Configuring And Building Managed

Overview of Coherence Clusters

Coherence clusters consist of multiple managed Coherence server instances that distribute data in-memory to increase application scalability, availability, and performance. An application interacts with the data in a local cache and the distribution and backup of the data is automatically performed across cluster members.

Coherence clusters are different than WebLogic Server clusters. They use different clustering protocols and are configured separately. Multiple WebLogic Server clusters can be associated with a Coherence cluster and a WebLogic Server domain typically contains a single Coherence cluster. Managed servers that are configured as Coherence cluster members are referred to as managed Coherence servers.

Managed Coherence servers can be explicitly associated with a Coherence cluster or they can be associated with a WebLogic Server cluster that is associated with a Coherence cluster. Managed Coherence servers are typically setup in tiers that are based on their type: a data tier for storing data, an application tier for hosting applications, and a proxy tier that allows external clients to access caches.

Define a Coherence Cluster Resource

To define a Coherence cluster resource:

1. From the WebLogic Server Administration Console Domain Structure pane, expand Environment and click Coherence Clusters.
2. From the Summary of Coherence Clusters page, click New.
3. From the Create a Coherence Cluster Configuration page, enter a name for the cluster using the Name field. Click Next.
4. From the Coherence Cluster Addressing section, select the clustering mode or keep the default settings. The default cluster listen port (7574) does not need to be changed for most clusters. For details on configuring the clustering mode, see Configure Cluster Communication.
5. From the Coherence Cluster Members section, click to select the managed Coherence servers or WebLogic Server clusters that are to be part of the Coherence cluster or skip this section if managed Coherence servers and WebLogic Clusters are yet to be defined.
6. Click Finish. The Summary of Coherence Clusters screen displays and the Coherence Clusters table lists the cluster resource.

Create Standalone Managed Coherence Servers

Managed Coherence servers are managed server instances that are associated with a Coherence cluster. Managed Coherence servers join together to form a Coherence cluster and are often referred to as cluster members. Cluster members have seniority and the senior member performs cluster tasks (for example, issuing the cluster heart beat).

1. Managed Coherence servers and standalone Coherence cluster members (those that are not managed within a WebLogic Server domain) can join the same cluster. However, standalone cluster members cannot be managed from within a WebLogic Server domain; operational configuration and application lifecycles must be manually administered and monitored.
2. The Administration Server is typically not used as a managed Coherence server in a production environment.

Managed Coherence servers are distinguished by their role in the cluster. A best practice is to use different managed server instances (and preferably different WebLogic Server clusters) for each cluster role.

1. storage-enabled – a managed Coherence server that is responsible for storing data in the cluster. Coherence applications are packaged as Grid ARchives (GAR) and deployed on storage-enabled managed Coherence servers.
2. storage-disabled – a managed Coherence server that is not responsible for storing data and is used to host Coherence applications (cache clients). A Coherence application GAR is packaged within an EAR and deployed on storage-disabled managed Coherence servers.
3. proxy – a managed Coherence server that is storage-disabled and allows external clients (non-cluster members) to use a cache. A Coherence application GAR is deployed on managed Coherence proxy servers.

To create managed Coherence servers:

1. From the WebLogic Server Administration Console Domain Structure pane, expand Environment and click Servers.
2. Click New to create a new managed server.
3. From the Create a New Server page, enter the server's properties as required.
4. Select whether to make the server part of a WebLogic Server cluster. For details on creating WebLogic Server clusters for use as a Coherence deployment tier, see Creating Coherence Deployment Tiers.
5. Click Finish. The Summary of Servers page displays and the new server is listed.
6. Select the new server to configure its settings.
7. From the Coherence tab, use the Coherence Cluster drop-down list and select a Coherence cluster to associate it with this managed server. By default, the managed server is a storage-enabled Coherence member as indicated by the Local Storage Enabled field. For details on changing managed Coherence settings, see Configuring Managed Coherence Servers.
8. Click Save. The Summary of Servers page displays.
9. From the Summary of Servers page, click the Control tab and start the server.

Creating Coherence Deployment Tiers

Coherence supports different topologies within a WebLogic Server domain to provide varying levels of performance, scalability, and ease of use. For example, during development, a single standalone managed server instance may be used as both a cache server and a cache client. The single-server topology is easy to setup and use, but does not provide optimal performance or scalability. For production, Coherence is typically setup using WebLogic Server Clusters. A WebLogic Server cluster is used as a Coherence data tier and hosts one or more cache servers; a different WebLogic Server cluster is used as a Coherence application tier and hosts one or more cache clients; and (if required) different WebLogic Server clusters are used for the Coherence proxy tier that hosts one or more managed Coherence proxy servers and the Coherence extend client tier that hosts extend clients. The tiered topology approach provides optimal scalability and performance.

The instructions in this section use both the Clusters Settings page and Servers Settings page in the WebLogic Server Administration Console to create Coherence deployment tiers. WebLogic Server clusters and managed servers instances can be associated with a Coherence cluster resource using the ClusterMBean and ServerMBean MBeans, respectively. Managed servers that are associated with a WebLogic Server cluster inherit the cluster's Coherence settings. However, the settings may not be reflected in the Servers Settings page.

Create a Coherence Data Tier

To create a Coherence data tier:

1. Create a WebLogic Server cluster. For details, see Chapter 10, "Setting up WebLogic Clusters."
2. From the Summary of Clusters page, select the cluster from the Clusters table to configure it.
3. From the Coherence tab, use the Coherence Cluster drop-down list and select a Coherence cluster to associate it with this WebLogic Server cluster. By default, the managed servers assigned to this WebLogic Server cluster will be storage-enabled Coherence members as indicated by the Local Storage Enabled field.

Create Managed Coherence Servers for a Data Tier

To create managed servers for a Coherence data tier:

1. From the WebLogic Server Administration Console Domain Structure pane, expand Environment and, click Servers.
2. Click New to create a new managed server.
3. From the Create a New Server page, enter the server's properties as required.
4. Click the Yes option to add the server to an existing cluster and use the drop-down list to select the data tier WebLogic Server cluster. The managed server inherits the Coherence settings from the data tier WebLogic Server cluster.
5. Click Finish. The Summary of Servers page displays and the new server is listed.
6. Repeat these steps to create additional managed servers as required.
7. From the Control tab, select the servers to start and click Start.