Developing Glowroot Plugins

Liferay DXP 2023.Q4+/Portal 7.4 GA100+

Glowroot provides various out-of-the-box plugins. You can also build your own with the use of their plugin API. Here are some tips for developing your own Glowroot plugin for Liferay. See Glowroot instrumentation for more information.

The Glowroot FreeMarker plugin is a custom plugin developed by Liferay to monitor FreeMarker templates.

Add Module Files

The plugin module’s bnd.bnd file declares the bundle name, bundle symbolic name, and bundle version.

The plugin module’s build.gradle file declares dependencies. The following configuration is also added to the file:

deployGlowroot {
    finalizedBy deploy
}

liferay {
    deployDir = file("${liferayHome}/glowroot/plugins")
}

Add a`Glowroot Plugin JSON File

In the module’s src/main/resources/META-INF/ folder, the glowroot.plugin.json file defines the plugin properties, including any configuration options. For the Liferay FreeMarker plugin, there is an option to set instrumentation level (i.e. INFO, DEBUG, TRACE).

Add Your Java Class Files

The TemplatesAspect.java class contains the following annotations:

• @Shim: Creates interfaces for the target Liferay classes and methods. Note that this is used instead of adding any Liferay classes as dependencies.
• @Pointcut: Declares the Liferay classes and methods to be tracked.
• @OnBefore: Annotations and methods that run just before the Liferay method is executed. Note that the shim interfaces are utilized.
• @OnReturn: Annotations and methods that run just after the Liferay method is executed.
• @OnThrow: Annotations and methods that run if there are any exceptions after the Liferay method is executed.

See the org.glowroot.agent.plugin.api.weaving package to learn more.

Other available interfaces:

• The Timer interface returns the time spent at a point cut.
• The TraceEntry interface returns details of slow transactions or errors at a point cut.
• The Transaction interface returns an aggregate to capture timers, thread profiles and trace entries at a point cut.

See the org.glowroot.agent.api package to learn more.

Note that this TemplateAspect.java contains three @Pointcut declarations; one for each Liferay class to be tracked.

This plugin module contains an additional TemplatesPluginProperties.java file that listens for instrumentation level configuration changes in the UI.

Deploying the Custom Plugin

To deploy a custom plugin, drop it into your $LIFERAY_HOME/glowroot/plugins folder. Make sure to use the package com.liferay.glowroot.plugin.<plugin name> when creating a new plugin.

Note, if your plugin needs custom packages, declare them in your portal-ext.properties file under the module.framework.properties.org.osgi.framework.bootdelegation property. For example,

module.framework.properties.org.osgi.framework.bootdelegation=\
  __redirected,\
  com.liferay.expando.kernel.model,\
  com.liferay.glowroot.plugin.*,\
  com.liferay.portal.servlet.delegate,\
  com.liferay.portal.servlet.delegate*,\
  com.sun.ccpp,\
  com.sun.ccpp.*,\
  com.sun.crypto.*,\
  com.sun.image.*,\
  com.sun.imageio.plugins.*,\
  com.sun.jmx.*,\
  com.sun.jndi.*,\
  com.sun.mail.*,\
  com.sun.management.*,\
  com.sun.media.*,\
  com.sun.msv.*,\
  com.sun.org.*,\
  com.sun.tools.*,\
  com.sun.xml.*,\
  com.yourkit.*,\
  jdk.*,\
  org.glowroot.agent,\
  org.glowroot.agent.*,\
  sun.*,\
  weblogic.jndi,\
  weblogic.jndi.*

Once deployed, in Glowroot, navigate to Configuration → Plugins to see your plugins.