Brooklyn uses the SLF4J logging facade, which allows use of many popular frameworks including logback, java.util.logging and log4j.

The convention for log levels is as follows:

  • ERROR and above: exceptional situations which indicate that something has unexpectedly failed or some other problem has occurred which the user is expected to attend to
  • WARN: exceptional situations which the user may which to know about but which do not necessarily indicate failure or require a response
  • INFO: a synopsis of activity, but which should not generate large volumes of events nor overwhelm a human observer
  • DEBUG and lower: detail of activity which is not normally of interest, but which might merit closer inspection under certain circumstances.

Loggers follow the package.ClassName naming standard.

The default logging is to write INFO+ messages to brooklyn.info.log, and DEBUG+ to brooklyn.debug.log. Each is a rolling log file, where the past 10 files will be kept. INFO level, and above, messages will be logged to the karaf console. Use the log: commands in the karaf client, e.g. log:tail, to read these messages.

Standard Configuration

A org.ops4j.pax.logging.cfg file is included in the etc/ directly of the Brooklyn distro; this is read by brooklyn at launch time. Changes to the logging configuration, such as new appenders or different log levels, can be made directly in this file.

Karaf logging is highly configurable. For example enable the sift appender to log to separate log files for each bundle as described here: Advanced configuration

A full explanation of logging in karaf is available here.

Log File Backup

This sub-section is a work in progress; feedback from the community is extremely welcome.

The default rolling log files can be backed up periodically, e.g. using a CRON job.

Note however that the rolling log file naming scheme will rename the historic zipped log files such that brooklyn.debug-1.log.zip is the most recent zipped log file. When the current brooklyn.debug.log is to be zipped, the previous zip file will be renamed brooklyn.debug-2.log.zip. This renaming of files can make RSYNC or backups tricky.

An option is to covert/move the file to a name that includes the last-modified timestamp. For example (on mac):

TIMESTAMP=`stat -f '%Um' $LOG_FILE`
mv $LOG_FILE /path/to/archive/brooklyn.debug-$TIMESTAMP.log.zip

Logging aggregators

Integration with systems like Logstash and Splunk is possible using standard log4j configuration. Log4j can be configured to write to syslog using the SyslogAppender which can then feed its logs to Logstash.

For More Information

The following resources may be useful when configuring logging:

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