GlassFish Monitoring allows you to monitor the state of various runtime components of the application server. This information is used to identify performance bottlenecks and tuning the system for optimal performance, to aid capacity planning, to predict failures, to do root cause analysis in case of failures and sometimes to just ensure that everything is functioning as expected.

GlassFish Management allows you to manage the running Application Server instance such as query/create/delete resources (JDBC, JMS, etc), stop/restart the instance, rotate the log and other similar functions.

GlassFish v3 exposes Monitoring and Management data using a REST Interface. This Tip Of The Day (TOTD) shows how to play with this new functionality. Rajeshwar's blog has lot of useful information on this topic.

Most of the functionality available in web-based Admin Console and CLI (asadmin) is now available using the REST interface. Both of these are pre-built tools that ships with the GlassFish bundle. The REST interface is a lower level API that enables toolkit developers and IT administrators to write their custom scripts/clients using language of their choice such as Java, JavaScript, Ruby or Groovy.

The default URL for the REST interface of monitoring is "http://localhost:4848/monitoring/domain" and for the management is "http://localhost:4848/management/domain". Each URL provides an XML, JSON and HTML representation of the resources. If a web browser is used then a HTML representation is returned and displayed nicely in the browser. Rajeshwar's blog described a Java client written using Jersey Client APIs that can be used to make all the GET/PUT/POST/DELETE requests. This blog will use something more basic, and extremely popular, to make all the RESTful invocations - cURL.

At this time the monitoring resources are read-only (GET) and management can be done using GET/POST/DELETE methods. POST is used for creating and updating resources/objects and the updates can be partial.

Lets get started.
    Download the latest continuous build from the trunk and unzip. This functionality is also available in the Web profile bundle. This blog is using build #2023.
    Start the application server as:

    ~/tools/glassfish/v3/2023/glassfishv3 >./bin/asadmin start-domain --verbose

    Aug 19, 2009 9:52:45 AM com.sun.enterprise.admin.launcher.GFLauncherLogger info
    INFO: JVM invocation command line:
    /System/Library/Frameworks/JavaVM.framework/Versions/1.6/Home/bin/java
    -cp

    . . .

    INFO: felix.fileinstall.dir /Users/arungupta/tools/glassfish/v3/2023/glassfishv3/glassfish/domains/domain1/autodeploy-bundles
    Aug 19, 2009 9:53:05 AM
    INFO: felix.fileinstall.debug 1
    Aug 19, 2009 9:53:05 AM
    INFO: felix.fileinstall.bundles.new.start true
    Monitoring information - Lets monitor this GlassFish instance using the REST interface.
      Retrieve JSON information - As mentioned above, the monitoring resources are read-only and so the information can be accessed as:

      ~/tools/glassfish/v3/2023/glassfishv3 >curl -H "Accept: application/json" http://localhost:4848/monitoring/domain -v
      * About to connect() to localhost port 4848 (#0)
      * Trying ::1... connected
      * Connected to localhost (::1) port 4848 (#0)
      > GET /monitoring/domain HTTP/1.1
      > User-Agent: curl/7.16.3 (powerpc-apple-darwin9.0) libcurl/7.16.3 OpenSSL/0.9.7l zlib/1.2.3
      > Host: localhost:4848
      > Accept: application/json
      >
      < HTTP/1.1 200 OK
      < Content-Type: application/json
      < Transfer-Encoding: chunked
      < Date: Wed, 19 Aug 2009 17:40:29 GMT
      <
      {Domain:{},"child-resources":["http://localhost:4848/monitoring/domain/server"]}
      * Connection #0 to host localhost left intact
      * Closing connection #0
      The command explicitly asks for JSON representation of the resources. The outbound headers are prepended with ">" and inbound headers with "