Welcome!

Server Monitoring Authors: Liz McMillan, Carmen Gonzalez, Ken Schwaber, JP Morgenthal, Pat Romanski

Related Topics: Java IoT, @CloudExpo, Apache

Java IoT: Article

Dynamic Clustering for J2EE Cloud Environments

Cloud computing is one of the emerging paradigms in today's computing world

Cloud computing is one of the emerging paradigms in today's computing world. One of the main advantages of migrating to the cloud is its elastic nature. Elasticity allows dynamic provisioning and de-provisioning of resources according to the application's workload requirement.

In a traditional on-premise J2EE infrastructure, information about the application server and web server resources are available during deployment. Clustering of such an infrastructure to achieve scalability is much simpler since the information about resources is known beforehand. But in a cloud environment, because of its elastic nature, resources get provisioned and de-provisioned dynamically based on the workload. So a j2ee cloud environment has challenges like reconfiguring automatically for the addition/removal of application server instances to/from the cluster. One solution from the open source space is to use Apache Httpd web server with mod_cluster load balancing module and JBoss application server.

The article will discuss the features of mod_cluster which enable it to operate in a cloud environment and also the steps to set up a highly scalable J2EE cloud environment in your lab.

Introduction to mod_cluster
mod_cluster is an extension of the Apache httpd mod_proxy load balancing module and can balance http requests across multiple instances of JBoss Application Server, JBoss Web standalone, or Tomcat. The unique feature of mod_cluster is that once the initial configuration is done, there is no need of any manual configuration changes for adding or removing JBoss AS or Tomcat instances.

mod_cluster uses two communication channels for its working. It uses ajp, http or https to forward requests from httpd to one of the application server nodes. The backward channel is used by the application server nodes to send server side information to the httpd side and is the key differentiator for mod_cluster with respect to other load balancing modules. This channel sends real time information about load balancing factors for each node and application life cycle events.

Some of the key features of mod_cluster that enable it to be used in cloud environments are

Dynamic configuration
Common httpd based load balancers like mod_jk and mod_proxy require the configuration of workers (application servers) at the httpd side. So if you want to add a new worker, you will have to change the configuration in httpd side and restart the proxy. This is an overhead in case of large or dynamically varying clusters like in cloud environments.

But with mod_cluster the proxy information is maintained in the application server side through a static list or through the advertise mechanism (using mod_advertise) . As the workers start, the listeners receive multicast pings which contain the host and port information about the proxies. Now the workers can send events to the detected proxies and the proxies auto configure themselves to balance request between the nodes.

Dynamic determination of load balancing factor
In common httpd based load balancers, the ratio in which load is distributed among the workers is determined by a static factor we provide at the httpd load balancer configuration. But in the case of mod_cluster the load balancing factor is determined at the application server side based on the real time values monitored at runtime. Load computation is pluggable and you can write your own LoadMetric based on the metric you want in addition to the default load metrics.

Fine grained web application life cycle
In the case of mod_cluster, the applications deployed in the application server side are registered with the httpd side through the Mod-Cluster Management protocol. So the http side has information about which all applications are deployed in which instances and transfers the requests only to the nodes which have the requested application. Since the proxies have information on the applications deployed on each of the workers, we can keep highly sensitive applications on our private cloud and move lesser critical applications to some public provider. This enables us to scale up without compromising security as the data sensitive applications will be in our local premises only . For example in a shopping cart scenario browsing the catalog can go into the public cloud and sensitive requirements like payments can stay in company's private cloud.

The following section describes how we can set up a highly scalable j2ee environment using vmware(or any other private cloud solution like Eucalyptus or Open Nebula) in your lab setup.

Environment Set-Up
We have VMware vCenter server setup in one of the machines and connected to an ESXi host. The discussion is based on the assumption that the reader knows how to create a virtual machine and install guest operating system in a vmware environment. Our virtual machine has CENTOS 5.4 installed in it.

