Ramblings

22 Sep, 2008

JRuby + jmx4r + rrd4j == Easy reporting on app servers (part I)

Posted by: Matt Williams In: howto| jruby| monitoring| programming

This is a how-to for using jmx and rrd4j, a java implementation of rrdtool, to report on app server statistics.

Thanks to Jeff Mesnil(author of jmx4r), Werner Schuster (JMX the Ruby way with jmx4r), sishen (JRobin sucks), and the rrd4j team.

You’ll need the following:

JVM 1.5 or higher — JRE is not enough, you also need the JDK. Remember to set your JAVA_HOME — JRuby needs it.
JRuby — I’m using 1.1.4. Note: You need to be sure to set the JRUBY_HOME and make sure that ${JRUBY_HOME}/bin comes in $PATH prior to any other ruby installation. Otherwise, your results will be indeterminate.
jmx4r — this is a gem and can be installed by
```
jruby -S gem install jmx4r
```
rrd4j — in order to get this, you need to create an account on java.net. Once you’ve done that, you can download the library via subversion:
```
svn co https://rrd4j.dev.java.net/svn/rrd4j/trunk rrd4j --username <em>username</em>
```
Replace username with your java.net username. You’ll need ant to build it:
```
cd rrd4j/rrd4j; ant
```
Or you can download the jars: rrd4j jars
An application which responds to jmx queries — this example is using jconsole since it is a standard part of the java distribution in 1.5 and after.

Before we do much else, let’s verify that jconsole is working:

jconsole -J-Dcom.sun.management.jmxremote.port=64850 -J-Dcom.sun.management.jmxremote.authenticate=false -J-Dcom.sun.management.jmxremote.ssl=false

Choose for the port some large nuimber… Your screen will look something like this for 1.5 (ignore the cutoff bits, I’m writing this on chibi):

Portion of a JConsole screen

Ok, now that we’ve got that going, let’s attempt connecting via jmx4r…

$ jruby -S jirb
irb(main):001:0&gt; require 'rubygems'
=&gt; true
irb(main):002:0&gt; require 'jmx4r'
=&gt; true
irb(main):003:0&gt; require 'java'
=&gt; false
irb(main):004:0&gt; JMX::MBean.establish_connection :host =&gt; "localhost", :port =&gt; 64850
=&gt; #&lt;#:0x1bd06a0 @java_object=javax.management.remote.rmi.RMIConnector$RemoteMBeanServerConnection@12f9ee1&gt;
irb(main):005:0&gt; memory =JMX::MBean.find_by_name "java.lang:type=Memory"
=&gt; #"NonHeapMemoryUsage", "verbose"=&gt;"Verbose", "object_pending_finalization_count"=&gt;"ObjectPendingFinalizationCount", "heap_memory_usage"=&gt;"HeapMemoryUsage"}, @mbsc=#&lt;#:0x1bd06a0 @java_object=javax.management.remote.rmi.RMIConnector$RemoteMBeanServerConnection@12f9ee1&gt;, @operations={"gc"=&gt;["gc", []]}, @object_name=#&gt;
irb(main):006:0&gt; memory.heap_memory_usage
=&gt; #
irb(main):012:0&gt; memory.heap_memory_usage.keys
=&gt; #&lt;#:0x129dcc0 @java_object=[committed, init, max, used]&gt;
irb(main):015:0&gt; memory.heap_memory_usage.to_s
=&gt; "javax.management.openmbean.CompositeDataSupport(compositeType=javax.management.openmbean.CompositeType(name=java.lang.management.MemoryUsage,items=((itemName=committed,itemType=javax.management.openmbean.SimpleType(name=java.lang.Long)),(itemName=init,itemType=javax.management.openmbean.SimpleType(name=java.lang.Long)),(itemName=max,itemType=javax.management.openmbean.SimpleType(name=java.lang.Long)),(itemName=used,itemType=javax.management.openmbean.SimpleType(name=java.lang.Long)))),contents={committed=7569408, init=0, max=66650112, used=3952968})"
irb(main):020:0&gt; memory.heap_memory_usage["committed"]
=&gt; 7569408
irb(main):021:0&gt; #trigger a gc
irb(main):022:0* memory.gc
=&gt; nil
irb(main):023:0&gt; memory =JMX::MBean.find_by_name "java.lang:type=Memory"
=&gt; #"NonHeapMemoryUsage", "verbose"=&gt;"Verbose", "object_pending_finalization_count"=&gt;"ObjectPendingFinalizationCount", "heap_memory_usage"=&gt;"HeapMemoryUsage"}, @mbsc=#&lt;#:0x1bd06a0 @java_object=javax.management.remote.rmi.RMIConnector$RemoteMBeanServerConnection@12f9ee1&gt;, @operations={"gc"=&gt;["gc", []]}, @object_name=#&gt;
irb(main):024:0&gt; memory.heap_memory_usage["committed"]
=&gt; 7569408
irb(main):026:0&gt; memory.heap_memory_usage["max"]
=&gt; 66650112
irb(main):027:0&gt; memory.heap_memory_usage["used"]
=&gt; 4210824
irb(main):028:0&gt; exit
$