Add daemon framework for an API server (copied from other parts of Libra)

Change-Id: I7a94a3e2938734ec1594ba33f950aaea14b65980

libra/api/__init__.py

@@ -0,0 +1,13 @@
+# Copyright 2013 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.

libra/api/main.py

@@ -0,0 +1,76 @@
+# Copyright 2013 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 daemon
+import daemon.pidfile
+import daemon.runner
+import grp
+import pwd
+
+from libra.common.options import Options, setup_logging
+
+
+class APIServer(object):
+    def __init__(self, logger, args):
+        self.logger = logger
+        self.args = args
+
+
+def main():
+    options = Options('api', 'API Daemon')
+    args = options.run()
+
+    logger = setup_logging('api_server', args)
+    server = APIServer(logger, args)
+
+    if args.nodaemon:
+        server.main(task_list)
+    else:
+        pidfile = daemon.pidfile.TimeoutPIDLockFile(args.pid, 10)
+        if daemon.runner.is_pidfile_stale(pidfile):
+            logger.warning("Cleaning up stale PID file")
+            pidfile.break_lock()
+        context = daemon.DaemonContext(
+            working_directory='/etc/libra',
+            umask=0o022,
+            pidfile=pidfile,
+            files_preserve=[logger.handlers[0].stream]
+        )
+        if args.user:
+            try:
+                context.uid = pwd.getpwnam(args.user).pw_uid
+            except KeyError:
+                logger.critical("Invalid user: %s" % args.user)
+                return 1
+            # NOTE(LinuxJedi): we are switching user so need to switch
+            # the ownership of the log file for rotation
+            os.chown(logger.handlers[0].baseFilename, context.uid, -1)
+        if args.group:
+            try:
+                context.gid = grp.getgrnam(args.group).gr_gid
+            except KeyError:
+                logger.critical("Invalid group: %s" % args.group)
+                return 1
+
+        try:
+            context.open()
+        except lockfile.LockTimeout:
+            logger.critical(
+                "Failed to lock pidfile %s, another instance running?",
+                args.pid
+            )
+            return 1
+
+        server.main()
+    return 0