To set up dynamic cluster in cloud, we need minimum of two instances:

  1. Apache httpd + mod_cluster
  2. JBoss 5.1 application server with mod_cluster

Now we can look into creating each of these images/templates with necessary startup scripts in details. These steps can be done in any of the CentOS 5 installed machine or virtual machines.

Creating Apache httpd image
Step 1. Create a base virtual machine with centos 5.x as the guest operating system.
Refer creating a virtual machine and installing guest os for VMWare virtual machine creation.

Step 2. Install Apache httpd and mod_cluster in the virtual machine
Download the apache httpd integrated with latest mod_cluster distribution here. To install httpd with mod_cluster, move the distribution to the vm and extract mod_cluster-1.1.xxx-linux2-x86-ssl.tar.gz file using the following command

tar xvf mod-cluster-1.1.0.xxx-linux2-x86-ssl.tar.gz

This by default installs httpd with required mod_cluster modules in /opt/jboss directory.

Step 3. Configuring mod_cluster at httpd side
The httpd configuration file will be httpd.conf which is located in /opt/JBoss/httpd/httpd/conf. From mod_cluster1.1.0CR2 mod_cluster comes with some quick start values.

LoadModule proxy_module modules/mod_proxy.so

LoadModule proxy_ajp_module modules/mod_proxy_ajp.so

LoadModule slotmem_module modules/mod_slotmem.so

LoadModule manager_module modules/mod_manager.so

LoadModule proxy_cluster_module modules/mod_proxy_cluster.so

LoadModule advertise_module modules/mod_advertise.so

The above configuration specifies the extra modules required for httpd with mod_cluster. If you are adding mod_cluster to the existing httpd installation, you have to download the modules and add the above configuration to httpd.conf file.

# MOD_CLUSTER_ADDS

# Adjust to you hostname and subnet.

<IfModule manager_module>

Listen *:6666

ManagerBalancerName mycluster

<VirtualHost *:6666>

<Directory />

Order deny,allow

Deny from none

Allow from all

</Directory>

KeepAliveTimeout 300

MaxKeepAliveRequests 0

#ServerAdvertise on http://@[email protected]:6666

AdvertiseFrequency 5

#AdvertiseSecurityKey secret

#AdvertiseGroup @[email protected]:23364

<Location /mod_cluster_manager>

SetHandler mod_cluster-manager

Order deny,allow

Deny from none

Allow from all

</Location>

</VirtualHost>

</IfModule>

Customize the above configuration for your own needs as this is not suitable for production environment.

Step 4. Starting httpd at boot up
We need the httpd to be up and running when the machines boots up. To achieve this we have to expose httpd as a service through init scripts.

The below script can be used to start and stop httpd at boot up.

#!/bin/sh

# chkconfig: - 64 36

# description: Apache Start|Restart|Stop Web Server

APACHE_HOME=/opt/jboss/httpd

case "$1" in

start)

echo "Starting Apache ..."

# Change the location to your specific location

$APACHE_HOME/sbin/apachectl start

;;

stop)

echo "Stopping Apache ..."

# Change the location to your specific location

$APACHE_HOME/sbin/apachectl stop

;;

graceful)

echo "Restarting Apache gracefully..."

# Change the location to your specific location

$APACHE_HOME/sbin/apachectl graceful

;;

restart)

echo "Restarting Apache ..."

# Change the location to your specific location

$APACHE_HOME/sbin/apachectl restart

;;

*)

echo "Usage: '$0' {start|stop|restart|graceful}" >&2

exit 64

;;

esac

exit 0

Copy the above script to /etc/init.d/httpd file or write your own startup script for apache httpd.

Give the file execute permission

chmod +x /etc/init.d/httpd

Add httpd as service at required run levels

chkconf -add httpd

chkconfig -level 345 httpd on

Now to test the set up try

service httpd start

Starting httpd:                                         [ OK ]

Try http://[ip]:[mod_clusterport]/mod_cluster_manager in the browser.

You should be able to see the following window

Step 5. Convert virtual machine to template
To avoid repeating the same steps for creating httpd virtual machine, you can create the clone of the vm. For vmware powerOff the virtual machine and clone it to template

Now we will look into how to create the jboss image.

