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.
To enable remote events, you must configure the
to use a
RemoteCommitProvider (see below).
RemoteCommitProvider is properly configured, you
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
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 to
TopicConnectionFactory: The JNDI name of
factory to use for finding topics. Defaults to
java:/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 the
instance. For example, under Weblogic, the JNDI name
for the TopicConnectionFactory is
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 JNDI
InitialContext on construction. For
example, you might set the
property to the URL of the context provider.
To configure a factory to use the JMS provider, your properties might look like the following:
Example 11.9. JMS Remote Commit Provider Configuration
JPA XML format:
<property name="kodo.RemoteCommitProvider" value="jms(Topic=topic/KodoCommitProviderTopic)"/>
JDO properties format:
Because of the nature of JMS, it is important that you invoke
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
InetAddress retrieved by
and a port of 1234.
Port: The TCP port that the provider
should listen on for commit notifications. Defaults to
Addresses: A semicolon-separated list of
IP addresses to which notifications should be sent. No
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 the
Section 4.1, “Using the Kodo DataSource”.
Setting a value of 0 will result in behavior where the
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:
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 11.11. 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)