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Logging is one of the most important aspects of a production-grade server. A properly configured logging system is vital for identifying errors, security threats and usage patterns.

See the following topics for details:


Log types in WSO2 products

Listed below are the various log types that are used in WSO2 products.

Separate log files are created for each of the log types given below in the <PRODUCT_HOME>/repository/logs directory.

  • Carbon logs: All WSO2 products are shipped with log4j logging capabilities that generate administrative activities and server side logs. The Carbon log is a log file that covers all the management features of products. Carbon logs are configured in the log4j.properties  file (stored in the  <PRODUCT_HOME>/repository/conf  directory).  

    Java logging and Log4j integration: In addition to the logs from libraries that use Log4j, all logs from libraries (such as, Tomcat, Hazelcast and more) that use Java logging framework are also visible in the same log files. That is, when Java logging is enabled in Carbon, only the Log4j appenders will write to the log files. If the Java Logging Handlers have logs, these logs will be delegated to the log events of the corresponding Log4j appenders. A Pub/Sub registry pattern implementation has been used in the latter mentioned scenario to plug the handlers and appenders. The following default log4j appenders in the log4j.properties file are used for this implementation:

    • org.wso2.carbon.logging.appenders.CarbonConsoleAppender
    • org.wso2.carbon.logging.appenders.CarbonDailyRollingFileAppender 
  • Audit logs:  Audit logs are used for tracking the sequence of actions that affect a particular task carried out in the server. These are also configured in the  log4j.properties  file (stored in the  <PRODUCT_HOME>/repository/conf  directory).
  • HTTP access logs: HTTP requests/responses are logged in access log(s) to monitor your application's usage, such as the persons who access it, how many hits it receives, the errors etc. These logs are configured in the catalina-server.xml file (stored in the <PRODUCT_HOME>/repository/conf/tomcat/ directory).
  • Trace logs: These are used for tracing the behavior of services. Trace logs are configured in the log4j.properties  file (stored in the  <PRODUCT_HOME>/repository/conf  directory).
  • Patch logs:  This log contains details related to patches applied to the product. This log cannot be customized. See WSO2 Patch Application Process for more information.
  • Product-specific logs: Each WSO2 product may generate other log files in addition to the Carbon logs, Audit logs, HTTP access logs and Patch logs. See the product's documentation for descriptions of these log files and instructions on how to configure and use them.

Configuring products for log monitoring

See the following information on configuring Carbon logs, Audit logs , HTTP access logs, and Trace logs for your WSO2 product.

  • Configuring Carbon logs

    You can easily configure Carbon logs using the management console of your product, or you can manually edit the log4j.properties file. It is recommended to use the management console to configure logging because all changes made to log4j through the management console persists in the WSO2 Registry. Therefore, those changes will be available after the server restarts and will get priority over what is defined in the log4j.properties file. Also, note that the logging configuration you define using the management console will apply at run time.  However, if you modify the log4j.properties file and restart the server, the earlier log4j configuration that persisted in the registry will be overwritten. There is also an option in the management console to restore the original log4j configuration from the log4j.properties file.   

    Identifying forged messages:From Carbon 4.4.3 onwards, it is possible to use a UUID in log messages so that any forged messages can be easily identified.  The UUID is logged using a new conversion character ‘K’ in the log pattern layout.  By default, the UUID will be generated every time the server starts. However, you can configure your server to generate the UUID more or less frequently, by specifying an exact time interval in the log4j.properties file.

    See the following topics for instructions:

  • Configuring Audit logs

    Audit logs are enabled in WSO2 products by default. You can change the following default configuration by manually updating the the log4j.properties file. 

    log4j.logger.AUDIT_LOG=INFO, AUDIT_LOGFILE
     
    # Appender config to AUDIT_LOGFILE
    log4j.appender.AUDIT_LOGFILE=org.wso2.carbon.utils.logging.appenders.CarbonDailyRollingFileAppender
    log4j.appender.AUDIT_LOGFILE.File=${carbon.home}/repository/logs/audit.log
    log4j.appender.AUDIT_LOGFILE.Append=true
    log4j.appender.AUDIT_LOGFILE.layout=org.wso2.carbon.utils.logging.TenantAwarePatternLayout
    log4j.appender.AUDIT_LOGFILE.layout.ConversionPattern=[%d] %P%5p {%c}- %x %m %n
    log4j.appender.AUDIT_LOGFILE.layout.TenantPattern=%U%@%D [%T] [%S]
    log4j.appender.AUDIT_LOGFILE.threshold=INFO
    log4j.additivity.AUDIT_LOG=false
  • Configuring HTTP access logs

    See HTTP Access Logging for instructions on how to configure and use HTTP access logs.

