includes a log4j extension that enables the generation of customized logs from agents configured with APL. This section describes how to configure these logs to meet deployment-specific requirements.

Configuration Files

The configuration files are used to specify the path of log files, log filtering rules, log level, and formatting. These files must be stored in $MZ_HOME/etc/logging and named apl-log4j-<log level name>.properties or <ec-name>-apl-log4j-<log level name>.properties. Use <ec-name> prefixed filenames when you want to use different log settings for different Execution Contexts.

The following configuration files are included by default:

• apl-log4j-off.properties

• apl-log4j-fatal.properties

• apl-log4j-error.properties

• apl-log4j-warn.properties

• apl-log4j-info.properties

• apl-log4j-debug.properties

• apl-log4j-trace.properties

• apl-log4j-all.properties

The files listed above have a different log level setting but are otherwise identical.

The content of the files defines the logging.

The first line in the example above sets the log level and declares an "appender" named 'a'. The available log levels are listed below in order of severity, from highest to lowest:

• OFF

• FATAL

• ERROR

• WARN

• INFO

• DEBUG

• TRACE

• ALL

Messages of the same or higher severity than the selected level are logged. For instance, if the configured log level is WARN, messages with the severity ERROR and FATAL will be logged as well. The other settings above mean that messages are logged and stored in rotated and JSON formatted files in the $MZ_HOME/log directory. When an active log file has reached its maximum size, it is backed up and stored with a number suffix. A new active log file is then created. The default maximum size is 10 MB, and the default number of backup files is one (1).

Appenders

There are two different types of appenders; DRRollingFileAppender och DRRollingMultiFileAppender. 

DRRollingFileAppender 

Writes to a single defined file based on the log4j.appender.<appender name>.file property

DRRollingMultiFileAppender 

Writes one file for each workflow instance it encounters based on the log4j.appender.<appender name>.file

Which workflows are written into which appender is based on the log4j.logger.<class name> property.

For more information about available settings, see the log4j documentation at https://logging.apache.org/log4j/1.2/manual.html.

mzsh Command

You can select the active logging configuration for each Execution Context by using the mzsh command loglevel.

usage: apl-loglevel [ display | set <level> ] <ec-names> 

The level argument to the command is based on the corresponding configuration filename in $MZ_HOME/etc/logging. For instance, the command below will activate the configuration in ec1-apl-log4j-myloglevel.properties  on the Execution Context named ec1 and ec2-apl-log4j-myloglevel.properties on ec2. If any of these files cannot be found, the command will (if possible) apply the settings of a file without the Execution Context prefix, i e apl-log4j-myloglevel.properties.

You can view the configured log directory and refresh interval with apl-loglevel display.

The log refresh interval is set to 1000 ms by default. You can change this value by setting the Platform property mz.logging.refreshinterval.

When you activate a configuration the contents of the corresponding file is copied to <ec name>-apl-log4j.properties. Any changes in this file will become effective at the next refresh interval.

APL Commands

The following functions are used to trigger logging within any of the function blocks in APL:

• void log.fatal(any, any)

• void log.error(any, any)

• void log.warn(any, any)

• void log.info(any, any)

• void log.debug(any, any)

• void log.trace(any, any)

For more information about these functions, see 23. Log and Notification Functions in the APL Reference Guide.

Log Output

The output log files are stored in the directory specified in the active logging configuration.

The fields in the log output are described below.