Figure 2, “Process Flow for Entry-Balancing Directory Proxy Server” describes how a client request is treated in an entry-balancing deployment.
Entry balancing is typically used when the data set it too large to fully cache on a single server or when the write performance requirements of an environment are higher than can be achieved with a single replicated set of servers. In such cases, the data may be split across multiple sets of servers, increasing the memory available for caching and the overall write performance in proportion to the number of server sets.
As with a simple proxy deployment, the client request is first processed by the client connection policy, which determines how the Directory Proxy Server communicates with a set of clients. It contains a subtree view that represents the base DN for the entire deployment. The data set splits beneath this base DN.
The request is then passed to the entry-balancing request processor. The entry-balancing request processor contains a global attribute index property, which helps the request processor determine which server set contains the entry and how to properly route the request. It also contains a placement algorithm, which helps it select the server set in which to place new entries created by add requests.
Beneath the entry-balancing request processor are multiple proxying request processors that handle multiple unique sets of data. These request processors pass the request to a load-balancing algorithm, which determines which LDAP external server should handle the request. As with a simple proxy deployment, this LDAP external server contains properties that define the server’s location and the health checks used to determine if the server is functioning properly.
For information about entry-balancing replication, see Overview of Replication in an Entry-Balancing Environment.