Logging
MythTV (starting with version 0.25) supports logging to various loggers. Logging to them is enabled with command-line arguments. Additional information about application command-line arguments is available using the --help
argument, for example:
mythbackend --help
or
mythfrontend --help
Detailed help information is available for each argument by including the argument name after --help
, for example:
mythbackend --help setloglevel mythbackend --help logpath
Contents
General
All logging (regardless of specified logger) is affected by the arguments:
--setloglevel Change logging level of the existing master backend. --verbose OR -v Specify log filtering. Use '-v help' for level info.
Typically, the default value for --setloglevel
and --verbose
are appropriate for normal application execution. However, you may be asked to provide logs at a specific log level when helping debug issues.
Loggers
Console Logging
If running a MythTV application in a non-daemon mode, console logging will be enabled. Console logging is output to stdout
.
Console logging is automatically disabled with the argument:
--daemon OR -d Fork application into background after startup.
(for MythTV daemon applications).
The console logging output contains a shortened format which better fits a standard terminal. Therefore, please provide full file logging output when attaching log files to bug tickets.
File Logging
The primary logger for MythTV applications is the file logger. File logging outputs detailed "debug" logging information about process execution, which can be very useful in debugging issues with MythTV. All log files uploaded to bug tickets should be those created from the file logger.
File logging is disabled by default and may be enabled with the argument:
--logfile OR --logpath OR -l Writes logging messages to a file at logpath. If a directory is given, a logfile will be created in that directory with a filename of applicationName.date.pid.log. If a full filename is given, that file will be used. This is typically used in combination with --daemon, and if used in combination with --pidfile, this can be used with log rotators, using the HUP call to inform MythTV to reload the file (currently disabled).
When specifying a file path, file logging is only enabled for the application you are starting. All logging will be disabled for child processes started by that application (for example, preview generation, commercial detection, transcoding, and other jobs started by mythbackend). Therefore, you should always specify a directory as the argument for --logpath
or -l
.
File logging output may be challenging to read in a terminal due to the amount of information included. You may simplify the log file output with a log processor. For example, the command:
perl -pwe 's#^(\d{4}(?:-\d{2}){2} \d{2}(?:\:\d{2}){2}\.\d{6} \w) \[\d+/\d+\] \S+ \S+ \(\S+\) - (.*$)#$1 $2#' /path/to/logfile
will scan the log file at /path/to/logfile
and output (to stdout
) a simplified log format equivalent to that used by console logging. Change the /path/to/logfile
, as appropriate for your system.
Note: Currently, mythfilldatabase
has separate logging for the command itself and for the wget
command it calls.
The following sample changes are made using mythtv-setup
; select General, Program Schedule Download Options:
Guide data arguments: --logpath /var/log/mythtv (added to existing arguments) Guide data program log path: /var/log/mythtv/mythfilldatabase_wget.log
This note should be removed or updated after wget
is replaced.
syslog Logging
Logging to syslog may be enabled with the argument:
--syslog Set the syslog logging facility. Set to "none" to disable, defaults to none
By default, logging to syslog is disabled. You should only enable syslog logging if you have also configured syslog on your host to handle the MythTV log messages appropriately.
Database Logging
Database logging is enabled by default. It may be disabled with the argument:
--nodblog Disable database logging.
MythTV automatically cleans up the database logging information, to ensure your database does not grow out of control. All database logging information is removed within 2 weeks, so database logging is primarily useful for short-term log access, and should not be considered a valid long-term logging mechanism.
Log file cleanup
When using mythprogramname.log files, see Logrotate - mythbackend or Logrotate - mythfrontend for configuration examples.
When using --logpath /path/to/log_directory
, one file for each run of a program and each of its children will be generated.
As mentioned above, expect to see (for example) /var/log/mythtv/mythbackend.date.pid.log plus
similar entries for mythcommflag, mythmetadatalookup
and mythpreviewgen
.
Since this will create a lot of files in the logging directory, cleanup is strongly recommended.
Existing entries in logrotate
files can be removed and be replaced by cron entries.
#!/bin/sh find /var/log/mythtv -type f -mtime +1 -name "mythpreviewgen.*.log" -delete find /var/log/mythtv -type f -mtime +1 -name "mythcommflag.*.log" -delete find /var/log/mythtv -type f -mtime +1 -name "mythmetadatalookup.*.log" -delete find /var/log/mythtv -type f -mtime +6 -name "mythbackend.*.log" -delete find /var/log/mythtv -type f -mtime +4 -name "mythfrontend.*.log" -delete find /var/log/mythtv -type f -mtime +7 -name "mythfilldatabase.*.log" -delete
The above will remove mythpreviewgen, mythcommflag
and mythmetadatalookup
log files that are one day old.
mythbackend
log files get removed after 6 days etc.
If you prefer to archive your logs, the -delete
expression above can be
replaced with an -exec
expression, for example:
-exec /usr/local/sbin/MythTVLogArchive.sh {} \;
The script could be as basic as: