coherence-operator

Access JMX in the Coherence Cluster Using JConsole and VisualVM

Java Management Extensions (JMX) is the standard way to inspect and manage enterprise Java applications. Applications that are exposed via JMX do not incur runtime performance penalty for doing so unless a tool is actively connected to the JMX connection, and only then in certain cases. The Java Tutorials provide introduction to JMX.

The Coherence documentation describes how to use JMX with Coherence.

All the capabilities of JMX with Coherence are also available with the operator.

This sample shows how to connect to a Coherence JMX MBean Server when using the Coherence Operator. The option --set store.jmx.enabled=true is used which creates an MBean Server pod from which you can connect to the operator.

By default, there is one replica for the MBean Server. You can create more MBean server pods by setting the store.jmx.replicas value. For example, --set store.jmx.replicas=2.

See here for information about connecting to Management over REST endpoint.

Return to Management samples / Return to samples

Prerequisites

Install the Coherence Operator

Ensure you have installed the Coherence Operator using the instructions here.

Download the JMXMP connector JAR

The JMX endpoint does not use RMI, instead it uses JMXMP. This requires an additional JAR on the classpath of the Java JMX client (VisualVM and JConsole). You can use curl to download the required JAR.

curl http://central.maven.org/maven2/org/glassfish/external/opendmk_jmxremote_optional_jar/1.0-b01-ea/opendmk_jmxremote_optional_jar-1.0-b01-ea.jar \
     -o opendmk_jmxremote_optional_jar-1.0-b01-ea.jar

This also can be downloaded as a Maven dependency if you are connecting through a Maven project.

<dependency>
   <groupId>org.glassfish.external</groupId>
   <artifactId>opendmk_jmxremote_optional_jar</artifactId>
   <version>1.0-b01-ea</version>
</dependency>

Installation Steps

Install the Coherence cluster

Install the cluster with one MBean server pod:
```
$ helm install \
   --namespace sample-coherence-ns \
   --name storage \
   --set clusterSize=3 \
   --set cluster=coherence-cluster \
   --set imagePullSecrets=sample-coherence-secret \
   --set logCaptureEnabled=false \
   --set store.jmx.enabled=true \
   --set store.jmx.replicas=1 \
   coherence/coherence
```
Note: There are many other store.jmx.* options which control other aspects of the MBean Server node. Refer to the Coherence Operator values.yaml file for more information.

After the chart is installed, instructions are displayed to help you utilize this feature. You can follow these instructions or use the commands.

Check whether the MBean server pod is running:

 $ kubectl get pods -n sample-coherence-ns

 NAME                                    READY   STATUS    RESTARTS   AGE
 coherence-operator-5899f6444b-tckm4     1/1     Running   0          1h
 storage-coherence-0                     1/1     Running   0          29m
 storage-coherence-1                     1/1     Running   0          28m
 storage-coherence-2                     1/1     Running   0          27m
 storage-coherence-jmx-54f5d779d-svh29   1/1     Running   0          29m

A pod prefixed with storage-coherence-jmx is displayed in the output.

Port forward the MBean server pod:

$ export POD_NAME=$(kubectl get pods --namespace sample-coherence-ns -l "app=coherence,release=storage,component=coherenceJMXPod" -o jsonpath="{.items[0].metadata.name}")

$ kubectl --namespace sample-coherence-ns port-forward $POD_NAME 9099:9099

Access the JMX endpoint at the URL service:jmx:jmxmp://127.0.0.1:9099.

(Optional) Add data to a cache

Connect to the Coherence console and create a cache:

Note: If you do not carry out this step, then you will not see any CacheMBeans as described below.
```
$ kubectl exec -it --namespace sample-coherence-ns storage-coherence-0 bash /scripts/startCoherence.sh console
```
At the Map (?): prompt, type cache test. This will create a cache in the service PartitionedCache.

Use the following to add 100,000 objects of size 1024 bytes, starting at index 0 and using batches of 100.
```
bulkput 100000 1024 0 100

Mon Apr 15 07:37:03 GMT 2019: adding 100000 items (starting with #0) each 1024 bytes ...
Mon Apr 15 07:37:15 GMT 2019: done putting (11578ms, 8878KB/sec, 8637 items/sec)
```
At the prompt, type size and it should show 100000.

Then, type bye to exit the console.
Access through JConsole

Ensure you run JConsole with the JMXMP connector on the classpath:
```
$ jconsole -J-Djava.class.path="$JAVA_HOME/lib/jconsole.jar:$JAVA_HOME/lib/tools.jar:opendmk_jmxremote_optional_jar-1.0-b01-ea.jar" service:jmx:jmxmp://127.0.0.1:9099
```
In the console UI, select the MBeans tab and then Coherence Cluster attributes. You should see the Coherence MBeans as below:
Access through VisualVM

Ensure you run VisualVM with the JMXMP connector on the classpath:
```
$ jvisualvm -cp "$JAVA_HOME/lib/tools.jar:opendmk_jmxremote_optional_jar-1.0-b01-ea.jar" 
```
Note: If you have downloaded VisualVM separatley, then the executable is visualvm.

From the Applications tab in the VisualVM UI, right-click on Local and select Add JMX Connection.

Enter service:jmx:jmxmp://127.0.0.1:9099 for Connection and click OK.

A JMX connection is added. Double-click to open the new connection. You can see the Coherence MBeans under the MBeans tab. If you have installed the Coherence VisualVM plugin, you can also see a Coherence tab.

JVisualVM

Refer to the Coherence MBean Reference for detailed information about Coherence MBeans.

Uninstall the Charts

Use the following command to delete the chart installed in this sample:

$ helm delete storage --purge

Before starting another sample, ensure that all the pods are removed from previous samples.

If you want to remove the coherence-operator, then include it in the helm delete command.

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