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SAP Sourcing implements a basic clustering scheme for application scaling and load balancing. A cluster is a logical group of SAP Sourcing services. Clusters are primarily used to define how end users access the SAP Sourcing application. For example, you might configure one cluster for purchasers and another for suppliers. These two groups normally use different hosts and authentication methods. Clusters facilitate this kind of flexibility.

Clusters also are involved with managing performance. The clusters in SAP Sourcing include the ability to balance user load across all member services.

Clustering is often provided by the application server platform, for example, BEA WebLogic or IBM WebSphere. SAP Sourcing implements a native clustering solution for two principal reasons: to allow cluster support when deployed on application servers that do not offer clustering, and to address conflicts that exist between application server clustering, SSL encryption, and SAP Sourcing session management requirements.

The System Default Cluster

A default cluster is created when the SAP Sourcing software is installed. When the application cannot determine which cluster a user is attempting to access, the user is placed in the default cluster.

There is no single strategy for using the default cluster. Some possible scenarios include:

  • Lock Down: Create specific application clusters and deactivate the default. This will ensure that unrecognized requests are never forwarded to an active service.

  • Administration: It may be convenient to map the default cluster to a URL used only internally by administrators. This provides administrators with a recovery path if the configured clusters are set up incorrectly and cannot be accessed.

  • Simple: Map all application contexts to the default cluster. The easiest of all configurations, this ensures that all requests will always be mapped to a single cluster. This is also the most limiting configuration. It is not suitable in the following situations:

    • When using multiple sourcing contexts

    • When using different network configurations for purchasers and sellers

    • When using more than one buy-side or sell-side LDAP directory

Note Note

It is almost always helpful to change the Hostname field of the default cluster. When the product is installed, it is set to "!!DEFAULT!!". This is a special value that includes everything. Leaving it set to this default can hide configuration problems because it will appear that host mapping is working correctly, even when it is not.

End of the note.

A cluster configuration can support a single buy-side directory and a single sell-side directory. To support multiple directories, you define multiple cluster configurations. For more information about directories, see Directory Configuration.

Load Balancing

The SAP Sourcing load balancing capability provides the ability to distribute user load across a set of servers that are members of a cluster. Implementation of this capability enables an additional load balancing step when a user submits credentials in order to log into the system. Load Balancing during the actual user login results in an accurate determination of the actual load on each member of the load balancing cluster at that point.

To enable this enhanced load balancing capability, all hosts in a load balancing cluster must have fully defined DNS domain names and must reside in the same DNS domain.

For example, if a cluster contains two cluster members, server1 and server2:

  • Both servers must reside in the same DNS domain (for example, biogenyx.com).

  • Both servers must be identifiable on the network by their full DNS domain names (for example, server1.biogenyx.com and server2.biogenyx.com) in their respective Cluster Member's External Address field.

  • The domain name must be configured in the Cluster object. Successfully configuring the domain name in the Cluster Object is the 'switch' that turns on the enhanced load balancing.

Note that this capability will not be enabled by default upon upgrading from earlier releases. Minimally, system administrators will need to update the clusters used in the implementation to specify the correct domain name. In addition, it is possible that the cluster hosts will need to be properly configured to be recognizable on the local network using a full DNS domain name and the host's associated Cluster Member's External Address updated to reflect the hosts full DNS name.

This section describes how to create and edit a cluster configuration.