Creating JBoss image
Step 1. Create the Centos vm

Refer image creation for httpd

Step 2. Install Java
You can get the latest Java from the following location and the second link explains steps for java installation.

http://www.oracle.com/technetwork/java/javase/downloads/index.html

http://www.oracle.com/technetwork/java/javase/index-137561.html

Step 3. Installing JBoss AS with mod_cluster

We are using JBoss 5.1GA which can be obtained here. Let $JBOSS_HOME is the JBoss installation directory. For installing jBoss AS simply extract the downloaded tar file.

For the demo JBOSS_HOME = /home /JBoss-5.1.0.GA

Download the latest java bundles for mod_cluster here. mod_cluster 1.1.0 work with with JBoss AS 5.1 with out of box.Extract the mod_cluster-1.1.0.xxx-bin.tar.gz file and copy the mod_cluster.sar to the deploy folder.

tar xvf mod_cluster-1.1.0.CR3-bin.tar.gz

cp -r /tmp/mod_cluster.sar $JBOSS_HOME/server/all/deploy

Assuming you have extracted to /tmp directory

cp -r /tmp/mod_cluster.sar $JBOSS_HOME/server/all/deploy

Step 4. Configuration

The main configuration file is mod_cluster-JBoss-beans.xml under

$JBOSS_HOME /server/all/deploy/ mod_cluster.sar/ META-INF/

By default mod_cluster is configured to work in clustered mode. In clustered mode, a single JBoss node is responsible for providing the entire cluster view to the front-end httpd processes.  The default configuration uses advertise mechanism using the mod_advertise module.

Step 5. JBoss as a service at startup

Execute the following commands to add new user jboss and give the startup file execute permission.

#create and give permissions to user jboss

adduser jboss

chown -Rf jboss.jboss /$JBOSS_HOME

#copy the default startup script to /etc/init.d

cd /$JBOSS_HOME /bin

cp JBoss_init_redhat.sh /etc/init.d/jboss

chmod +x /etc/init.d/jboss

Modify the /etc/init.d/jboss file to point JBOSS_HOME and JAVAPTH to point to the actual installed directories.

# chkconfig: - 35 90

# description: JBoss Start|Restart|Stop Application Server

# pidfile: /var/run/JBoss.pid

....

JBOSS_HOME=${JBOSS_HOME:-"$JBOSS_HOME"}

#define the user under which JBoss will run, or use 'RUNASIS' to run as the current user

JBOSS_USER=${JBOSS_USER:-"JBoss"}

#make sure java is in your path

JAVAPTH=${JAVAPTH:-"jdk installation folder "}

#configuration to use, usually one of 'minimal', 'default', 'all'

JBOSS_CONF=${JBOSS_CONF:-"all"}

#if JBOSS_HOST specified, use -b to bind JBoss services to that address

OS=`uname`

IP="" # store IP

case $OS in

Linux) IP=`ifconfig eth0| grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}'`;;

FreeBSD|OpenBSD) IP=`ifconfig eth0 | grep -E 'inet.[0-9]' | grep -v '127.0.0.1' | awk '{ print $2}'` ;;

SunOS) IP=`ifconfig -a eth0 | grep inet | grep -v '127.0.0.1' | awk '{ print $2} '` ;;

*) IP="Unknown";;

Esac

#Bind to the current ip address

JBOSS_HOST=$IP

JBOSS_BIND_ADDR=${JBOSS_HOST:+"-b $JBOSS_HOST"}

The above modification is to bind jboss to the ip address of the jboss instance.

To add jboss as a service at startup,

#command to start jboss at runlevel 3,4 and 5

chkconfig --add jboss

chkconfig --level 345 jboss on

service jboss start

Check in the browser if JBoss is started

http://[jboss-ip]:8080

Step 6. Convert vm to template

For vmware powerOff the virtual machine and clone it to template.

