This saves application developers significant amounts of time, and allows for the application to be deployed in different environments, without having to change code. Flexible Protocol Stack. About this Website. Hosted by. In a JGroups cluster, all nodes have to store all messages received for potential retransmission in case of a failure.
However, if we store all messages forever, we will run out of memory. So, the distributed garbage collection service in JGroups periodically purges messages that have seen by all nodes from the memory in each node. The distributed garbage collection service is configured in the pbcast. Value 0 disables this service. After this number is reached, there is no garbage collection until the message is received.
When a network error occurs, the cluster might be partitioned into several different partitions. JGroups has a MERGE service that allows the coordinators in partitions to communicate with each other and form a single cluster back again. JBoss Cache provides distributed cache and state replication services for the JBoss cluster. A generic TreeCache MBean configuration is listed below. Application specific TreeCache MBean configurations are covered in later chapters when those applications are discussed.
The JGroups configuration element i. You have learned how to configure JGroups earlier in this chapter Section The TreeCache MBean takes the following attributes. CacheLoaderClass specifies the fully qualified class name of the CacheLoader implementation.
CacheLoaderConfig contains a set of properties from which the specific CacheLoader implementation can configure itself. CacheLoaderFetchPersistentState specifies whether to fetch the persistent state from another node. The persistence is fetched only if CacheLoaderShared is false. This attribute is only used if FetchStateOnStartup is true. CacheLoaderFetchTransientState specifies whether to fetch the in-memory state from another node. CacheLoaderPreload contains a list of comma-separate nodes that need to be preloaded e.
CacheLoaderShared specifies whether we want to shared a datastore, or whether each node wants to have its own local datastore. CacheMode specifies how to synchronize cache between nodes. ClusterName specifies the name of the cluster. This value needs to be the same for all nodes in a cluster in order for them to find each other.
ClusterConfig contains the configuration of the underlying JGroups stack see Section EvictionPolicyClass specifies the name of a class implementing EvictionPolicy. If this attribute is empty, no eviction policy is enabled. EvictionPolicyConfig contains the configuration parameter for the specified eviction policy.
Note that the content is provider specific. FetchStateOnStartup specifies whether or not to acquire the initial state from existing members. InitialStateRetrievalTimeout specifies the time in milliseconds to wait for initial state retrieval. IsolationLevel specifies the node locking level. LockAcquisitionTimeout specifies the time in milliseconds to wait for a lock to be acquired. If a lock cannot be acquired an exception will be thrown.
ReplQueueInterval specifies the time in milliseconds for elements from the replication queue to be replicated. SyncReplTimeout specifies the time in milliseconds to wait until replication ACKs have been received from all nodes in the cluster.
This attribute applies to synchronous replication mode only i. ReplQueueMaxElements specifies the maximum number of elements in the replication queue until replication kicks in.
There is also an option of DummyTransactionManagerLookup for simple standalone examples. Chapter JGroups Configuration. Transport Protocols. UDP configuration. Note On Windows machines, because of the media sense feature being broken with multicast even after disabling media sense , you need to set the UDP protocol's loopback attribute to true.
TCP configuration. Discovery Protocols. Failure Detection Protocols. Note Regular traffic from a node counts as if it is a live. Reliable Delivery Protocols. Other Configuration Options. Group Membership. Flow Control.
The jgroups subsystem uses its own thread pools for processing cluster communication. JGroups contains thread pools for default , internal , oob , and timer functions which you can configure individually. Each JGroups thread pool includes configurable attributes for keepalive-time , max-threads , min-threads , and queue-length. Appropriate values for each thread pool attribute depend on your environment, but for most situations the default values should suffice.
Appropriate values for JGroups buffers depend on your environment, but for most situations the default values should suffice. It is recommended that you test your cluster under load in a development environment to tune appropriate values for the buffer sizes. Your operating system may limit the available buffer sizes and JBoss EAP may not be able to use its configured buffer values.
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