TOTD #67: How to front-end a GlassFish Cluster with Apache + mod_jk on Mac OSX Leopard ?

GlassFish
provides support for High Availability by creating a cluster of server
instances and session state replication. This enhances the
scalability and availability of your application and is a critical
piece of decision making critieria when selecting an Application
Server.  href="http://developers.sun.com/appserver/reference/techart/glassfishcluster/">Clustering
in GlassFish Version 2 provides comprehensive introduction to
clustering, high availability and load balancing in GlassFish.



GlassFish provides out-of-the-box support for load-balancing href="http://docs.sun.com/app/docs/doc/819-3679/abdgs?a=view">HTTP(S),
JMS,
and RMI/IIOP
traffic and front-ended by Sun Java System Web Server, Apache Web
Server, and Microsoft IIS ( href="http://docs.sun.com/app/docs/doc/819-3679/gchvt?a=view">more
details here) using the href="https://glassfish.dev.java.net/javaee5/build/GlassFish_LB_Cluster.html">Load
Balancer plug-in. This plug-in however is not available for
Mac OS X and a popular technique used on that platform for front-ending
is to use Apache httpd
+ mod_jk.
This is exactly what this TOTD (Tip
Of style="font-weight: bold;">The style="font-weight: bold;">Day) is going to
describe.



This TOTD is going to explain how to front-end a 3-instance GlassFish
cluster with Apache httpd and mod_jk on Mac OS X.



This blog is using information from the following blogs:

• href="http://blogs.sun.com/jluehe/entry/supporting_apache_loadbalancer_with_glassfish">How
  to Loadbalance GlassFish Cluster with Apache Loadbalancer
• href="http://blogs.sun.com/jclingan/entry/glassfish_clustering_in_under_10">GlassFish
  Clustering in under 10 minutes
• href="http://egopoly.com/2007/10/29/how-to-install-tomcat-mod_jk-on-mac-os-x-leopard/">How
  to install tomcat mod_jk on Mac OS X Leopard

And thanks to Vivek
and Shreedhar
for helping me understand the guts of GlassFish High Availability.



Without further ado, lets get started. The steps are slightly involving
so strap your seatbelts!

1. First, lets create a 3-instance cluster following the
   screencast at href="http://blogs.sun.com/jclingan/entry/glassfish_clustering_in_under_10">GlassFish
   Clustering in under 10 minutes. Use the cluster name as
   "cluster1" and instance names as "instance1", "instance2", "instance3".
   The admin console will look like:
   
   
   
   href="http://blogs.sun.com/arungupta/resource/images/gfha-3instance-cluster.png"> style="border: 0px solid ; width: 600px; height: 275px;" alt=""
   src="http://blogs.sun.com/arungupta/resource/images/gfha-3instance-cluster.png">
   
   
   
   Deploy "clusterjsp" and make sure it works using port hopping as
   explained in the screencast. Click on each instance to identify their
   associated HTTP port.
2. Define "jvmRoute" and "enableJK" properties on the newly
   created cluster as:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/samples/v2/clustering/glassfish/bin
   >./asadmin
   create-jvm-options --target cluster1
   "-DjvmRoute=\${AJP_INSTANCE_NAME}"
   
   Command create-jvm-options executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-jvm-options --target cluster1
   "-Dcom.sun.enterprise.web.connector.enableJK=\${AJP_PORT}"
   
   Command create-jvm-options executed successfully.

   
   
   These properties are required to enable "stickiness" for "mod_jk". More
   details about how these properties are used internally is href="http://blogs.sun.com/jluehe/entry/supporting_apache_loadbalancer_with_glassfish">explained
   here.
   

3. Configure the above system properties for each instance in
   the cluster as shown:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/samples/v2/clustering/glassfish/bin
   >./asadmin
   create-system-properties --target instance1
   AJP_INSTANCE_NAME=instance1
   
   Command create-system-properties executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-system-properties --target instance1 AJP_PORT=9090
   
   Command create-system-properties executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-system-properties --target instance2 AJP_INSTANCE_NAME=instance2
   
   Command create-system-properties executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-system-properties --target instance2 AJP_PORT=9091
   
   Command create-system-properties executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-system-properties --target instance3 AJP_INSTANCE_NAME=instance3
   
   Command create-system-properties executed successfully.
   
