Fix log rotation in daemon mode

When daemon mode is started as root and the user is changed to a lower
privilege user the log rotation breaks.  This is because the log file is still
owned by root.

Now just before we switch user the log file user is changed to the new user.

Fixes bug# 1079743

Change-Id: Ia35e44bf9c891ce85a66e64989f97d3195520891

README

@@ -72,7 +72,8 @@ Basic commands:
     $ libra_worker --debug --nodaemon
 
 NOTE: When running the worker in daemon mode, you must make sure that the
-directory where the PID file will be (-p/--pid option) exists and is writable
+directory where the PID file will be (-p/--pid option) and the directory where
+the log files will be written (-l/--logfile option) exists and is writable
 by the user/group specified with the --user and --group options. Also, the
 Python module used to start the daemon process does not like it when the PID
 file already exists at startup.

libra/mgm/mgm.py

@@ -265,6 +265,9 @@ def main():
             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

libra/worker/main.py

@@ -16,6 +16,7 @@ import eventlet
 eventlet.monkey_patch()
 
 import daemon
+import os
 import daemon.pidfile
 import grp
 import pwd
@@ -137,6 +138,9 @@ def main():
             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