11.3 Configuring Serviceability and Diagnostics
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## 11.3 Configuring Serviceability and Diagnostics

The serviceability features of Virgo allow you to gather and view data and information that you can then use to diagnose problems and failures. Serviceability data includes:

- Service dumps: Contain a snapshot of all the important state from the running Virgo instance when an internal failure or thread deadlock is detected.

  You configure service dumps for Virgo using the org.eclipse.virgo.medic.properties file in the `$SERVER_HOME/config` directory. This file also includes some additional logging configuration.

- Event logs and server/application (trace) logging: Logging support in Virgo is based on Logback. This means that you have complete control over the format of log output and have the complete range of Logback's appenders available for your use.

  You configure logging for Virgo using the serviceability.xml file in the `$SERVER_HOME/config` directory. This file is essentially the Logback `logback.xml` (or `logback-test.xml`) configuration file but renamed for Virgo.

For additional conceptual information about the serviceability subsystem, see Chapter 9, Serviceability and Diagnostics.

### The org.eclipse.virgo.medic.properties File

The `$SERVER_HOME/config/org.eclipse.virgo.medic.properties` file configures Virgo service dumps and whether you want to capture `System.out` and `System.err` output to your application's trace file.

The following table describes the properties you can include in the `$SERVER_HOME/config/org.eclipse.virgo.medic.properties` file. This file configures serviceability properties that Virgo includes in addition to those supplied by the Logback, configured in the `serviceability.xml` file.

Table 11.4. Serviceability Properties

Property | Description
--- | ---
`dump.root.directory` | Specifies the directory to which Virgo writes the service dumps. The directory name is relative to `$SERVER_HOME`.
`log.wrapSysOut` | Specifies whether you want to capture `System.out` output from your applications to the application trace file. The output is logged by Virgo's root logger, which captures `INFO` level and above. Valid values for this property are `true` to capture `System.out` output, or `false` to disable the capture. For more information, see System.out and System.err.
`log.wrapSysErr` | Specifies whether you want to capture `System.err` output from your applications to the application trace file. The output is logged by Virgo's root logger, which captures `INFO` level and above. Valid values for this property are `true` to capture `System.err` output, or `false` to disable the capture. For more information, see System.out and System.err.
`log.jul.consoleHandler` | Specifies whether you want to use the `ConsoleHandler` of Java Util Logging. The default JVM configuration uses the handler to write logs to `System.err`. Valid values for this property are `true` to enable `ConsoleHandler` output, or `false` to disable it. The default value is `false`. For more information, see Java Logging Overview.

### The serviceability.xml File

Logging support in Virgo is based on Logback, which is a successor of the log4j project. The Logback logging framework is faster, more reliable, and easier to use than log4j and certain other logging systems.

You configure logging for Virgo using the `$SERVER_HOME/config/serviceability.xml` file. This file is the standard Logback `logback.xml` or `logback-test.xml` configuration file, but renamed for Virgo.

The following listing shows the default `serviceability.xml` file in a freshly-installed Virgo; see the text after the listing for a brief overview of the file:

    <configuration>

    	<contextListener class="ch.qos.logback.classic.jul.LevelChangePropagator"/>

    	<appender name="SIFTED_LOG_FILE" class="ch.qos.logback.classic.sift.SiftingAppender">
    		<discriminator>
    			<Key>applicationName</Key>
    			<DefaultValue>virgo-server</DefaultValue>
    		</discriminator>
    		<sift>
    			<appender name="${applicationName}_LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    				<file>serviceability/logs/${applicationName}/log.log</file>
    				<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
    					<FileNamePattern>serviceability/logs/${applicationName}/log_%i.log</FileNamePattern>
    					<MinIndex>1</MinIndex>
    					<MaxIndex>4</MaxIndex>
    				</rollingPolicy>
    				<triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
    					<MaxFileSize>10MB</MaxFileSize>
    				</triggeringPolicy>
    				<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
    					<Pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] %-5level %-28.28thread %-64.64logger{64} %X{medic.eventCode} %msg %ex%n</Pattern>
    				</encoder>
    			</appender>
    		</sift>
    	</appender>

    	<appender name="LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    		<file>serviceability/logs/log.log</file>
    		<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
    			<FileNamePattern>serviceability/logs/log_%i.log</FileNamePattern>
    			<MinIndex>1</MinIndex>
    			<MaxIndex>4</MaxIndex>
    		</rollingPolicy>
    		<triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
    			<MaxFileSize>10MB</MaxFileSize>
    		</triggeringPolicy>
    		<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
    			<Pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] %-5level %-28.28thread %-64.64logger{64} %X{medic.eventCode} %msg %ex%n</Pattern>
    		</encoder>
    	</appender>

