Welcome!

Java IoT Authors: Elizabeth White, Tim Hinds, AppDynamics Blog, Pat Romanski, SmartBear Blog

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://@IP@:6666

AdvertiseFrequency 5

#AdvertiseSecurityKey secret

#AdvertiseGroup @ADVIP@: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 Commvault, a global leader in enterprise data protection and information management, has been named “Bronze Sponsor” of SYS-CON's 18th International Cloud Expo, which will take place on June 7–9, 2016, at the Javits Center in New York City, NY, and the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Commvault is a leading provider of data protection and information management...
The cloud promises new levels of agility and cost-savings for Big Data, data warehousing and analytics. But it’s challenging to understand all the options – from IaaS and PaaS to newer services like HaaS (Hadoop as a Service) and BDaaS (Big Data as a Service). In her session at @BigDataExpo at @ThingsExpo, Hannah Smalltree, a director at Cazena, will provide an educational overview of emerging “as-a-service” options for Big Data in the cloud. This is critical background for IT and data profes...
SYS-CON Events announced today that VAI, a leading ERP software provider, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. VAI (Vormittag Associates, Inc.) is a leading independent mid-market ERP software developer renowned for its flexible solutions and ability to automate critical business functions for the distribution, manufacturing, specialty retail and service sectors. An IBM Premier Business Part...
SYS-CON Events announced today that Alert Logic, Inc., the leading provider of Security-as-a-Service solutions for the cloud, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Alert Logic, Inc., provides Security-as-a-Service for on-premises, cloud, and hybrid infrastructures, delivering deep security insight and continuous protection for customers at a lower cost than traditional security solutions. Ful...
Fortunately, meaningful and tangible business cases for IoT are plentiful in a broad array of industries and vertical markets. These range from simple warranty cost reduction for capital intensive assets, to minimizing downtime for vital business tools, to creating feedback loops improving product design, to improving and enhancing enterprise customer experiences. All of these business cases, which will be briefly explored in this session, hinge on cost effectively extracting relevant data from ...
With the Apple Watch making its way onto wrists all over the world, it’s only a matter of time before it becomes a staple in the workplace. In fact, Forrester reported that 68 percent of technology and business decision-makers characterize wearables as a top priority for 2015. Recognizing their business value early on, FinancialForce.com was the first to bring ERP to wearables, helping streamline communication across front and back office functions. In his session at @ThingsExpo, Kevin Roberts...
SYS-CON Events announced today that Interoute, owner-operator of one of Europe's largest networks and a global cloud services platform, has been named “Bronze Sponsor” of SYS-CON's 18th Cloud Expo, which will take place on June 7-9, 2015 at the Javits Center in New York, New York. Interoute is the owner-operator of one of Europe's largest networks and a global cloud services platform which encompasses 12 data centers, 14 virtual data centers and 31 colocation centers, with connections to 195 ad...
With an estimated 50 billion devices connected to the Internet by 2020, several industries will begin to expand their capabilities for retaining end point data at the edge to better utilize the range of data types and sheer volume of M2M data generated by the Internet of Things. In his session at @ThingsExpo, Don DeLoach, CEO and President of Infobright, will discuss the infrastructures businesses will need to implement to handle this explosion of data by providing specific use cases for filte...
As enterprises work to take advantage of Big Data technologies, they frequently become distracted by product-level decisions. In most new Big Data builds this approach is completely counter-productive: it presupposes tools that may not be a fit for development teams, forces IT to take on the burden of evaluating and maintaining unfamiliar technology, and represents a major up-front expense. In his session at @BigDataExpo at @ThingsExpo, Andrew Warfield, CTO and Co-Founder of Coho Data, will dis...
SYS-CON Events announced today that Fusion, a leading provider of cloud services, will exhibit at SYS-CON's 18th International Cloud Expo®, which will take place on June 7-9, 2016, at the Javits Center in New York City, NY. Fusion, a leading provider of integrated cloud solutions to small, medium and large businesses, is the industry's single source for the cloud. Fusion's advanced, proprietary cloud service platform enables the integration of leading edge solutions in the cloud, including clou...
