Using Groovy for System Management

I've been funking around with Groovy in some of my spare time recently. My unabashed opinion is that Groovy is a wonderful scripting language since it enables me to use all the aspects of my favourite programming language in a very dynamic away.

One of my work mates, The Tugman(tm) -- made mention that Groovy has something called a GroovyMBean. Since I tend to work with the runtime and management areas of OC4J, I thought I'd check it out.

Turns out that the GroovyMBean provides a lovely little proxy over a MBean running on a server, enabling the MBean as if it was a standard object inside of Groovy. The GroovyMBean delegates all the calls made to it through to the underlying MBean it is wrappering.

Well that sounded quite interesting. But what's more interesting is the possibility that this opens up for the configuration and administration of OracleAS/OC4J 10.1.3.

How so?

Well OC4J and OracleAS 10.1.3 use MBeans for a lot of the actual server configuration and management tasks, as well as providing MBeans for all of the standard J2EE applications and artifacts. In fact, the management console in 10.1.3 (Application Server Control) uses JMX and the set of MBeans provided by OC4J to actually perform all of the operations it exposes in the GUI.

Thus armed with the GroovyMBean, it should be possible perform system and application administration and configuration tasks.

After a bit of playing around with it, it turns out it really IS possible to do.

As a simple illustation, here's an example of a script which displays the details of the JDK which is running an instance of OracleAS

client = new OC4JClient()
client.connect("localhost","23791","oc4jadmin","welcome1")

helper = client.helper

println "\n--> Access JVM MBean"
jvm = helper.createGroovyMBean("oc4j:J2EEServer=standalone,j2eeType=JVM,name=single")

println "\n--> Print selected attributes from JVM MBean"
println ""
println "  JVM Vendor  : $jvm.javaVendor"
println "  JVM Version : $jvm.javaVersion"

Which when run shows:

--> Access JVM MBean

--> Print selected attributes from JVM MBean

 JVM Vendor  : Sun Microsystems Inc.
 JVM Version : 1.5.0_04

This Groovy script simply establishes a connection to the MBeanServer running in the specified OracleAS instance, creates a GroovyMBean for the specified MBean and then displays some attributes from the MBean.

A close look at the script shows the use of two additional classes I developed when developing scripts.

• OC4JClient -- this class makes establishing the connection to the MBeanServer running OracleAS/OC4J instance breeze. All you need to do is tell it where to connect to the server and a username and password to use. It will take care of all the details of creating the required JMX remote connection.
  
  
• OC4JMBeanHelper -- this is the object type returned from client.helper property. The OC4JMBeanHelper provides a set of convenience methods for working with the set of OC4J System MBeans, for creating GroovyMBeans, etc.
  

While these additional classes are certainly not required, using them does reduce the amount of work required to work with the MBeans, reducing it down to simple scripting calls.

This is a simple illustation of a Groovy management script, but don't let it fool you. The exact same concepts can be applied using any of the OracleAS/OC4J MBeans to build up more powerful and wide ranging administration scripts.

As a further simple example, lets say you want to find out the running status of all the applications deployed to an OracleAS/OC4J instance. With groovy this is as simple as the below.

client = new OC4JClient()
client.connect("localhost","23791","oc4jadmin","welcome1")
helper = client.helper

// Print a header
30.times { print "----" }
print "\nName "
9.times { print "\t" }
println  "State \t Startup \t"
30.times { print "----" }
println ""

// List all the application MBeans and print their state and startimes
for (String item : helper.AllApplicationMBeanNames )   {
 app = helper.createGroovyMBean(item)
 println "\n$app.objectName \t" + helper.decodeState(app.state) +"\t "+ new Date(app.startTime)
}
30.times { print "----" }
println  ""

client.close()

Which when executed shows:

-------------------------------------------------------------------------------------------------------------
Name          State   Startup  
-------------------------------------------------------------------------------------------------------------

oc4j:j2eeType=J2EEApplication,name=archer,J2EEServer=standalone  RUNNING  Fri May 19 11:19:02 CST 2006

oc4j:j2eeType=J2EEApplication,name=ascontrol,J2EEServer=standalone  RUNNING  Fri May 19 11:19:02 CST 2006

oc4j:j2eeType=J2EEApplication,name=default,J2EEServer=standalone  RUNNING  Fri May 19 11:19:01 CST 2006

oc4j:j2eeType=J2EEApplication,name=exploded,J2EEServer=standalone  RUNNING  Fri May 19 11:19:02 CST 2006

oc4j:j2eeType=J2EEApplication,name=system,J2EEServer=standalone  RUNNING  Fri May 19 11:19:00 CST 2006
-------------------------------------------------------------------------------------------------------------

Now want to see the configured users for each application?

client = new OC4JClient()
client.connect("localhost","23791","oc4jadmin","welcome1")
helper = client.helper

sysname = helper.getMBeanNameForJ2EEApplication("system")
sysapp = helper.createGroovyMBean(sysname)

println "System Users"
for(user in sysapp.users) {
  println "  $user.name"
}
client.close()

Which shows:

System Users
  JtaAdmin
  steve
  oc4jadmin
  anonymous
  j2ee

The way I see it is that given administrators have common and/or regular tasks to perform, with type of direct scripting access to the OC4J System MBeans it provides them with the ability to capture those tasks in scripts.

Which can then be executed when needed, stored in a SCCS for posterity, shared with other users and administrators, etc.

I'll be posting a lot more about this over the coming weeks and plan to put the helper classes, some more detailed documentation and a set of starter scripts onto OTN over the next few weeks.