# Trac Logging
[[TracGuideToc]]

Trac supports logging of system messages using the standard [logging module](http://docs.python.org/library/logging.html) that comes with Python.

Logging is configured in the `[logging]` section in [wiki:TracIni#logging-section trac.ini].

## Supported Logging Methods

The log method is set using the `log_type` option in [wiki:TracIni#logging-section trac.ini], which takes any of the following values:

 **none*:: Suppress all log messages.
 **file**:: Log messages to a file, specified with the `log_file` option in [wiki:TracIni#logging-section trac.ini]. Relative paths in `log_file` are resolved relative to the `log` directory of the environment.
 **stderr**:: Output all log entries to console ([wiki:TracStandalone tracd] only).
 **syslog**:: (UNIX) Send all log messages to the local syslogd via named pipe `/dev/log`. By default, syslog will write them to the file /var/log/messages.
 **eventlog**:: (Windows) Use the system's NT Event Log for Trac logging.

## Log Levels

The verbosity level of logged messages can be set using the `log_level` option in [wiki:TracIni#logging-section trac.ini]. The log level defines the minimum level of urgency required for a message to be logged, and those levels are:

 **CRITICAL**:: Log only the most critical (typically fatal) errors.
 **ERROR**:: Log failures, bugs and errors.
 **WARN**:: Log warnings, non-interrupting events.
 **INFO**:: Diagnostic information, log information about all processing.
 **DEBUG**:: Trace messages, profiling, etc.

Additionally, you can  enable logging of SQL statements at debug level. This is turned off by default, as it's very verbose. Set `[trac] debug_sql = yes` in TracIni to activate.

## Log Format

The output format for log entries can be specified through the `log_format` option in [trac.ini]. The format is a string which can contain any of the [http://docs.python.org/library/logging.html#logrecord-attributes Python logging Formatter variables](wiki:TracIni#logging-section). Additonally, the following Trac-specific variables can be used:
 **$(basename)s**:: The last path component of the current environment.
 **$(path)s**:: The absolute path for the current environment.
 **$(project)s**:: The originating project's name.

Note that variables are identified using a dollar sign (`$(...)s`) instead of percent sign (`%(...)s`).

The default format is:
```#!ini
log_format = Trac[$(module)s] $(levelname)s: $(message)s
```

In a multi-project environment where all logs are sent to the same place (e.g. `syslog`), it makes sense to add the project name. In this example we use `basename` since that can generally be used to identify a project:
```#!ini
log_format = Trac[$(basename)s:$(module)s] $(levelname)s: $(message)s
```

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See also: TracIni, TracGuide, TracEnvironment