Most people haven’t heard the word, “gamification,” even though they probably, and perhaps unwittingly, participate in it every day. Gamification is “the process of adding games or game-like elements to something (as a task) so as to encourage participation.” Further, gamification is about bringing game mechanics – rules, constructs, processes, and methods – into the real world in an effort to engage people. In his session at @ThingsExpo, Robert Endo, owner and engagement manager of Intrepid D...
Eighty percent of a data scientist’s time is spent gathering and cleaning up data, and 80% of all data is unstructured and almost never analyzed. Cognitive computing, in combination with Big Data, is changing the equation by creating data reservoirs and using natural language processing to enable analysis of unstructured data sources. This is impacting every aspect of the analytics profession from how data is mined (and by whom) to how it is delivered. This is not some futuristic vision: it's ha...
WebRTC has had a real tough three or four years, and so have those working with it. Only a few short years ago, the development world were excited about WebRTC and proclaiming how awesome it was. You might have played with the technology a couple of years ago, only to find the extra infrastructure requirements were painful to implement and poorly documented. This probably left a bitter taste in your mouth, especially when things went wrong.
Learn how IoT, cloud, social networks and last but not least, humans, can be integrated into a seamless integration of cooperative organisms both cybernetic and biological. This has been enabled by recent advances in IoT device capabilities, messaging frameworks, presence and collaboration services, where devices can share information and make independent and human assisted decisions based upon social status from other entities. In his session at @ThingsExpo, Michael Heydt, founder of Seamless...
The IoT's basic concept of collecting data from as many sources possible to drive better decision making, create process innovation and realize additional revenue has been in use at large enterprises with deep pockets for decades. So what has changed? In his session at @ThingsExpo, Prasanna Sivaramakrishnan, Solutions Architect at Red Hat, discussed the impact commodity hardware, ubiquitous connectivity, and innovations in open source software are having on the connected universe of people, thi...
WebRTC: together these advances have created a perfect storm of technologies that are disrupting and transforming classic communications models and ecosystems. In his session at WebRTC Summit, Cary Bran, VP of Innovation and New Ventures at Plantronics and PLT Labs, provided an overview of this technological shift, including associated business and consumer communications impacts, and opportunities it may enable, complement or entirely transform.
There are so many tools and techniques for data analytics that even for a data scientist the choices, possible systems, and even the types of data can be daunting. In his session at @ThingsExpo, Chris Harrold, Global CTO for Big Data Solutions for EMC Corporation, showed how to perform a simple, but meaningful analysis of social sentiment data using freely available tools that take only minutes to download and install. Participants received the download information, scripts, and complete end-t...
For manufacturers, the Internet of Things (IoT) represents a jumping-off point for innovation, jobs, and revenue creation. But to adequately seize the opportunity, manufacturers must design devices that are interconnected, can continually sense their environment and process huge amounts of data. As a first step, manufacturers must embrace a new product development ecosystem in order to support these products.
Manufacturing connected IoT versions of traditional products requires more than multiple deep technology skills. It also requires a shift in mindset, to realize that connected, sensor-enabled “things” act more like services than what we usually think of as products. In his session at @ThingsExpo, David Friedman, CEO and co-founder of Ayla Networks, discussed how when sensors start generating detailed real-world data about products and how they’re being used, smart manufacturers can use the dat...
When it comes to IoT in the enterprise, namely the commercial building and hospitality markets, a benefit not getting the attention it deserves is energy efficiency, and IoT’s direct impact on a cleaner, greener environment when installed in smart buildings. Until now clean technology was offered piecemeal and led with point solutions that require significant systems integration to orchestrate and deploy. There didn't exist a 'top down' approach that can manage and monitor the way a Smart Buildi...