If the directory/file paths specified in this guide do not exist in your WSO2 product, see Directory Structure of WSO2 Products to locate the paths applicable to your product.
Monitoring Logs - Administration Guide 4.4.x - WSO2 Documentation
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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 (wso2carbon.log) is a log file that covers all the management features of a product. 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 on the server. These are also configured in the  log4j.properties  file.
  • HTTP access logs: HTTP requests/responses are logged in access logs to monitor the activities related to an application's usage. These logs are configured in the catalina-server.xml file (stored in the <PRODUCT_HOME>/repository/conf/tomcat/ directory).
  • Patch logs: These logs contain details related to patches applied to the product. Patch logs cannot be customized. See WSO2 Patch Application Process for more information.
  • Service/Event logs: These are logs that are enabled in some WSO2 products for tracing services and events using a separate log file (wso2-<product>-trace.log). If server/event tracing logs are used in your WSO2 product, you can configure them in the log4j.properties file.
  • Product-specific logs: Each WSO2 product may generate other log files in addition to the Carbon logs, Audit logs, HTTP access logs, Patch logs and Service/Event 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 Service/Event 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. The log levels that can be configured are listed below.

    Identifying forged messages: 

    The log pattern defines the output format of the log file. From Carbon 4.4.3 onwards, the conversion character 'K' can be used in the pattern layout to log a UUID. For example, the log pattern can be [%K] [%T] [%S] [%d] %P%5p {%c} - %x %m {%c}%n, where [%K] is the UUID.

    The UUID can be used for identifying forged messages in the log. By default, the UUID will be generated every time the server starts. If required, you can configure the UUID regeneration period by manually adding the following property to the log4j.properties file (stored in the <PRODUCT_HOME>/repository/conf directory):

    log4j.appender.CARBON_LOGFILE.layout.LogUUIDUpdateInterval=<number_of_hours>

    Carbon logs in WSO2 Data Analytics Server (WSO2 DAS)

    Carbon logs are configured in the log4j.properties file (stored in the <PRODUCT_HOME>/repository/conf directory) for all WSO2 products. However, WSO2 DAS generates some additional Carbon logs (which will be stored in the same Carbon log file) that should be separately configured by creating a new log4j.properties file in the <DAS_HOME>/repository/conf/analytics/spark  directory. Note: To create this file, you need to rename the log4j.properties.template file that is available in the <DAS_HOME>/repository/conf/analytics/spark directory to log4j.properties. 

    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. The log levels that can be configured are listed below.

    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 Service/Event tracing logs
    A separate log file for tracing services/events are enabled for certain WSO2 products in the log4j.properties file using a specific appender. These logs are published to a file named wso2-<product>-trace.log. See the table given below for instructions relevant to your product:

    ProductDescription
    WSO2 DAS

    Event tracing logs are enabled in WSO2 DAS using the EVENT_TRACE_LOGGER appender as shown below (Click Message tracing log configuration). This log file stores logs related to events in WSO2 DAS. By default, this appender uses the root log level, which is INFO. You can override the root log level by giving a specific log level for the appender as explained here.

     Message tracing log configuration
    log4j.category.EVENT_TRACE_LOGGER=INFO, EVENT_TRACE_APPENDER, EVENT_TRACE_MEMORYAPPENDER
    log4j.additivity.EVENT_TRACE_LOGGER=false
    log4j.appender.EVENT_TRACE_APPENDER=org.apache.log4j.DailyRollingFileAppender
    log4j.appender.EVENT_TRACE_APPENDER.File=${carbon.home}/repository/logs/${instance.log}/wso2-das-trace${instance.log}.log
    log4j.appender.EVENT_TRACE_APPENDER.Append=true
    log4j.appender.EVENT_TRACE_APPENDER.layout=org.apache.log4j.PatternLayout
    log4j.appender.EVENT_TRACE_APPENDER.layout.ConversionPattern=%d{HH:mm:ss,SSS} [%X{ip}-%X{host}] [%t] %5p %c{1} %m%n
    # The memory appender for trace logger
    log4j.appender.EVENT_TRACE_MEMORYAPPENDER=org.wso2.carbon.utils.logging.appenders.MemoryAppender
    log4j.appender.EVENT_TRACE_MEMORYAPPENDER.bufferSize=2000
    log4j.appender.EVENT_TRACE_MEMORYAPPENDER.layout=org.apache.log4j.PatternLayout
    log4j.appender.EVENT_TRACE_MEMORYAPPENDER.layout.ConversionPattern=%d{HH:mm:ss,SSS} [%X{ip}-%X{host}] [%t] %5p %m%n

Setting the Log4j log level

The log level can be set specifically for each appender in the log4j.properties file by setting the threshold value. If a log level is not specifically given for an appender as explained below, the root log level (INFO) will apply to all appenders by default.

For example, shown below is how the log level is set to DEBUG for the CARBON_LOGFILE appender (Carbon log):

log4j.appender.CARBON_LOGFILE.threshold=DEBUG

Listed below are the log levels that can be configured:


Level

Description

OFF

The highest possible log level. This is intended for disabling logging.

FATAL

Indicates server errors that cause premature termination. These logs are expected to be immediately visible on the command line that you used for starting the server.

ERROR

Indicates other runtime errors or unexpected conditions. These logs are expected to be immediately visible on the command line that you used for starting the server.

WARN

Indicates 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 the command line that you used for starting the server.

INFO

Indicates important runtime events, such as server startup/shutdown. These logs are expected to be immediately visible on the command line that you used for starting the server. 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 additional details on the behavior of events and services. This information is 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 time stamps. Note that older Carbon logs are archived in the wso2carbon.log file.
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