Client affinity is defined between a client connection and a data source. When client affinity is defined, requests from a specified client connection are distributed to a specified data source in a data source pool.
The client affinity feature reduces the risk of propagation delay in deployments that use load balancing. Propagation delays can occur when a client makes consecutive requests that target the same entry if those requests are not treated by the same data source. For example, a client might make one request to change an entry and a second request to use the changed entry. If the second request is treated by a data source that has not been updated by the first request, an error occurs.
Client affinity can be configured in the following ways:
Enabled or disabled
Configured for all write requests after the first write request
Configured for all requests after the first write request
Configured for all requests after the first read request or write request
Configured for first read request after a write request
Configured to expire after a specified time
Client affinity takes precedence over the load balancing algorithm. Directory Proxy Server distributes a request from the specified connection to the specified data source, irrespective of the load balancing algorithm.
If client affinity is defined and enabled, the load balancing algorithm takes precedence in the following circumstances:
The request that starts client affinity has not occurred
The request that ends client affinity has occurred
The client affinity time-out has expired
The specified data source cannot be used for a request, or an error has occurred on the specified data source
A data source cannot be used for a request in the following circumstances:
It is offline.
It is not configured to perform the operation being requested. For example, a data source that is configured for read requests cannot respond to write requests.
For information about how to configure client affinity, see Configuring Client Affinity in Sun Directory Server Enterprise Edition 7.0 Administration Guide.
The client affinity feature must be used to configure Directory Proxy Server as a simple, connection based router. For information, see Configuring Directory Proxy Server as a Connection Based Router in Sun Directory Server Enterprise Edition 7.0 Administration Guide.