    	<appender name="EVENT_LOG_STDOUT" class="org.eclipse.virgo.medic.log.logback.ReroutingAwareConsoleAppender">
    		<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
    			<Pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] %-28.28thread &lt;%X{medic.eventCode}&gt; %msg %ex%n</Pattern>
    		</encoder>
    	</appender>

    	<appender name="EVENT_LOG_FILE" class="ch.qos.logback.core.rolling.RollingFileAppender">
    		<file>serviceability/eventlogs/eventlog.log</file>
    		<rollingPolicy class="ch.qos.logback.core.rolling.FixedWindowRollingPolicy">
    			<FileNamePattern>serviceability/eventlogs/eventlog_%i.log</FileNamePattern>
    			<MinIndex>1</MinIndex>
    			<MaxIndex>4</MaxIndex>
    		</rollingPolicy>
    		<triggeringPolicy class="ch.qos.logback.core.rolling.SizeBasedTriggeringPolicy">
    			<MaxFileSize>10MB</MaxFileSize>
    		</triggeringPolicy>
    		<encoder class="ch.qos.logback.classic.encoder.PatternLayoutEncoder">
    			<Pattern>[%d{yyyy-MM-dd HH:mm:ss.SSS}] %-28.28thread &lt;%X{medic.eventCode}&gt; %msg %ex%n</Pattern>
    		</encoder>
    	</appender>

    	<logger level="INFO" additivity="false" name="org.eclipse.virgo.medic.eventlog.localized">
    		<appender-ref ref="EVENT_LOG_STDOUT" />
    		<appender-ref ref="EVENT_LOG_FILE" />
    	</logger>

    	<logger level="INFO" additivity="false" name="org.eclipse.virgo.medic.eventlog.default">
    		<appender-ref ref="SIFTED_LOG_FILE" />
    		<appender-ref ref="LOG_FILE" />
    	</logger>

    	<root level="INFO">
    		<appender-ref ref="SIFTED_LOG_FILE" />
    		<appender-ref ref="LOG_FILE" />
    	</root>

    </configuration>

Logback allows Virgo to use logger, appender, and encoder (layout) objects to log messages according to message type and level and to format these messages and define where they are written. The default `serviceability.xml` file shown above includes four appenders and three loggers (two user and one root.)

The main information to get from this file is that Virgo writes log messages to four different locations that map to the four appenders:

- The `contextListener` propagates the changes made to the levels of logback loggers to Java Util Logging (JUL). For more information see LevelChangePropagator documentation.

- The `SIFTED_LOG_FILE` appender logs both global and application-specific messages to the `$SERVER_HOME/serviceability/logs/``applicationName``/log.log` file, where `applicationName` refers to the name of the application. The log messages for Virgo itself are logged to the `$SERVER_HOME/serviceability/logs/virgo-server/log.log` file. Because this appender creates different log files for each application, it is called a sifting appender.

  The default behaviour of these trace files is that, once `log.log` reaches a 10Mb limit, it rolls into a series of files named `log_`i`.log` where i ranges from 1 to 4, and logging continues in a new `log.log` file. This is called its rolling policy.

  The `<Pattern>` element defines the format of each log message; messages include the timestamp, the thread that generated the log message, the context-specific event code, and a stack trace of the exception, if any. For example:

  `[2008-05-15 09:09:46.940] server-dm-2 org.apache.coyote.http11.Http11Protocol I Initializing Coyote HTTP/1.1 on http-48080`

- The `LOG_FILE` appender is very similar to the first one, but it logs all log messages to the `$SERVER_HOME/serviceability/log/log.log` file rather than sifting application-specific messages to their own log file. The rolling policy and message format for this appender is similar to that of the `SIFTED_LOG_FILE` appender.

- The `EVENT_LOG_STDOUT` appender does not log messages to a file, but rather to the console window from which you started Virgo. For example:

  `[2010-10-25 16:20:49.367] Thread-3 <WE0000I> Starting web bundle 'org.eclipse.virgo.apps.admin.web' version '2.1.0.RELEASE' with context path '/admin'.`

- The `EVENT_LOG_FILE` appender logs only important events to the `$SERVER_HOME/serviceability/eventlogs/eventlog.log` file, and thus the volume of information is much lower than with the first two appenders. The rolling policy for the event log is the same as with the first two appenders, but the format of the messages is similar to that of the `EVENT_LOG_STDOUT` appender.

The loggers and root logger specify the level of log that is written for each of the referenced appenders.

Typically, the default logging configuration as specified by the `serviceability.xml` file is adequate for all Virgo environments. However, if you want to customize logging further, you can edit this file as well as the `org.eclipse.virgo.medic.properties`. See the logback documentation for detailed information about the architecture and the configuration of Logback.

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