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
- 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.
- From the administrative console, create a new generic server
cluster. Select .
- Provide a name, select a protocol, and click OK.
- Click the newly-created generic server cluster, and click Ports.
- 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.
- Repeat step 5 for each ODR in the cell that the generic
server cluster represents.
- Repeat steps 1 through 5 for each cell in your topology.
- Click Save to save your configuration changes.
- 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 . 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.