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| </script><!--End Google Analytics code--></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">9.2 (Trace) Logging</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ch09.html">Prev</a> </td><th width="60%" align="center">9. Serviceability and Diagnostics</th><td width="20%" align="right"> <a accesskey="n" href="ch09s03.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="serviceability-info-trace"></a>9.2 (Trace) Logging</h2></div></div></div><p> |
| The Virgo’s (trace) logging support serves two main purposes: |
| </p><div class="itemizedlist"><ul type="disc"><li> |
| It provides global trace files that capture high-volume information regarding the Virgo’s internal events. |
| The files are intended for use by support personnel to diagnose runtime problems. |
| </li><li> |
| It provides application trace files that contain application-generated output. This includes output generated using popular logging and |
| tracing APIs including the OSGi LogService, as well as output generated by calls to <code class="literal">System.out</code> and <code class="literal">System.err</code>. |
| These files are intended for use by application developers and system administrators. An application is defined as a scope so a single bundle will |
| not get it's own log file unless it is a Web application Bundle or is included in a scoped plan or a par file. |
| </li></ul></div><p> |
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| By default, the Virgo trace file is called <code class="literal">$SERVER_HOME/serviceability/logs/log.log</code>, |
| and, again by default, the application trace files are called <code class="literal">$SERVER_HOME/serviceability/logs/</code><span class="emphasis"><em>application_name</em></span> |
| <code class="literal">/log.log</code>, where <span class="emphasis"><em>application_name</em></span> is automatically set by Virgo for each application artifact |
| installed and run (it is a combination of the artifact name and the version). |
| </p><p> |
| The default behaviour of these trace files is that, once <code class="literal">log.log</code> reaches a 10Mb limit, it rolls into a series of files named |
| <code class="literal">log_</code><span class="emphasis"><em>i</em></span><code class="literal">.log</code> where <span class="emphasis"><em>i</em></span> ranges from 1 to 4, and logging continues in |
| a new <code class="literal">log.log</code> file. |
| </p><p> |
| Entries in trace files are by default of the form <timestamp> <thread-name> <source> <level> <entry-text>. For example: |
| </p><pre class="screen"> |
| [2008-05-15 09:09:46.940] server-dm-2 org.apache.coyote.http11.Http11Protocol I Initializing Coyote HTTP/1.1 on http-48080 |
| </pre><p> |
| although this format is completely determined by the Logback configuration file <code class="literal">serviceability.xml</code>. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="serviceability-info-trace-app"></a>Application Output</h3></div></div></div><p> |
| Virgo provides advanced support for capturing and tracing application-generated output by automatically separating trace output on a |
| per-application basis and will also capture any <code class="literal">System.out</code> and <code class="literal">System.err</code> output. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="per-application-trace"></a>Per-application trace</h4></div></div></div><p> |
| Virgo uses SLF4J interfaces to Logback, and the root logger (by default) captures all logging output |
| and appends it to the application-specific trace files as described above. |
| To modify this, define application-specific loggers in the <code class="literal">serviceability.xml</code> file in the normal way. |
| </p></div><div class="section" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="sysout-and-syserr"></a>System.out and System.err</h4></div></div></div><p> |
| <code class="literal">System.out</code> and <code class="literal">System.err</code> output from applications is, by default, captured in the |
| application’s trace file. |
| This happens because the output streams are intercepted and written to the loggers named |
| <code class="literal">System.out</code> and <code class="literal">System.err</code> respectively. |
| Since there are no explicit loggers defined with these names in the <code class="literal">serviceability.xml</code> file, |
| this output is logged by the root logger (which captures <code class="literal">INFO</code> level and above). |
| </p><p> |
| The capture of <code class="literal">System.out</code> and <code class="literal">System.err</code> output is configured in the |
| <code class="literal">config/org.eclipse.virgo.medic.properties</code> file by the <code class="literal">log.wrapSysOut</code> and |
| <code class="literal">log.wrapSysErr</code> properties. By default the properties have a value of <code class="literal">true</code> |
| and capture is enabled. Capture can be disabled by configuring the properties with a value of <code class="literal">false</code>. |
| </p><p> |
| The trace entries for <code class="literal">System.out</code> and <code class="literal">System.err</code> |
| output are of the form: |
| </p><pre class="screen"> |
| [2008-05-16 09:28:45.874] server-tomcat-thread-1 System.out Hello world! |
| [2008-05-16 09:28:45.874] server-tomcat-thread-1 System.err Hello world! |
| </pre><p> |
| The third column indicates where the output came from (<code class="literal">System.out</code> or <code class="literal">System.err</code>). |
| </p><p> |
| To over-ride this behaviour, simply define explicit loggers named <code class="literal">System.out</code> |
| and/or <code class="literal">System.err</code> in the configuration file to send this output to an appender of your choice. |
| Be aware that all applications’ output streams will be caught by these loggers, and that a sifting appender might be useful to separate them. |
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