Replicate data across appservers in a cluster


 

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Use this task to configure a data replication domain to transfer data, objects, or events for...

Data replication domains use the data replication service (DRS), which is an internal component that performs replication services, including replicating data, objects, and events among appservers.

Determine if we are using a multi-broker replication domain. If we configured a data replication domain with a previous version of WAS ND, we might be using a multi-broker replication domain. Any replication domains created with the current version of WAS are data replication domains. You should migrate any multi-broker replication domains to data replication domains.

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.

If we select...

Set HTTP memory-to-memory replication

...when creating a cluster, the replication domain is automatically created for you.

Similarly if, instead of WAS01Network , the cell name is simply WAS1, we have to pad the high level qualifier with the first three characters of the string DRSSTREAM. The high level qualifier then becomes WAS1DRS.

Complete the following steps to define two logstreams for an application on which DRS uses RLS for data replication.

  1. 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

      On this page we can specify the properties for the replication domain, including timeout, encryption, and number of replicas.

    • Create a replication domain when creating a cluster.

      To create a replication domain when creating a cluster, click...

      Servers | Clusters | Clusters | New

      Then click Set 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 the replication domain properties, click...

      Environment | Replication domains | replication_domain_name

  2. Set 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 replication domain and dynamic cache uses a different replication domain. However, use one replication domain if we 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 appservers.

  3. Determine whether the configuration requires additional thread resources.

    The replication service uses threads obtained from the Default thread pool for various tasks, including processing messages. Other appserver components also use this thread pool. Therefore, during appserver 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 appserver. The number of messages to be processed increases as the number of appservers in the domain increases and/or the number of replication consumers increases.

    Persistent data not being replicated to the appservers during server startup might be an indication that we 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 appservers in a replication domain is greater ten and the number of replication domain consumers in each appserver is greater than two, it might have to set the maximum thread pool size to a value greater than 40.

 

Next steps

If we 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...

Environment | Replication domains | replication_domain

...and click Regenerate encryption key to regenerate the key. After the key is regenerated, restart all of the appservers that are configured as part of the replication domain. Periodically regenerating the key improves data security.


Replication
Replication domain collection
Migrate servers from multi-broker replication domains to data replication domains
Delete replication domains
Replicating data with a multi-broker replication domain

 

Related tasks

Set core group memory utilization
Create clusters
Set cache replication
Set memory-to-memory replication for the peer-to-peer mode (default memory-to-memory replication)
Enable stateful session bean failover with the EJB container panel
Replicating SIP sessions

 

Related

Data replication domain settings
Thread pool settings
Data replication domains