Memory-to-memory session partitioning

Session partitioning gives the administrator the ability to filter or reduce the number of destinations that the session object gets sent to by the replication service. We can also configure session partitioning by specifying the number of replicas on the replication domain. The single replica option is chosen by default. Since the number of replicas is global for the entire replication domain, all the session managers connected to the replication domain use the same setting.

Single replica

We can replicate a session to only one other server, creating a single replica. When this option is chosen, a session manager picks another session manager that is connected to the same replication domain to replicate the HTTP session to during session creation. All updates to the session are only replicated to that single server. This option is set at the replication domain level. When this option is set, every session manager connected to this replication domain creates a single backup copy of HTTP session state information on a backup server.

Entire domain

Each object is replicated to every application server configured as a consumer of the replication domain. However, in the peer-to-peer mode, this topology is the most redundant because all servers replicate to each other, and as we add servers, more processors and memory are needed to manage replication. Entire domain is most useful for dynamic caching replication. Redundancy does not affect the client/server mode because clients replicate only to servers that are set to server mode. : Do not use entire domain in a large topology, as the infrastructure cannot handle the large number of connections necessary to support this configuration.

Specific number of replicas

We can specify a specific number of replicas for any entry created in the replication domain. The number of replicas is the number of application servers to replicate in the domain. This option eliminates redundancy that occurs in a full group replica, and also provides additional backup over a single replica. In peer-to-peer mode, the number of replicas cannot exceed the total number of application servers in the cluster. In the client/server mode, the number of replicas cannot exceed the total number of application servers in the cluster that are set to server mode.

On multiple application server nodes, the number of replicas must match the number of application servers on a node to ensure that a backup exists on a different node. For example, if we have two nodes with three application servers on each node, you would want to set the number of replicas to three. Location of backups is randomly selected and in a worse case scenario, the application server backups might be selected on the same node. Setting number of replicas to three ensures that at least one backup exists on a different node.

Node A has application servers A1, A2, and A3. Node B has application servers B1, B2, and B3. If A1 selects its backups to be on A2 and A3, then it is forced to select an application server on node B because number of replicas is set to three.

Related concepts

Memory-to-memory replication

Data replication

Data replication domain settings

Replication domain collection