Replicate data across application servers in a cluster
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 component that performs replication services, including replicating data, objects, and events among application servers.
Determine if we are using a multi-broker replication domain. If we configured a data replication domain with a previous version of the product, we might be using a multi-broker replication domain. Any replication domains created with the current version of the product are data replication domains. We should migrate any multi-broker replication domains to data replication domains.
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.
If we select the opiton...
Configure HTTP memory-to-memory replication
...when we create 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.
Enable data replication among the application servers in a cluster
- Create a replication domain.
Using one of the following methods to create a replication domain:
- Create a replication domain manually.
Create manually without creating a new cluster...
Environment | Replication domains | New
We can specify the properties for the replication domain, including timeout, encryption, and number of replicas.
- Create a replication domain when we create a cluster.
To create a replication domain when we create a cluster, click...
Servers | Clusters | Clusters | New | Configure HTTP memory-to-memory replication
The replication domain 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 | New replication_domain_name
- 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 replication domain and dynamic cache uses a different replication domain. 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 application servers.
- (iSeries) Determine whether the configuration requires additional thread resources.
The replication service uses threads obtained from the DRS thread pool for various tasks, including processing messages. Previously, the replication service obtained threads from the default thread pool. When the application server starts up, the default maximum thread pool size for the DRS thread pool is 100 threads. However, this thread pool size might not be sufficient to enable 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, the number of replication consumers increases, or both.
Persistent data that is not being replicated to the application servers when the application server starts up might indicate needed to increase the setting for the maximum thread pool size. The maximum size of the DRS thread pool set to 100 is usually sufficient. However, in very large topologies, we might need to set the maximum thread pool size to a value that is greater than 100.
DRS thread pool custom properties
Property name Default value DRS_THREADPOOL_MINSIZE 40 DRS_THREADPOOL_MAXSIZE 100 DRS_THREADPOOL_ISGROWABLE false See documentation about Java virtual machine custom properties.
Data is replicating among the application servers in a configured replication domain.
What to do next
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, we should go to...
Environment | Replication domains | New page | Regenerate encryption key
After the key is regenerated, restart all of the application servers configured as part of the replication domain. Periodically regenerating the key improves data security.
Subtopics
- Data replication
- Replication domain collection
- Data replication domain settings
- Migrate servers from multi-broker replication domains to data replication domains
- Delete replication domains
- Replicating data with a multi-broker replication domain
Configure core group memory utilization Create clusters Configure cache replication Configure memory-to-memory replication for the peer-to-peer mode (default memory-to-memory replication) Enable or disable stateful session bean failover with the EJB container panel Replicating SIP sessions Data replication domain settings Thread pool settings Data replication domains Video: Creating a replication domain in WAS (V8.5.5)