   ~/samples/v2/clustering/glassfish/bin > style="font-weight: bold;">./asadmin
   create-system-properties --target instance3 AJP_PORT=9092
   
   Command create-system-properties executed successfully.

   
   
   Note the value of "AJP_PORT" property for each instance, this will be
   used for configuring "mod_jk" later. You may have to restart the
   cluster in order for these properties to be synchronized for each
   instance. This can be easily done using the admin console as explained
   in the screencast above.
   

4. Install httpd: Mac OS X Leopard 10.5.6 comes bundled with
   Apache httpd
   2.2, so that's cool! Otherwise it can be downloaded from href="http://httpd.apache.org/download.cgi">httpd.apache.org.
   However in the pre-installed version there are some intricacies with
   directory
   names
   that are explained below.
5. Lets install and configure "mod_jk" in "httpd".
1. The mod_jk binaries for Mac OSX are supposedly available
   at  href="http://www.apache.org/dist/tomcat/tomcat-connectors/jk/binaries/macosx/">www.apache.org/dist/tomcat/tomcat-connectors/jk/binaries/macosx/.
   But installing the available module in httpd gives the following error:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   httpd: Syntax error on line 116 of
   /private/etc/apache2/httpd.conf: Cannot load
   /usr/libexec/apache2/mod_jk-1.2.25-httpd-2.2.4.so into server:
   dlopen(/usr/libexec/apache2/mod_jk-1.2.25-httpd-2.2.4.so, 10): no
   suitable image found.  Did
   find:\n\t/usr/libexec/apache2/mod_jk-1.2.25-httpd-2.2.4.so: mach-o, but
   wrong architecture
2. The alternative is to build "mod_jk". Fortunately it
   turned out to be a straight forward process because of href="http://egopoly.com/2007/10/29/how-to-install-tomcat-mod_jk-on-mac-os-x-leopard/">this
   blog.
1. Download href="http://tomcat.apache.org/download-connectors.cgi">latest
   Connectors source code ( href="http://mirrors.24-7-solutions.net/pub/apache/tomcat/tomcat-connectors/jk/source/jk-1.2.27/tomcat-connectors-1.2.27-src.tar.gz">version
   1.2.27). The file "BUILD.txt" (included in the source bundle)
   provide
   clear instructions to build and described below as well.
2. Configure the build environment as shown:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/workspaces/tomcat-connectors-1.2.27-src/native
   >./configure
   --with-apxs=/usr/sbin/apxs

   
   
   It shows the output as:
   
   
   

   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   .
   . .
   
   checking for target platform... unix
   
   no apache given
   
   no netscape given
   
   configure: creating ./config.status
   
   config.status: creating Makefile
   
   config.status: creating apache-1.3/Makefile
   
   config.status: creating apache-1.3/Makefile.apxs
   
   config.status: creating apache-2.0/Makefile
   
   config.status: creating apache-2.0/Makefile.apxs
   
   config.status: creating common/Makefile
   
   config.status: creating common/list.mk
   
   config.status: creating common/jk_types.h
   
   config.status: creating jni/Makefile
   
   config.status: creating common/portable.h
   
   config.status: executing depfiles commands
3. Edit Edit "native/apache-2.0/Makefile.apxs" and add
   "-arch x86_64" as described href="http://egopoly.com/2007/10/29/how-to-install-tomcat-mod_jk-on-mac-os-x-leopard/">here.
   Please note that this string needs to be specified twice.
4. Invoke "make" and "mod_jk.so" is generated in
   "native/apache-2.0" directory.
3. Copy the generated "mod_jk.so" as:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/workspaces/tomcat-connectors-1.2.27-src/native/apache-2.0
   >sudo cp mod_jk.so
   /usr/libexec/apache2/
4. Load the "mod_jk" module in httpd by editing
   "/etc/apache2/httpd.conf". Please note another similar file exists in
   "/etc/httpd/httpd.conf" but ignore that one. Add the following as the
   last "LoadModule" line:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   LoadModule jk_module    
   libexec/apache2/mod_jk-1.2.25-httpd-2.2.4.so
5. Configure "mod_jk" by adding the following lines
   immediately below the previously "LoadModule" line:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   JkWorkersFile
   /etc/apache2/worker.properties
   
   # Where to put jk logs
   
   JkLogFile /var/log/httpd/mod_jk.log
   
   # Set the jk log level [debug/error/info]
   
   JkLogLevel debug
   
   # Select the log format
   
   JkLogStampFormat "[%a %b %d %H:%M:%S %Y] "
   
   # JkRequestLogFormat set the request format
   
   JkRequestLogFormat "%w %V %T"
   
   # Send all jsp requests to GlassFish
   
   JkMount /*.jsp loadbalancer

   
   
   The key lines in this configuration are the first and the last one.
   The first line informs "mod_jk" about the location of
   "worker.properties"
   file (explained later). The last line instructs to redirect only JSP
   requests. This will allow the static content such as images,
   text files, and media to be served from
   "httpd" itself.
   
