Help on Coherence + Weblogic Cluster configuration

Question

Hi,
I am new to Coherence. I am exploring coherence to fulfill one of my requirement.
My requirement : I have an application deployed on a Web logic Server clustered environment. I need to cache the application specific data(java maps) and that should be available for all nodes of the WLS cluster. The application data that's being cached, can be updated from any of the node from the WLS cluster and updated application data from the cache should be available for all the nodes of the WLS cluster. The nodes in the WLS cluster resides in different machines from different locations.
Can I use coherence as a caching services for my requirement?
If Yes, do I need to start a coherence cache server on each node of the WLS cluster?
If yes, do I need to specially configure these cache servers, so that these cache servers would communicate each other in case of any data updates in the cache?
It will be great help if you could also provide sample configurations to achieve the above scenarios.
Thanks in advance!
regards,
Srinivas M

Answer 1

You can start one cache server in the network by using for example
# home directory
BEA_HOME="/home/oracle/bea"
export BEA_HOME
# java vendor (for example Oracle or Sun)
JAVA_VENDOR="Oracle"
export JAVA_VENDOR
# cache server klasse
CACHE_SERVER_CLASS="com.tangosol.net.DefaultCacheServer"
export CACHE_SERVER_CLASS
# coherence options
COHERENCE_OPTIONS="-Dtangosol.coherence.management=all"
export COHERENCE_OPTIONS
COHERENCE_OPTIONS="${COHERENCE_OPTIONS} -Dtangosol.coherence.management.remote=true"
#COHERENCE_OPTIONS="${COHERENCE_OPTIONS} -Dtangosol.coherence.cacheconfig=WEB-INF/classes/session-cache-config.xml"
#COHERENCE_OPTIONS="${COHERENCE_OPTIONS} -Dtangosol.coherence.session.localstorage=true"
WL_HOME="${BEA_HOME}/wlserver_10.3"
export WL_HOME
BEA_JAVA_HOME="${BEA_HOME}/jrockit_160_05_R27.6.2-20"
export BEA_JAVA_HOME
SUN_JAVA_HOME="${BEA_HOME}/jdk160_11"
export SUN_JAVA_HOME
if [ "${JAVA_VENDOR}" = "Oracle" ]; then
     JAVA_HOME="${BEA_JAVA_HOME}"
     export JAVA_HOME
     MEM_ARGS="-jrockit -Xms512m -Xmx512m -Xss128k -Xgcprio:throughput"
     export MEM_ARGS
fi
if [ "${JAVA_VENDOR}" = "Sun" ]; then
     JAVA_HOME="${SUN_JAVA_HOME}"
     export JAVA_HOME
     MEM_ARGS="-server -Xmx512m -Xms512m -Xmn256m -Xss128k -XX:PermSize=128m -XX:MaxPermSize=128m -XX:+UseParallelGC -XX:ParallelGCThreads=2 -XX:+UseParallelOldGC -XX:+AggressiveOpts -XX:+UseBiasedLocking"
     export MEM_ARGS
fi
# classpath for the cache server
CLASSPATH="${WL_HOME}/coherence/coherence.jar"
export CLASSPATH
# start the cache server
${JAVA_HOME}/bin/java ${MEM_ARGS} ${COHERENCE_OPTIONS} ${CACHE_SERVER_CLASS}The -Dtangosol.coherence.management=all option gives you some handy information on what the cache is doing by using for example the mbean browser provided by jconsole or jrockit mission control.
You can create an application in which you create a cache, the following shows an example of a servlet
import com.tangosol.net.CacheFactory;
import com.tangosol.net.NamedCache;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.Random;
public class TestServlet extends HttpServlet {
    private NamedCache movies;
    public void init() throws ServletException {
        movies = CacheFactory.getCache("repl-movies");
        movies.put(10, new Movie(10, "Rear Window", "Alfred Hitchcock"));
        movies.put(20, new Movie(20, "Vertigo", "Alfred Hitchcock"));
        movies.put(30, new Movie(30, "Double Indemnity", "Billy Wilder"));
        movies.put(40, new Movie(40, "Touch of Evil", "Orson Welles"));
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        Integer[] integers = {10, 20, 30, 40};
        Random random = new Random();
        while (true) {
            movies.get(integers[random.nextInt(4)]);
}Package the servlet into for example a WAR file and deploy it to a configured WebLogic cluster.
By accessing servlet on the different nodes of the cluster a new cache gets created and added to the
already running DefaultServer.
The hard part is to configure your cache. As you can see in the servlet init we ue something like CacheFactory.getCache("repl-movies");
Coherence default with some example cache configurations which are contained in the coherence.jar (coherence-cache-config.xml).
The following entry is used
<cache-mapping>
      <cache-name>repl-*</cache-name>
      <scheme-name>example-replicated</scheme-name>
</cache-mapping>
<replicated-scheme>
      <scheme-name>example-replicated</scheme-name>
      <service-name>ReplicatedCache</service-name>
      <backing-map-scheme>
        <local-scheme>
          <scheme-ref>unlimited-backing-map</scheme-ref>
        </local-scheme>
      </backing-map-scheme>
      <autostart>true</autostart>
</replicated-scheme>A replicated cache is probably what you need as well. As you want all the data to be available on all nodes. If you want to use
your own cache configuration you can add the option -Dtangosol.coherence.cacheconfig (see the start script for the default server)
A good introduction on Coherence can be found here:
http://www.packtpub.com/article/installing-coherence-3.5-and-accessing-the-data-grid-1
and
http://www.packtpub.com/article/installing-coherence-3.5-and-accessing-the-data-grid-2?utm_source=rk_coherence_abr1_0310&utm_medium=content&utm_campaign=ramsai