6.5 Configuring an Oracle WebLogic Server Cluster as an Origin-Server Pool

Note:

Oracle Traffic Director has built-in support for some common functionality offered by the WebLogic Server plug-in. Hence Oracle Traffic Director does not require any other plug-in to inter-operate with WebLogic Server.

If you want to create an origin-server pool that represents a cluster of Oracle WebLogic Server managed servers, you need not specify each managed server in the cluster as an origin server. It is sufficient to specify any one of the managed servers as the sole origin server in the pool. You can configure Oracle Traffic Director to discover the presence of other Oracle WebLogic Server instances in the cluster dynamically, and distribute client requests to the managed server that is configured as an origin server and to the dynamically discovered managed servers in the same cluster.

So when dynamic discovery is enabled, if any of the managed servers in the cluster is stopped, added, or removed, you need not update the definition of the origin-server pool. However, for detecting changes in the Oracle WebLogic Server cluster, Oracle Traffic Director sends health-check requests at a specified interval, which causes some overhead.

6.5.1 How Dynamic Discovery Works

When dynamic discovery is enabled for an origin-server pool, Oracle Traffic Director discovers the remaining Oracle WebLogic Server managed servers in the cluster, by doing the following:

When an Oracle Traffic Director instance starts, it checks whether the origin servers specified in the pool are Oracle WebLogic Server managed servers and whether the servers belong to a cluster, by sending an HTTP health-check request to each configured origin server.

The origin server's response indicates whether the server is an Oracle WebLogic Server managed server. If the origin server is an Oracle WebLogic Server managed server that belongs to a cluster, the response also includes a list of the managed servers in the cluster.
Oracle Traffic Director uses the information in the response from the origin server to update the configuration with the discovered managed servers.

The dynamically discovered origin servers inherit all of the properties—weight, maximum connections, and so on—that are specified for the configured origin server.
Subsequently, at each health-check interval (default: 30 seconds) configured for the origin-server pool, Oracle Traffic Director attempts to detect changes in the cluster, by sending dynamic-discovery health-check requests to the Oracle WebLogic Server instances that are configured as origin servers in the pool.

If the response indicates a change—removal or addition of a managed server—in the cluster since the previous health check, Oracle Traffic Director updates the configuration with the new set of dynamically discovered origin servers.

Note:

Dynamically discovered origin servers are not stored permanently in the origin-server pool definition of the instance's configuration. So when you restart an Oracle Traffic Director instance, the process of dynamic discovery starts afresh.
The HTTP request type that Oracle Traffic Director sends for dynamic discovery is the health-check request type that is currently configured for the origin-server pool—OPTIONS (default) or GET. For more information, see Section 14.3, "Configuring Health-Check Settings for Origin-Server Pools."

6.5.2 Enabling Dynamic Discovery

When you create an origin-server pool, dynamic discovery of Oracle WebLogic Server managed servers in a cluster is not enabled by default. You can enable dynamic discovery by using either the administration console or the CLI.

Note:

When you modify an origin-server pool, you are, in effect, modifying a configuration. So for the updated origin-server pool settings to take effect in the Oracle Traffic Director instances, you should redeploy the configuration as described in Section 4.3, "Deploying a Configuration."
The CLI examples in this section are shown in shell mode (tadm>). For information about invoking the CLI shell, see Section 2.3.1, "Accessing the Command-Line Interface."

Enabling Dynamic Discovery Using the Administration Console

To enable dynamic discovery of WebLogic Server managed servers in a cluster by using the administration console, do the following:

Log in to the administration console, as described in Section 2.3.2, "Accessing the Administration Console."
Click the Configurations button that is situated at the upper left corner of the page.

A list of the available configurations is displayed.
Select the configuration for which you want to enable dynamic discovery.
In the navigation pane, expand Server Pools and select the origin-server pool for which you want to enable dynamic discovery.

The Server Pool Settings page is displayed.
Go to the Advanced Settings section of the page.
Under the Health Check subsection, make sure that the Protocol is HTTP, select the Dynamic Discovery check box.
Click Save.

Note:

If the current health-check protocol is TCP, an error message is displayed indicating that the protocol must be changed to HTTP in order to enable dynamic discovery.

A message is displayed in the Console Message pane confirming that the updated health-check settings were saved.

In addition, the Deployment Pending message is displayed at the top of the main pane. You can either deploy the updated configuration immediately by clicking Deploy Changes, or you can do so later after making further changes, as described in Section 4.3, "Deploying a Configuration."

Enabling Dynamic Discovery Using the CLI

To enable dynamic discovery of Oracle WebLogic Server managed servers in a cluster, run the set-health-check-prop command.

For example, the following command enables dynamic discovery of managed servers in the Oracle WebLogic Server cluster that the wls-1 origin-server pool represents.

tadm> set-health-check-prop --config=soa.example.com --origin-server-pool=wls-1 dynamic-server-discovery=true
OTD-70201 Command 'set-health-check-prop' ran successfully.

Note:

If the current health-check protocol is TCP, an error message is displayed indicating that the protocol must be changed to HTTP in order to enable dynamic discovery.

For the updated configuration to take effect, you should deploy it to the Oracle Traffic Director instances by using the deploy-config command.

For more information about set-health-check-prop, see the Oracle Traffic Director Command-Line Reference or run the command with the --help option.