Defining generic server clusters for remote ODR cells

When you are configuring the on demand router (ODR) to route to other cells for a cell affinity, failover, or forwarding topology, you must define generic server clusters to represent those cells. The purpose of defining generic server clusters is to allow each ODR to recognize the other ODRs that are in remote cells. If you are using the core group bridge or bulletin board to route between cells, you do not need to complete these steps.

About this task

By defining the generic server clusters (GSC) , the ODRs in one cell to send traffic to the ODRs in the other cell. There are several reasons why this is important.
  • If all the application servers in a cell are unavailable, the ODRs in that cell need to send requests somewhere. The ODRs send the requests to the GSC, which represents the ODRs in the other cell. The ODRs in the other cell then route the requests to application servers in their own cell, ensuring that the requests are handled successfully.
  • If a request with session data that is associated with an application server in Cell1 is mistakenly sent to an ODR in Cell2, the ODR in Cell2 needs to be able to forward the request to an ODR in Cell1, as only the ODRs in Cell1 can send the request to the appropriate application server. The ODRs in Cell2 cannot send requests directly to an application server in Cell1. The GSC is used to allow the ODR in Cell2 to forward the request to an ODR in Cell1, which handles the request.

Procedure

  1. Configure trusted proxies. Each ODR must include all of the other ODRs (including those in remote cells), Web servers, and IBM HTTP Server (IHS) servers that send traffic to this ODR as trusted proxies. Follow the WebSphere Application Server Network Deployment instructions in the Proxy server settings topic for most of the instructions to configure ODRs. See Configuring ODRs for WebSphere Virtual Enterprise specific fields.
  2. From the administrative console, create a new generic server cluster. Select Servers > Generic Server Clusters > New.
  3. Provide a name, select a protocol, and click OK.
  4. Click the newly-created generic server cluster, and click Ports.
  5. Click New, and specify the host name and port number of the ODR as the member of the generic server cluster.

    The ODR normally calculates the cloneID for a server from the host name and the non-SSL ODR port. This same mechanism is used to calculate GSC member cloneIDs. Thus, when an ODR in one cell is represented by a GSC member in another cell, the cloneIDs automatically match. However, you can use an override mechanism to specify the cloneID manually. To specify the cloneID manually, define a custom GSC member property named ODRCloneId with the value set to the desired cloneID. This value must match the calculated cloneID of the ODR in the remote cell.

  6. Repeat step 5 for each ODR in the cell that the generic server cluster represents.
  7. Repeat steps 1 through 5 for each cell in your topology.
  8. Click Save to save your configuration changes.
  9. Optional: If multiple servers or nodes share the same host, and therefore the same host name, you must define custom properties to ensure the proper routing of requests to generic server clusters. In the administrative console, you can set these custom properties by clicking Servers > Generic server clusters > gsc_name > Additional properties > Ports > Custom properties > New. Use the following descriptions to define the name and value of the properties:
    • server custom property: When you are defining GSC members in which more than one GSC member, including members in different GSCs, reside on the same node (have the same host name), you must define the server custom property on the GSC member definition to ensure uniqueness of the GSC member names in the ODC. Without this custom property, the GSC member name is based on the configured host name, which is not unique for two members on the same node and results in improper routing. With this property, the GSC member name is the value that is provided in the custom property.
    • node custom property: Set this property when multiple nodes are sharing the same host name. The value of this property explicitly specifies the node name to which the host name and port correspond.

Results

By configuring the GSC representations of the ODRs in the remote cell, traffic that was wrongly routed to one cell can be forwarded to the correct cell, maintaining cell affinity. Configuring GSC representations does not enable failover, so if an ODR has no available servers in its cell, the request cannot be serviced. To enable the ODR to send the request to an application server in a remote cell when no local servers are available, see Configuring the on demand router for multi-cluster failover and load balancing routing.


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