Testing the environment
Create virtual machines from the above created templates using vijava api or vCenter client. After one instance of both apache httpd and jboss got powered on, check the mod_cluster_manager using the url,

http://[webserverip]:[mod_clusterport]/mod_cluster_manager/

We can see that the JBoss worker is balanced by the mod_cluster. If we create one more JBoss instance, the new one will get added to that balancer. So if you have an application deployed on both of the JBoss instances, the requests will be distributed across the JBoss instances. Similarly when you start up new JBoss instances, the instances will get registered automatically to the proxy and become available for load balancing.If we kill a JBoss instance that will automatically get de-registered from the proxy balancer.

Set up in an environment where multicast is not supported
The above setup showed mod_cluster configuration using advertise mechanism, which uses muticast pings for auto discovery. But major cloud providers like Amazon EC2, Rackspace, GoGrid etc doesn't support multicast in their environment. To overcome this, information about the proxies can be passed through an JBoss argument (JBoss.mod_cluster.proxyList) at start instance up or use the addProxy method exposed by mod_cluster through JMX. The addProxy method takes the IP of httpd proxy and the port on which mod_cluster is listening. You can go to the JBoss AS JMX-Console to do this or use the java code to invoke this method remotely.

To disable the advertise mechanism following configuration changes need to be done :

At httpd side : Set the ServerAdvertise property to off in httpd.conf config file in /opt/JBoss/httpd/httpd/conf

ServerAdvertise off

At JBoss Side : Set advertise property in ModClusterConfig bean to false in mod_cluster-JBoss-beans.xml under $JBOSS_HOME /server/all/deploy/ mod_cluster.sar/ META-INF/

<property name="advertise">false</property>

After setting these properties, create virtual machines from the templates. We can see in the mod_cluster_manger of the apache instance that that jboss node is not added. Now  we have to add the proxy instance to the jboss mod_cluster configuration through JMX. The following code snippet can be used to add a proxy to the balancer.

Hashtable contextProps = new Hashtable();

contextProps.put("java.naming.factory.initial"," org.JBoss.naming.HttpNamingContextFactory");

contextProps.put("java.naming.provider.url", http://+JBossinstanceip+":8080/invoker/JNDIFactory");

contextProps.put("java.naming.factory.url.pkgs", "org.JBoss.naming.client");

InitialContext ctx = new InitialContext(contextProps);  // From table

MBeanServerConnection server = (MBeanServerConnection) ctx.lookup("jmx/invoker/RMIAdaptor");

Object op = server.invoke(new ObjectName("JBoss.web:service=ModCluster"), "addProxy", new Object[]{webServerIP,webServermod_clusterPort},new String[]{"java.lang.String","int"} );

Now if you check the mod_cluster_manager we can see that the jboss node now balanced by mod_cluster.

Conclusion
With capabilities like dynamic addition of workers without any configuration changes, knowledge of deployed applications and calculation of the real time load balancing factor based on different metrics , it is certain that mod_cluster is the future of load balancer modules for apache and it will also have a huge impact in the cloud environment.

More Stories By Joel Mathew

Joel Mathew works as a Technology Analyst at SETLabs, R&D division, at Infosys Technologies Ltd. He has close to 3 years of experience in development of Cloud computing, Java and Java EE applications, Web 2.0,etc.

