log4j APL Logging Configurations

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

Configuration Files

There is a configuration file called apl-log4j.properties containing default settings located in the $MZ_HOME/etc/logging directory that is used to specify the path of log files, log filtering rules, log level and formatting. If you want to use different settings for different Execution Contexts, this file can be copied and renamed to <ec-name>-apl-log4j.properties where you can configure different settings for the specified EC.

To provide some examples and templates, there are a number of pre-existing files with the name apl-log4j-<log level name>.properties, for example apl-log4j-trace.properties, which you can use to either copy properties from, or make a copy of the whole file and rename it to <ec-name>-apl-log4j.properties. 

Example. Configuration filenames

Default configuration file:


EC specific configuration file for ec1:


Copying the default configuration file into an EC specific configuration file:

$cp apl-log4j.properties ec1-apl-log4j.properties

Copying a template configuration file into an EC specific configuration file:
$cp apl-log4j-trace.properties ec1-apl-log4j.properties

The following template 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.

Example. Configuration file contents

log4j.rootLogger=ALL, a
log4j.appender.a.layout.MdcFieldsToLog=pico, workflow, agent, tag

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
  • WARN
  • INFO
  • 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 in files that are started, stopped and stored in JSON formatted files in the $MZ_HOME/log directory in regular intervals. 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).


There are two different types of appenders; DRRollingFileAppender och DRRollingMultiFileAppender


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


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.

Examples Appender Configurations

# Default
log4j.appender.Default.layout.ConversionPattern=[%d{dd MMM yyyy HH:mm:ss,SSS}];[%-5p];[pico=%X{pico}];[%t];[tag=%X{tag}];[%c]:%m%n
log4j.logger.Default=TRACE, Default

The appender named Default will write a single file for all workflows contained under the Default folder.

log4j.appender.PRIMARY.layout.ConversionPattern=[%d{dd MMM yyyy HH:mm:ss,SSS}];[%-5p];[pico=%X{pico}];[%t];[tag=%X{tag}];[%c]:%m%n
log4j.logger.RT_Folder.RT_TEST_WF=TRACE, PRIMARY

The appender named Primary will create multiple files; one for each workflow instance based on the RT_Folder.RT_TEST_WF workflow.

log4j.appender.SECONDARY.layout.ConversionPattern=[%d{dd MMM yyyy HH:mm:ss,SSS}];[%-5p];[pico=%X{pico}];[%t];[tag=%X{tag}];[%c]:%m%n
log4j.logger.RT_Folder.RT_TEST_WF=TRACE, SECONDARY

The appender Secondary will  create a single file for each workflow instance based on the RT_Folder.RT_TEST_WF workflow. The file will take the name of the first workflow instance it encounters, for example "RT_Folder.RT_TEST_WF.workflow_1" 


You can change the maximum file size and the number of backup files by adding the following lines:

You can add a filtering rule by adding the line log4j.logger.<configuration name>=<log level>. This is useful when you want to set different log levels for specific folders or configurations.

Example. Sets the general log level to ERROR and to DEBUG for the agent named agent_1

log4j.rootLogger=ERROR, a 

If you want to apply the filtering rule to all APL configurations in the default folder, change the last line in the previous example to log4j.logger.Default=DEBUG.


For performance reasons it is recommended to use the DRRollingFileAppender and configure individual appenders for each workflow. Only use the DRRollingMultiFileAppender if you need individual files on a workflow instance level.

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

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 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.

Example. Log file in JSON format

{"timestamp":"2015-12-20:22:44:10 UTC","level":"DEBUG","thread":"Default.logtestwf.workflow_1: TCP_IP_1_1","category":"Default.logtestwf.workflow_1.Analysis_1","message":"In consume","pico":"EC1","workflow":"Default.logtestwf.workflow_1","agent":"Analysis_1"}

The fields in the log output are described below.


The time when the message was logged. The UTC timezone and international standard date and time notation is used by default. 
You can specify the date format by adding the following line in the configuration file:

log4j.appender.a.layout.DateFormat=<Java SimpleDateFormat pattern>

For information about how to use SimpleDateFormat patterns, see:

levelThe log level i e FATAL, ERRORWARN, INFO, DEBUG, or TRACE.
threadThe name of the workflow thread.
categoryThe logged configuration. This field contains the category class of the appender that is defined in the configuration file.
messageThe log message is specified in the APL command.
picoThe name of the Execution Context.


The ECs must be restarted if you manually delete or rename active log files or backup log files.


  If the log files are not generated as expected, review the EC logs. Your configuration files may contain errors.