"mbemon" ("Myth Backend Monitor") is a script that will monitor your Myth backend process for certain error conditions and automatically restart the backend process if any of the following conditions are detected:

1. Growth of the backend log file to more than 1MB.
2. "waiting for a thread" messages in the backend log file.
3. Backend process does not exist.
4. Failure of backend to respond to status queries on port 6544.

If any of these conditions are detected mbemon automatically:

1. Captures diagnostic information that can be used to determine the root-cause of the problem.
2. Restarts the Myth back-end process.
3. Restarts gdm and the myth front-end process.

I implemented this script because I found that the backend would occasionally exit and recordings would not occur until I noticed the problem and restarted the backend. Now, no more lost recordings. mbemon is packaged with the Knoppmyth R5D1 release. I am currently using it with R5A30.2. A copy of the script can be found in the knoppmyth forums in the second post of the following thread: http://mysettopbox.tv/phpBB2/viewtopic.php?t=10998&postdays=0&postorder=asc&start=0

Starting mbemon

To start mbemon automatically at boot time add the following line to the end of the file /etc/init.d/bootmisc.sh:

You can manually start mbemon at anytime as root by entering the command "/etc/init.d/mbemon start" and you can halt it by entering the command "/etc/init.d/mbemon stop". If is important that you halt mbemon before you run mythbackup or any other process that needs the myth backend stopped. If you don't do this, mbemon will detect that missing mythbackend process and automatically restart it, even though you deliberately halted mythbackend.

Diagnostic information

mbemon maintains the following files in the directory /var/log/mythtv/mbemon

1. mbemon.log: When mbemon is started this file is initialized with a single line that indicates the date and time mbemon was started. After that, each time mbemon detects the need to restart the backend, information is added to the end of this log file that indicates the time the restart happened and the reason that mbemon felt that a restart was necessary.
2. history.log: A single line is added to this file everytime that mbemon does a status check on the backend. The file is limited in size to 15 lines.
3. status.txt: The output from the last status query sent to the Myth backend.
4. mythbackend.log: When mbemon detects the need to restart the backend, it automatically moves /var/log/mythtv/mythbackend.log to location. This is helpful for diagnosing the root-cause of the backend problem. mbemon maintains a history of the last 4 backend log files in case multiple restarts happen. In chronological order from more recent to oldest they are named "mythbackend.log", "mythbackend.log-1", "mythbackend.log-2" and "mythbackend.log-3".

Finally, as a safety precaution mbemon will terminate itself if the backend process has required a restart on 4 of the last 15 checks, as this likely indicates that existence of a persistent error that must be addressed to achieve stability.