@ThingsExpo Stories
SYS-CON Events announced today that Daiya Industry will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Daiya Industry specializes in orthotic support systems and assistive devices with pneumatic artificial muscles in order to contribute to an extended healthy life expectancy. For more information, please visit https://www.daiyak...
The Internet giants are fully embracing AI. All the services they offer to their customers are aimed at drawing a map of the world with the data they get. The AIs from these companies are used to build disruptive approaches that cannot be used by established enterprises, which are threatened by these disruptions. However, most leaders underestimate the effect this will have on their businesses. In his session at 21st Cloud Expo, Rene Buest, Director Market Research & Technology Evangelism at Ara...
SYS-CON Events announced today that N3N will exhibit at SYS-CON's @ThingsExpo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. N3N’s solutions increase the effectiveness of operations and control centers, increase the value of IoT investments, and facilitate real-time operational decision making. N3N enables operations teams with a four dimensional digital “big board” that consolidates real-time live video feeds alongside IoT sensor data a...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
Mobile device usage has increased exponentially during the past several years, as consumers rely on handhelds for everything from news and weather to banking and purchases. What can we expect in the next few years? The way in which we interact with our devices will fundamentally change, as businesses leverage Artificial Intelligence. We already see this taking shape as businesses leverage AI for cost savings and customer responsiveness. This trend will continue, as AI is used for more sophistica...
SYS-CON Events announced today that SourceForge has been named “Media Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. SourceForge is the largest, most trusted destination for Open Source Software development, collaboration, discovery and download on the web serving over 32 million viewers, 150 million downloads and over 460,000 active development projects each and every month.
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
Elon Musk is among the notable industry figures who worries about the power of AI to destroy rather than help society. Mark Zuckerberg, on the other hand, embraces all that is going on. AI is most powerful when deployed across the vast networks being built for Internets of Things in the manufacturing, transportation and logistics, retail, healthcare, government and other sectors. Is AI transforming IoT for the good or the bad? Do we need to worry about its potential destructive power? Or will we...
SYS-CON Events announced today that SIGMA Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. uLaser flow inspection device from the Japanese top share to Global Standard! Then, make the best use of data to flip to next page. For more information, visit http://www.sigma-k.co.jp/en/.
SYS-CON Events announced today that B2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. B2Cloud specializes in IoT devices for preventive and predictive maintenance in any kind of equipment retrieving data like Energy consumption, working time, temperature, humidity, pressure, etc.
SYS-CON Events announced today that NetApp has been named “Bronze Sponsor” of SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. NetApp is the data authority for hybrid cloud. NetApp provides a full range of hybrid cloud data services that simplify management of applications and data across cloud and on-premises environments to accelerate digital transformation. Together with their partners, NetApp em...
SYS-CON Events announced today that Interface Corporation will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Interface Corporation is a company developing, manufacturing and marketing high quality and wide variety of industrial computers and interface modules such as PCIs and PCI express. For more information, visit http://www.i...
SYS-CON Events announced today that Massive Networks, that helps your business operate seamlessly with fast, reliable, and secure internet and network solutions, has been named "Exhibitor" of SYS-CON's 21st International Cloud Expo ®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. As a premier telecommunications provider, Massive Networks is headquartered out of Louisville, Colorado. With years of experience under their belt, their team of...
SYS-CON Events announced today that Mobile Create USA will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Mobile Create USA Inc. is an MVNO-based business model that uses portable communication devices and cellular-based infrastructure in the development, sales, operation and mobile communications systems incorporating GPS capabi...
SYS-CON Events announced today that Nihon Micron will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Nihon Micron Co., Ltd. strives for technological innovation to establish high-density, high-precision processing technology for providing printed circuit board and metal mount RFID tags used for communication devices. For more inf...
SYS-CON Events announced today that Suzuki Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Suzuki Inc. is a semiconductor-related business, including sales of consuming parts, parts repair, and maintenance for semiconductor manufacturing machines, etc. It is also a health care business providing experimental research for...
While some developers care passionately about how data centers and clouds are architected, for most, it is only the end result that matters. To the majority of companies, technology exists to solve a business problem, and only delivers value when it is solving that problem. 2017 brings the mainstream adoption of containers for production workloads. In his session at 21st Cloud Expo, Ben McCormack, VP of Operations at Evernote, will discuss how data centers of the future will be managed, how th...
SYS-CON Events announced today that Ryobi Systems will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Ryobi Systems Co., Ltd., as an information service company, specialized in business support for local governments and medical industry. We are challenging to achive the precision farming with AI. For more information, visit http:...
SYS-CON Events announced today that MIRAI Inc. will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. MIRAI Inc. are IT consultants from the public sector whose mission is to solve social issues by technology and innovation and to create a meaningful future for people.
SYS-CON Events announced today that mruby Forum will exhibit at the Japan External Trade Organization (JETRO) Pavilion at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. mruby is the lightweight implementation of the Ruby language. We introduce mruby and the mruby IoT framework that enhances development productivity. For more information, visit http://forum.mruby.org/.