  • Configuring Trace logs

    Trace logs are disabled by default in WSO2 products. To enable Trace logs, the preferred log4j appender should be configured with TRACE level as the threshold in the log4j.properties file. For example, if CARBON_LOGFILE is the log4j appender, the threshold level should be changed to TRACE as shown below. The default threshold is set to DEBUG.

    log4j.appender.CARBON_LOGFILE.threshold=TRACE

Listed below are the Log4j log level that can be configured for Carbon logs, Audit logs and Trace logs in the log4j.properties file:

 

Level

Description

OFF

The highest possible log level, which is intended for disabling logging.

FATAL

Indicates severe errors that cause premature termination. These logs are expected to be immediately visible on a status console.

ERROR

Indicates other runtime errors or unexpected conditions. These logs are expected to be immediately visible on a status console.

WARN

Indicaes the use of deprecated APIs, poor use of API, possible errors, and other runtime situations that are undesirable or unexpected but not necessarily wrong. These logs are expected to be immediately visible on a status console.

INFO

Indicates important runtime events, such as server startup/shutdown. These logs are expected to be immediately visible on a console. It is recommended to keep these logs to a minimum.

DEBUG

Provides detailed information on the flow through the system. This information is expected to be written to logs only. Generally, most lines logged by your application should be written as DEBUG logs.

TRACE

Provides detailed information, which are expected to be written to logs only.

Managing log growth

See the following content on managing the growth of Carbon logs and Audit logs:

Managing the growth of Carbon logs

Log growth (in Carbon logs) can be managed by the following configurations in the <PRODUCT_HOME>/repository/conf/ log4j.properties file.

  • Configurable log rotation: By default, log rotation is on a daily basis.
  • Log rotation based on time as opposed to size: This helps to inspect the events that occurred during a specific time.
  • Log files are archived to maximise the use of space.

The log4j-based logging mechanism uses appenders to append all the log messages into a file. That is, at the end of the log rotation period, a new file will be created with the appended logs and archived. The name of the archived log file will always contain the date on which the file is archived. 

Limiting the size of Carbon log files

You can limit the size of the  <PRODUCT_HOME>/repository/logs/wso2carbon.log file by following the steps given below. This is useful if you want to archive the logs and get backups periodically.

  1. Change the log4j.appender.CARBON_LOGFILE=org.wso2.carbon.utils.logging.appenders.CarbonDailyRollingFileAppenderappender in the <PRODUCT_HOME>/repository/conf/ log4j.properties file as follows:

    log4j.appender.CARBON_LOGFILE=org.apache.log4j.RollingFileAppender
  2. Add the following two properties under RollingFileAppender

    • log4j.appender.CARBON_LOGFILE.MaxFileSize=10MB 

    • log4j.appender.CARBON_LOGFILE.MaxBackupIndex=20

    If the size of the log file is exceeding the value defined in the MaxFileSize property, the content is copied to a backup file and the logs are continued to be added to a new empty log file. The MaxBackupIndex property makes the Log4j maintain a maximum number of backup files for the logs.

Limiting the size of audit log files

In WSO2 servers, audit logs are enabled by default. We can limit the audit log files with the following configuration:

  1. Change the log4j.appender.AUDIT_LOGFILE=org.wso2.carbon.logging.appenders.CarbonDailyRollingFileAppenderappender in the <PRODUCT_HOME>/repository/conf/log4j.properties file as follows: log4j.appender.AUDIT_LOGFILE=org.apache.log4j.RollingFileAppender
  2. Add the following two properties under RollingFileAppender:
    • log4j.appender.AUDIT_LOGFILE.MaxFileSize=10MB 
    • log4j.appender.AUDIT_LOGFILE.MaxBackupIndex=20

Monitoring logs

In each WSO2 product, users can configure and adjust the logging levels for each type of activity/transaction. There are several ways to view and monitor the logs:

  • Carbon logs (system logs and application logs) of a running Carbon instance can be monitoring using the management console.
  • Carbon logs, as well as HTTP access logs will be printed on the command terminal that open when you execute the product startup script.
  • Alternatively, all log files can be viewed from the <PRODUCT_HOME>/repository/logs folder. This folder contains Audit logs, HTTP access logs as well as the Carbon logs in separate log files with date stamps. Note that older Carbon logs are archived in the wso2carbon.log file.
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