Use this task to configure a data replication domain to transfer
data, objects, or events for session manager, dynamic cache, or stateful session
beans. Data replication domains use the data replication service (DRS), which
is an internal product component that performs replication services, including
replicating data, objects, and events among application servers.
About this task
Use this task to configure
replication, a service that transfers
data, objects, or events among the application servers in a cluster. Use replication
to prevent loss of session data with session manager, to further improve the
performance of the dynamic cache service, and to provide failover in stateful
session beans. For more information about replication, see
Replication.
Avoid trouble: If you select the
Configure HTTP memory-to-memory
replication option when you create a cluster, the replication domain is
automatically created for you.
gotcha
Procedure
- Create a replication domain. Use one of the following
methods to create a replication domain:
- Create a replication domain manually.
To create a replication
domain manually without creating a new cluster, click Environment > Replication
domains > New in the administrative console.
On this page you can
specify the properties for the replication domain, including timeout, encryption,
and number of replicas. See Data replication domain settings for more information about the properties that you
can configure for your replication domain.
- Create a replication domain when you create a cluster.
To
create a replication domain when you create a cluster, click Servers >
Clusters > New in the administrative console. Then click Configure
HTTP memory-to-memory replication. The replication domain that is created
has the same name as the cluster and has the default settings for a replication
domain. The default settings for a replication domain are to create a single
replica of each piece of data and to have encryption disabled. To modify these
replication domain properties, click Environment > Replication domains
> replication_domain_name in the administrative console.
For more information about the replication domain settings
that you can configure in the administrative console, see Data replication domain settings
- Configure the consumers, or the components that use the replication
domains. Dynamic cache, session manager, and stateful session
beans are the three types of replication domain consumers. Each type of consumer
must be configured with a different replication domain. For example, session
manager uses one domain and dynamic cache uses a different replication domain.
However, use one replication domain if you are configuring HTTP session memory-to-memory
replication and stateful session bean replication. Using one replication domain
in this case ensures that the backup state information of HTTP sessions and
stateful session beans are on the same application servers.
Determine whether your
configuration requires additional thread resources. The replication
service uses threads obtained from the Default thread pool for various tasks,
including processing messages. Other application server components also use
this thread pool. Therefore, during application server startup the default
maximum thread pool size of 20 might not be sufficient to allow the replication
service to obtain enough threads from the pool to process all of the incoming
replication messages. The number of incoming messages is influenced by the
number of application servers in the domain and the number of replication
domain consumers on each application server. The number of messages to be
processed increases as the number of application servers in the domain increases
and/or the number of replication consumers increases.
Persistent data
not being replicated to the application servers during server startup might
be an indication that you need to increase the setting for the maximum thread
pool size. In larger configurations, doubling the maximum size of the Default
thread pool to 40 is usually sufficient. However, if the number of application
servers in a replication domain is greater ten and the number of replication
domain consumers in each application server is greater than two, it might
have to set the maximum thread pool size to a value greater than 40. See Thread pool settings for a description of how to
change the maximum thread pool size setting.
Results
Data is replicating among the application servers in a configured
replication domain.
What to do next
If you select DES or 3DES as the encryption type for a replication
domain, an encryption key is used for the encryption of messages. At regular
intervals, for example once a month, you should go to the Environment >
Replication domains page in the administrative console, and click Regenerate
encryption key to regenerate the key. After the key is regenerated, you
must restart all of the application servers that are configured as part of
the replication domain. Periodically regenerating the key improves data security.