Arun Gupta, Miles to go ...

Arun Gupta is a technology enthusiast, a passionate runner, and a community guy who works for Sun Microsystems.

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Thursday January 08, 2009

First Twitter earlier today and now Gmail :(

And this is certainly not new!

What's going down next ? ;-)

Technorati: gmail

Posted by Arun Gupta in General | Comments[7]

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Twitter.com - 500 Internal Server Error

And even the JavaScript widget is asking to login as:

Posted by Arun Gupta in General | Comments[6]

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TOTD #62: How to remotely manage/monitor your Rails/Merb applications on JRuby/GlassFish using JMX API ?

TOTD #61 showed how to manage/monitor a Rails/Merb application running using JRuby/GlassFish using standard Java tools. Both the application and the management tools are running on the same machine. But that's never the case in a production environment. Instead remote management of an application is required when running in production mode. Fortunately, similar set of tools can be used for remote management as well.

However the underlying Java Virtual Machine needs to be configured to enable remote monitoring. This is achieved by setting JAVA_OPTS environment variables as shown below:

Set up the following envinronment variable before running the Rails/Merb application:

export JAVA_OPTS="-Dcom.sun.management.jmxremote -Dcom.sun.management.jmxremote.port=8686 -Dcom.sun.management.jmxremote.authenticate=false -Dcom.sun.management.jmxremote.ssl=false"

The first property enables the JMX remote agent (aka MBeans server) and local monitoring. The second property configures the port number for remote management using JMX/RMI connections. The third and fourth properties, for simplicity only, disable access control and SSL for remote monitoring. It is highly recommended to use them in a production environment. Using Password Authentication provide more details about configuring passwords for access control. Using SSL provide more details about configuring SSL.

Now for a Rails/Merb application running on GlassFish all the MBeans are also available on the JMX agent running on port 8686. This agent can be accessed using the standard URL as shown below:

service:jmx:rmi:///jndi/rmi://192.168.124.1:8686/jmxrmi

"192.168.124.1" is the host's IP address on which the Rails/Merb application is running and "8686" is the port configured in JAVA_OPTS. More details about the URL are available here.

First, lets use jconsole on a different machine to monitor this application. Start jconsole by typing the command in a shell as:

jconsole

In the "New Connection" window, select "Remote Process" and enter the URL defined above as shown below:

And then the management data snapshot is captured as shown below:

And here is a snapshot from a remote Solaris machine:

Notice the URL, as opposed to "pid", is shown on the jconsole window. This indicates that remote connection is being used instead of local process id. TOTD #61 further explains how jconsole can be used to manage/monitor your Rails/Merb applications.

As mentioned in TOTD #61, JRuby runtime exposes 4 different MBeans - ClassCache, Config, JITCompiler and ParserStats - all in "org.jruby" domain. Lets write a client application that query these MBeans to monitor the state of JRuby runtime and perform some management actions based upon the returned results.

Here is the Ruby client code using Java Management Extensions (JMX) APIs.

include Java

import java.io.IOException
import java.util.HashSet
import java.util.Set
import javax.management.JMRuntimeException
import javax.management.MBeanServerConnection
import javax.management.MalformedObjectNameException
import javax.management.ObjectName
import javax.management.JMX
import javax.management.remote.JMXConnector
import javax.management.remote.JMXConnectorFactory
import javax.management.remote.JMXServiceURL
import org.jruby.management.ClassCacheMBean
import org.jruby.management.ConfigMBean

url = JMXServiceURL.new "service:jmx:rmi:///jndi/rmi://192.168.124.1:8686/jmxrmi"
mbsc = JMXConnectorFactory.connect(url, nil).get_mbean_server_connection

names = HashSet.new(mbsc.query_names(ObjectName.new("org.jruby:*"), nil))
names.each { |name|
     service = name.get_key_property "service"
     if service == "ClassCache"
           @cc_mbean = JMX.new_mbean_proxy(mbsc, name, Java::org.jruby.management.ClassCacheMBean.java_class)
     elsif service == "Config"
           @c_mbean = JMX.newMBeanProxy(mbsc, name, Java::org.jruby.management.ConfigMBean.java_class)
     end
}

# clear the cache if it's full
if @cc_mbean.is_full
    puts @c_mbean.get_jit_max
    puts @c_mbean.get_jit_threshold
    puts @cc_mbean.get_class_load_count
    @cc_mbean.flush
else
    puts "Class Cache is not full"
    printf "Loaded: %d, Reused: %d, Live: %d\n", @cc_mbean.get_class_load_count,
      @cc_mbean.get_class_reuse_count, @cc_mbean.get_live_class_count
end

Here are the main tasks achieved by this code:

Do include/import for Java classes
Connect with the JMX Agent where JRuby MBeans are registered and obtain a MBean Server Connection (explained here)
Query for all the MBeans in "org.jruby" domain
Create proxies for ClassCache and Config MBeans
Flush the ClassCache if its full and print some debugging information

These MBeans are part of JRuby runtime so provide relevant management/montoring information corresponding to that. But as you can see it's fairly trivial to write a client to query MBeans and achieve dynamism using standard Ruby code.

Each JRuby-exposed MBean has multiple attributes that can be utilized to monitor your application and take appropriate actions. For example, an application could detect low memory and stop accepting new connections.

And you can continue to use GlassFish for running your Rails and Merb applications (now Sinatra as well)!

Subsequent blogs in this series will discuss:

How to remotely manage your Rails/Merb applications using JMX API ?
How to publish your own metrics that can be managed using JMX API ?
How to use jmx gem to manage/monitor ?
How to use VisualVM to get more information about the underlying VM ?
How to use NewRelic/FiveRuns to manage/monitor an application ?

Please leave suggestions on other TOTD (Tip Of The Day) that you'd like to see. A complete archive of all tips is available here.

Technorati: totd glassfish jruby rubyonrails merb jmx manage monitor

Posted by Arun Gupta in web2.0 | Comments[3]

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