Log4j2 Appender¶

Custom appender for log4j2 to track the number of log messages reported.

Getting Started¶

To use it simply add a dependency:

com.netflix.spectator:spectator-ext-log4j2:${version}

Then in your application initialization:

Registry registry = ...
SpectatorAppender.addToRootLogger(
    registry,             // Registry to use
    "spectator",          // Name for the appender
    false);               // Should stack traces be ignored?

This will add the appender to the root logger and register a listener so it will get re-added if the configuration changes. You can also use the appender by specifying it in the log4j2 configuration, but this will cause some of the loggers in Spectator to get created before log4j is properly initialized and result in some lost log messages. With that caveat in mind, if you need the additional flexibility of using the configuration then specify the Spectator appender:

<?xml version="1.0" encoding="UTF-8"?>
<Configuration monitorInterval="5" status="warn">
  <Appenders>
    <Spectator name="root"/>
  </Appenders>
  <Loggers>
    <Root level="debug">
      <AppenderRef ref="root"/>
    </Root>
  </Loggers>
</Configuration>

Metrics¶

log4j.numMessages¶

Counters showing the number of messages that have been passed to the appender.

Unit: messages/second

Dimensions:

appender: name of the spectator appender.
loglevel: standard log level of the events.

log4j.numStackTraces¶

Counter for the number of messages with stack traces written to the logs. This will only be collected if the ignoreExceptions flag is set to false for the appender.

Unit: messages/second

Dimensions:

appender: name of the spectator appender.
loglevel: standard log level of the events.
exception: simple class name for the exception that was thrown.
file: file name for where the exception was thrown.