= logback.xml file

The `logback.xml` configuration file can optionally set logging levels
for the logs written to `system.log` and `debug.log`. The logging levels
can also be set using `nodetool setlogginglevels`.

== Options

=== `appender name="<appender_choice>"...</appender>` 

Specify log type and settings. Possible appender names are: `SYSTEMLOG`,
`DEBUGLOG`, `ASYNCDEBUGLOG`, and `STDOUT`. `SYSTEMLOG` ensures that WARN
and ERROR message are written synchronously to the specified file.
`DEBUGLOG` and `ASYNCDEBUGLOG` ensure that DEBUG messages are written
either synchronously or asynchronously, respectively, to the specified
file. `STDOUT` writes all messages to the console in a human-readable
format.

*Example:* <appender name="SYSTEMLOG"
class="ch.qos.logback.core.rolling.RollingFileAppender">

=== `<file> <filename> </file>` 

Specify the filename for a log.

*Example:* <file>$\{cassandra.logdir}/system.log</file>

=== `<level> <log_level> </level>`

Specify the level for a log. Part of the filter. Levels are: `ALL`,
`TRACE`, `DEBUG`, `INFO`, `WARN`, `ERROR`, `OFF`. `TRACE` creates the
most verbose log, `ERROR` the least.

[NOTE]
.Note
====
Note: Increasing logging levels can generate heavy logging output on
a moderately trafficked cluster. You can use the
`nodetool getlogginglevels` command to see the current logging
configuration.
====

*Default:* INFO

*Example:* <level>INFO</level>

=== `<rollingPolicy class="<rolling_policy_choice>" <fileNamePattern><pattern_info></fileNamePattern> ... </rollingPolicy>`

Specify the policy for rolling logs over to an archive.

*Example:* <rollingPolicy
class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">

=== `<fileNamePattern> <pattern_info> </fileNamePattern>`

Specify the pattern information for rolling over the log to archive.
Part of the rolling policy.

*Example:*
<fileNamePattern>$\{cassandra.logdir}/system.log.%d\{yyyy-MM-dd}.%i.zip</fileNamePattern>

=== `<maxFileSize> <size> </maxFileSize>`

Specify the maximum file size to trigger rolling a log. Part of the
rolling policy.

*Example:* <maxFileSize>50MB</maxFileSize>

=== `<maxHistory> <number_of_days> </maxHistory>`

Specify the maximum history in days to trigger rolling a log. Part of
the rolling policy.

*Example:* <maxHistory>7</maxHistory>

=== `<encoder> <pattern>...</pattern> </encoder>`

Specify the format of the message. Part of the rolling policy.

*Example:* <maxHistory>7</maxHistory> *Example:* <encoder>
<pattern>%-5level [%thread] %date\{ISO8601} %F:%L - %msg%n</pattern>
</encoder>

=== Contents of default `logback.xml`

[source,XML]
----
<configuration scan="true" scanPeriod="60 seconds">
  <jmxConfigurator />

  <!-- No shutdown hook; we run it ourselves in StorageService after shutdown -->

  <!-- SYSTEMLOG rolling file appender to system.log (INFO level) -->

  <appender name="SYSTEMLOG" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
  <level>INFO</level>
    </filter>
    <file>${cassandra.logdir}/system.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
      <!-- rollover daily -->
      <fileNamePattern>${cassandra.logdir}/system.log.%d{yyyy-MM-dd}.%i.zip</fileNamePattern>
      <!-- each file should be at most 50MB, keep 7 days worth of history, but at most 5GB -->
      <maxFileSize>50MB</maxFileSize>
      <maxHistory>7</maxHistory>
      <totalSizeCap>5GB</totalSizeCap>
    </rollingPolicy>
    <encoder>
      <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern>
    </encoder>
  </appender>

  <!-- DEBUGLOG rolling file appender to debug.log (all levels) -->

  <appender name="DEBUGLOG" class="ch.qos.logback.core.rolling.RollingFileAppender">
    <file>${cassandra.logdir}/debug.log</file>
    <rollingPolicy class="ch.qos.logback.core.rolling.SizeAndTimeBasedRollingPolicy">
      <!-- rollover daily -->
      <fileNamePattern>${cassandra.logdir}/debug.log.%d{yyyy-MM-dd}.%i.zip</fileNamePattern>
      <!-- each file should be at most 50MB, keep 7 days worth of history, but at most 5GB -->
      <maxFileSize>50MB</maxFileSize>
      <maxHistory>7</maxHistory>
      <totalSizeCap>5GB</totalSizeCap>
    </rollingPolicy>
    <encoder>
      <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern>
    </encoder>
  </appender>

  <!-- ASYNCLOG assynchronous appender to debug.log (all levels) -->

  <appender name="ASYNCDEBUGLOG" class="ch.qos.logback.classic.AsyncAppender">
    <queueSize>1024</queueSize>
    <discardingThreshold>0</discardingThreshold>
    <includeCallerData>true</includeCallerData>
    <appender-ref ref="DEBUGLOG" />
  </appender>

  <!-- STDOUT console appender to stdout (INFO level) -->

  <appender name="STDOUT" class="ch.qos.logback.core.ConsoleAppender">
    <filter class="ch.qos.logback.classic.filter.ThresholdFilter">
      <level>INFO</level>
    </filter>
    <encoder>
      <pattern>%-5level [%thread] %date{ISO8601} %F:%L - %msg%n</pattern>
    </encoder>
  </appender>

  <!-- Uncomment bellow and corresponding appender-ref to activate logback metrics
  <appender name="LogbackMetrics" class="com.codahale.metrics.logback.InstrumentedAppender" />
   -->

  <root level="INFO">
    <appender-ref ref="SYSTEMLOG" />
    <appender-ref ref="STDOUT" />
    <appender-ref ref="ASYNCDEBUGLOG" /> <!-- Comment this line to disable debug.log -->
    <!--
    <appender-ref ref="LogbackMetrics" />
    -->
  </root>

  <logger name="org.apache.cassandra" level="DEBUG"/>
  <logger name="com.thinkaurelius.thrift" level="ERROR"/>
</configuration>
----