The remote event notification framework allows a subset of the information available through Kodo's transaction events (see Section 9.8, “Transaction Events”) to be broadcast to remote listeners. Kodo's data cache, for example, uses remote events to remain synchronized when deployed in multiple JVMs.
![[Important]](img/important.gif) | Important |
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This feature requires Kodo Enterprise Edition or Kodo Standard Edition with the Performance Pack. |
To enable remote events, you must configure the
EntityManagerFactory or PersistenceManagerFactory
to use a RemoteCommitProvider (see below).
When a RemoteCommitProvider is properly configured, you
can register
RemoteCommitListeners that will be alerted
with a list of modified object ids whenever a transaction on a remote
machine successfully commits.
Kodo includes built in remote commit providers for JMS and TCP communication.
Kodo includes built in remote commit providers for JMS and TCP
communication. The JMS remote commit provider can be configured by
setting the
kodo.RemoteCommitProvider property
to contain the appropriate configuration properties. The JMS
provider understands the following properties:
Topic: The topic that the remote commit provider should publish notifications to and subscribe to for notifications sent from other JVMs. Defaults totopic/KodoCommitProviderTopicTopicConnectionFactory: The JNDI name of ajavax.jms.TopicConnectionFactoryfactory to use for finding topics. Defaults tojava:/ConnectionFactory. This setting may vary depending on the application server in use; consult the application server's documentation for details of the default JNDI name for thejavax.jms.TopicConnectionFactoryinstance. For example, under Weblogic, the JNDI name for the TopicConnectionFactory isjavax.jms.TopicConnectionFactory.ExceptionReconnectAttempts: The number of times to attempt to reconnect if the JMS system notifies Kodo of a serious connection error. Defaults to 0, meaning Kodo will log the error but otherwise ignore it, hoping the connection is still valid.*: All other configuration properties will be interpreted as settings to pass to the JNDIInitialContexton construction. For example, you might set thejava.naming.provider.urlproperty to the URL of the context provider.
To configure a factory to use the JMS provider, your properties might look like the following:
Example 11.8. JMS Remote Commit Provider Configuration
JPA XML format:
<property name="kodo.RemoteCommitProvider" value="jms(Topic=topic/KodoCommitProviderTopic)"/>
JDO properties format:
kodo.RemoteCommitProvider: jms(Topic=topic/KodoCommitProviderTopic)
![[Note]](img/note.gif) | Note |
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Because of the nature of JMS, it is important that you invoke
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The TCP remote commit provider has several options that are
defined as host specifications containing a host name or IP
address and an optional port separated by a colon. For example,
the host specification saturn.bea.com:1234
represents an InetAddress retrieved by
invoking InetAddress.getByName ("saturn.bea.com")
and a port of 1234.
The TCP provider can be configured by setting the
kodo.RemoteCommitProvider plugin property to contain the
appropriate configuration settings. The TCP provider understands the
following properties:
Port: The TCP port that the provider should listen on for commit notifications. Defaults to 5636.Addresses: A semicolon-separated list of IP addresses to which notifications should be sent. No default value.NumBroadcastThreads: The number of threads to create for the purpose of transmitting events to peers. You sould increase this value as the number of concurrent transactions increases. The maximum number of concurrent transactions is a function of the size of the connection pool. See the theMaxActiveproperty ofkodo.ConnectionFactoryPropertiesin Section 4.1, “Using the Kodo DataSource”. Setting a value of 0 will result in behavior where the thread invokingcommitwill perform the broadcast directly. Defaults to 2.RecoveryTimeMillis: Amount of time to wait in milliseconds before attempting to reconnect to a peer of the cluster when connectivity to the peer is lost. Defaults to 15000.MaxIdle: The number of TCP sockets (channels) to keep open to each peer in the cluster for the transmission of events. Defaults to 2.MaxActive: The maximum allowed number of TCP sockets (channels) to open simultaneously between each peer in the cluster. Defaults to 2.
To configure a factory to use the TCP provider, your properties might look like the following:
In addition to the provider-specific configuration options above, all providers accept the following plugin properties:
TransmitPersistedObjectIds: Whether remote commit events will include the object ids of instances persisted in the transaction. By default only the class names of types persisted in the transaction are sent. This results in smaller events and more efficient network utilization. If you have registered your own remote commit listeners, however, you may require the persisted object ids as well.
To transmit persisted object ids in our remote commit events using the JMS provider, we modify the previous example as follows:
Example 11.10. Transmitting Persisted Object Ids
JPA XML format:
<property name="kodo.RemoteCommitProvider"
value="jms(Topic=topic/KodoCommitProviderTopic, TransmitPersistedObjectIds=true)"/>
JDO properties format:
kodo.RemoteCommitProvider: jms(Topic=topic/KodoCommitProviderTopic, TransmitPersistedObjectIds=true)
You can develop additional mechanisms for remote event notification be
by creating an implementation of the
RemoteCommitProvider interface, possibly by
extending the
AbstractRemoteCommitProvider
abstract class. For details on particular customization needs,
contact us at
support@solarmetric.com.