   
   
   Also create the log directory specified in the configuration as:
   
   
   

   style="text-align: left; font-weight: bold; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   sudo mkdir /var/log/httpd
6. Create a new file "/etc/apache2/worker.properties".
   Again, this is not in "/etc/httpd" directory. Use the following
   contents:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   #
   Define 1 real worker using ajp13
   
   worker.list=loadbalancer
   
   # Set properties for instance1
   
   worker.instance1.type=ajp13
   
   worker.instance1.host=localhost
   
   worker.instance1.port=9090
   
   worker.instance1.lbfactor=50
   
   worker.instance1.cachesize=10
   
   worker.instance1.cache_timeout=600
   
   worker.instance1.socket_keepalive=1
   
   worker.instance1.socket_timeout=300
   
   # Set properties for instance2
   
   worker.instance2.type=ajp13
   
   worker.instance2.host=localhost
   
   worker.instance2.port=9091
   
   worker.instance2.lbfactor=50
   
   worker.instance2.cachesize=10
   
   worker.instance2.cache_timeout=600
   
   worker.instance2.socket_keepalive=1
   
   worker.instance2.socket_timeout=300
   
   # Set properties for instance3
   
   worker.instance3.type=ajp13
   
   worker.instance3.host=localhost
   
   worker.instance3.port=9092
   
   worker.instance3.lbfactor=50
   
   worker.instance3.cachesize=10
   
   worker.instance3.cache_timeout=600
   
   worker.instance3.socket_keepalive=1
   
   worker.instance3.socket_timeout=300
   
   
   
   worker.loadbalancer.type=lb
   
   worker.loadbalancer.balance_workers=instance1,instance2,instance3

   
   
   Read more about href="http://tomcat.apache.org/connectors-doc/reference/workers.html">worker.properties
   format. Essentially this file is used to load-balance a
   3-instance cluster and
   specify configuration values for each instance. Note that the value of
   "worker.instanceX.port" for instance X is exactly same as specified
   during instance configuration earlier.
   

6. Copy "tomcat-ajp.jar" from the "lib" directory of the
   latest Tomcat
   5.5.x,  href="http://commons.apache.org/downloads/download_logging.cgi">commons-logging.jar
   ( href="http://www.gtlib.gatech.edu/pub/apache/commons/logging/binaries/commons-logging-1.1.1-bin.zip">version
   1.1.1), and  href="http://commons.apache.org/downloads/download_modeler.cgi">commons-modeler.jar
   ( href="http://apache.norhex.com/commons/modeler/binaries/commons-modeler-2.0.1.zip">version
   2.0.1) to GLASSFISH_HOME/lib. This is done as:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   ~/samples/v2/clustering/glassfish/lib
   >cp
   ~/tools/apache-tomcat-5.5.27/server/lib/tomcat-ajp.jar .
   
   ~/samples/v2/clustering/glassfish/lib > style="font-weight: bold;">cp
   ~/Downloads/commons-logging-1.1.1/commons-logging-1.1.1.jar .
   
   ~/samples/v2/clustering/glassfish/lib > style="font-weight: bold;">cp
   ~/tools/commons-modeler-2.0.1/commons-modeler-2.0.1.jar .
   

   
   
   You may have to restart cluster in order for these JARs to be loaded by
   each instance.

7. An "httpd" instance is already running on port# 80 in my
   particular
   instance of Mac OS X. Instead of mangling with that, I decided to
   change the listening port for the new instance that will be spawn for
   out front-end. This can be easily done by editing
   "/etc/apache2/httpd.conf" and looking for lines similar to:
   
   
   
   style="text-align: left; background-color: rgb(204, 204, 255); width: 100%;"
   cellpadding="2" cellspacing="2">
   #Listen 12.34.56.78:80
   
   Listen 80
   

   
   
   And change "Listen 80" to "Listen 81".

That completes the configuration, phew!



Lets start "httpd" as: