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## Chapter 18. Workbench High Availability

### 18.1.1. VFS clustering

The VFS repositories (usually git repositories) stores all the assets (such as rules, decision tables, process definitions, forms, etc). If that VFS resides on each local server, then it must be kept in sync between all servers of a cluster.

Use Apache Zookeeper and Apache Helix to accomplish this. Zookeeper glues all the parts together. Helix is the cluster management component that registers all cluster details (nodes, resources and the cluster itself). Uberfire (on top of which Workbench is build) uses those 2 components to provide VFS clustering.

To create a VFS cluster:

1. Download Apache Zookeeper and Apache Helix.

2. Install both:

   1. Unzip Zookeeper into a directory (`$ZOOKEEPER_HOME`).

   2. In `$ZOOKEEPER_HOME`, copy `zoo_sample.conf` to `zoo.conf`

   3. Edit `zoo.conf`. Adjust the settings if needed. Usually only these 2 properties are relevant:

          # the directory where the snapshot is stored.
          dataDir=/tmp/zookeeper
          # the port at which the clients will connect
          clientPort=2181

   4. Unzip Helix into a directory (`$HELIX_HOME`).

3. Configure the cluster in Zookeeper:

   1. Go to its `bin` directory:

          $ cd $ZOOKEEPER_HOME/bin

   2. Start the Zookeeper server:

          $ sudo ./zkServer.sh start

      If the server fails to start, verify that the `dataDir` (as specified in `zoo.conf`) is accessible.

   3. To review Zookeeper's activities, open `zookeeper.out`:

          $ cat $ZOOKEEPER_HOME/bin/zookeeper.out

4. Configure the cluster in Helix:

   1. Go to its `bin` directory:

          $ cd $HELIX_HOME/bin

   2. Create the cluster:

          $ ./helix-admin.sh --zkSvr localhost:2181 --addCluster kie-cluster

      The `zkSvr` value must match the used Zookeeper server. The cluster name (`kie-cluster`) can be changed as needed.

   3. Add nodes to the cluster:

          # Node 1
          $ ./helix-admin.sh --zkSvr localhost:2181 --addNode kie-cluster nodeOne:12345
          # Node 2
          $ ./helix-admin.sh --zkSvr localhost:2181 --addNode kie-cluster nodeTwo:12346
          ...

      Usually the number of nodes a in cluster equal the number of application servers in the cluster. The node names (`nodeOne:12345` , ...) can be changed as needed.

      ## Note

      `nodeOne:12345` is the unique identifier of the node, which will be referenced later on when configuring application servers. It is not a host and port number, but instead it is used to uniquely identify the logical node.

   4. Add resources to the cluster:

          $ ./helix-admin.sh --zkSvr localhost:2181 --addResource kie-cluster vfs-repo 1 LeaderStandby AUTO_REBALANCE

      The resource name (`vfs-repo`) can be changed as needed.

   5. Rebalance the cluster to initialize it:

          $ ./helix-admin.sh --zkSvr localhost:2181 --rebalance kie-cluster vfs-repo 2

   6. Start the Helix controller to manage the cluster:

          $  ./run-helix-controller.sh --zkSvr localhost:2181 --cluster kie-cluster 2>&1 > /tmp/controller.log &

5. Configure the security domain correctly on the application server. For example on WildFly and JBoss EAP:

   1. Edit the file `$JBOSS_HOME/domain/configuration/domain.xml`.

      For simplicity sake, presume we use the default domain configuration which uses the profile `full` that defines two server nodes as part of `main-server-group`.

   2. Locate the profile `full` and add a new security domain by copying the other security domain already defined there by default:

          <security-domain name="kie-ide" cache-type="default">
              <authentication>
                   <login-module code="Remoting" flag="optional">
                       <module-option name="password-stacking" value="useFirstPass"/>
                   </login-module>
                   <login-module code="RealmDirect" flag="required">
                       <module-option name="password-stacking" value="useFirstPass"/>
                   </login-module>
              </authentication>
          </security-domain>

      ## Important

      The security-domain name is a magic value.

6. Configure the system properties for the cluster on the application server. For example on WildFly and JBoss EAP:

   1. Edit the file `$JBOSS_HOME/domain/configuration/host.xml`.

   2. Locate the XML elements `server` that belong to the `main-server-group` and add the necessary system property.

      For example for nodeOne:

          <system-properties>

            <property name="jboss.node.name" value="nodeOne" boot-time="false"/>

            <property name="org.uberfire.nio.git.dir" value="/tmp/kie/nodeone" boot-time="false"/>

            <property name="org.uberfire.metadata.index.dir" value="/tmp/kie/nodeone" boot-time="false"/>

            <property name="org.uberfire.cluster.id" value="kie-cluster" boot-time="false"/>

            <property name="org.uberfire.cluster.zk" value="localhost:2181" boot-time="false"/>

            <property name="org.uberfire.cluster.local.id" value="nodeOne_12345" boot-time="false"/>

            <property name="org.uberfire.cluster.vfs.lock" value="vfs-repo" boot-time="false"/>

            <!-- If you're running both nodes on the same machine: -->

            <property name="org.uberfire.nio.git.daemon.port" value="9418" boot-time="false"/>

          </system-properties>

      And for nodeTwo:

          <system-properties>

            <property name="jboss.node.name" value="nodeTwo" boot-time="false"/>

            <property name="org.uberfire.nio.git.dir" value="/tmp/kie/nodetwo" boot-time="false"/>

            <property name="org.uberfire.metadata.index.dir" value="/tmp/kie/nodetwo" boot-time="false"/>

            <property name="org.uberfire.cluster.id" value="kie-cluster" boot-time="false"/>

            <property name="org.uberfire.cluster.zk" value="localhost:2181" boot-time="false"/>

            <property name="org.uberfire.cluster.local.id" value="nodeTwo_12346" boot-time="false"/>

            <property name="org.uberfire.cluster.vfs.lock" value="vfs-repo" boot-time="false"/>

            <!-- If you're running both nodes on the same machine: -->

            <property name="org.uberfire.nio.git.daemon.port" value="9419" boot-time="false"/>

          </system-properties>

      Make sure the cluster, node and resource names match those configured in Helix.

### 18.1.2. jBPM clustering

In addition to the information above, jBPM clustering requires additional configuration. See this blog post to configure the database etc correctly.

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