep_alive_services"
+   section_keys = config.options(section_name)
+   default_keys = config.defaults().keys()
+   keys = set(section_keys) - set(default_keys)
+
+   services = {}
+   for key in keys:
+     services[key] = config.get(section_name, key)
+   return services
+
+def _files_exist(files):
+  for file in files:
+    if not os.path.exists(file):
+      print "'%s' does not exist." % file
+      return False
+  return True
+
+def _process_running(pid):
+  return True

[Wladimir Palant, 2012/11/29 15:01:46]

That still needs to be written, right?

[Felix Dahlke, 2012/11/30 09:49:32]

Um, yes. That's sort of important :) Done.

+
+if __name__ == "__main__":
+  services = _get_services()
+  for service in services.keys():
+    init_file = "/etc/init.d/%s" % service
+    pid_file = "/var/run/%s" % services[service]

[Wladimir Palant, 2012/11/29 15:01:46]

Use os.path.join() here?

[Felix Dahlke, 2012/11/30 09:49:32]

Done.

+
+    if not _files_exist([init_file, pid_file]):

[Wladimir Palant, 2012/11/29 15:01:46]

Actually, if the pid file doesn't exist it means that the service isn't running
- we should start it. And if the init file doesn't exist we should fail -
otherwise we might end up mistakenly relying on this script even though we have
a typo in our configuration.

[Felix Dahlke, 2012/11/30 09:49:32]

Done.

+      continue
+
+    pid_file_content = open(pid_file).read().rstrip()

[Wladimir Palant, 2012/11/29 15:01:46]

I generally prefer to close files explicitly...

[Felix Dahlke, 2012/11/30 09:49:32]

Done.

+    try:
+      pid = int(pid_file_content)
+    except exceptions.ValueError:
+      print "'%s' is not a PID." % pid_file_content
+      continue
+
+    if _process_running(pid):
+      continue
+
+    print "%s is not running, starting ..." % service

[Wladimir Palant, 2012/11/29 15:01:46]

You are aware that any output from a cron job results in a mail to
administrator, right? Then again, maybe that's not a bad thing - if services
need restarting then this justifies a notification.

[Felix Dahlke, 2012/11/30 09:49:32]

Yes, that's what I intended. A crashing service is something we'll want to look
into.

+    subprocess.call([init_file, "start"])