16.2. Logging Configuration
Overview
The logging system is configured by a combination of two OSGi Admin PIDs and one configuration file:
etc/system.properties—the configuration file that sets the logging level during the container’s boot process. The file contains a single property, org.ops4j.pax.logging.DefaultServiceLog.level, that is set toERRORby default.org.ops4j.pax.logging—the PID used to configure the logging back end service. It sets the logging levels for all of the defined loggers and defines the appenders used to generate log output. It uses standard Log4j configuration. By default, it sets the root logger's level toINFOand defines two appenders: one for the console and one for the log file.NoteThe console's appender is disabled by default. To enable it, addlog4j.appender.stdout.append=trueto the configuration For example, to enable the console appender in a standalone container, you would use the following commands:JBossFuse:karaf@root>config:edit org.ops4j.pax.loggingJBossFuse:karaf@root>config:propappend log4j.appender.stdout.append trueJBossFuse:karaf@root>config:updateorg.apache.karaf.log.cfg—configures the output of the log console commands.
The most common configuration changes you will make are changing the logging levels, changing the threshold for which an appender writes out log messages, and activating per bundle logging.
Changing the log levels
The default logging configuration sets the logging levels so that the log file will provide enough information to monitor the behavior of the runtime and provide clues about what caused a problem. However, the default configuration will not provide enough information to debug most problems.
The most useful logger to change when trying to debug an issue with Red Hat JBoss Fuse is the root logger. You will want to set its logging level to generate more fine grained messages. To do so you change the value of the
org.ops4j.pax.logging PID's log4j.rootLogger property so that the logging level is one of the following:
TRACEDEBUGINFOWARNERRORFATALNONE
Example 16.1, “Changing Logging Levels” shows the commands for setting the root loggers log level in a standalone container.
Example 16.1. Changing Logging Levels
JBossFuse:karaf@root>config:edit org.ops4j.pax.loggingJBossFuse:karaf@root>config:propset log4j.rootLogger "DEBUG, out, osgi:VmLogAppender"JBossFuse:karaf@root>config:update
Changing the appenders' thresholds
When debugging a problem in JBoss Fuse you may want to limit the amount of logging information that is displayed on the console, but not the amount written to the log file. This is controlled by setting the thresholds for each of the appenders to a different level. Each appender can have a
log4j.appender.appenderName.threshold property that controls what level of messages are written to the appender. The appender threshold values are the same as the log level values.
Example 16.2, “Changing the Log Information Displayed on the Console” shows an example of setting the root logger to
DEBUG but limiting the information displayed on the console to WARN.
Example 16.2. Changing the Log Information Displayed on the Console
JBossFuse:karaf@root>config:edit org.ops4j.pax.loggingJBossFuse:karaf@root>config:propset log4j.rootLogger "DEBUG, out, osgi:VmLogAppender"JBossFuse:karaf@root>config:propappend log4j.appender.stdout.threshold WARNJBossFuse:karaf@root>config:update
Logging per bundle
It is possible to reconfigure JBoss Fuse logging so that it writes one log file for each bundle, instead of writing all of the log messages into a single log file. This feature is enabled by adding the Log4j
sift appender to the Log4j root logger as shown in Example 16.3, “Enabling Per Bundle Logging”.
Example 16.3. Enabling Per Bundle Logging
JBossFuse:karaf@root>config:edit org.ops4j.pax.loggingJBossFuse:karaf@root>config:propset log4j.rootLogger "INFO, out, sift, osgi:VmLogAppender"JBossFuse:karaf@root>config:update
After restarting the container, you can see that each BundleName bundle now has its own log file, located at
data/log/BundleName.log.
This is the behavior you will see with the default sift appender settings. You can edit this behavior using the sift appender configuration settings in
org.ops4j.pax.logging.cfg.
Logging History
When JBoss Fuse is stopped, the Karaf log is saved in
~/.karaf/karaf.history. JBoss Fuse can be configured to prevent the history from being saved each time.
Procedure 16.1. Stop JBoss Fuse saving Logging History on shutdown.
- Stop JBoss Fuse.
- Edit
$FUSE_HOME/etc/system.properties. - Uncomment the line that says
# karaf.shell.history.maxSize = 0. - Restart JBoss Fuse
~/.karaf/karaf.history will still be created, but it will always have a size of 0, and will be empty.
