/**
* Registers the monitor with the group so that it can be kept informed about the outcome of
* elections and group membership changes. The monitor, just like a replication node, is
* identified by its nodeName. The Monitor uses the helper nodes to locate a master with which it
* can register itself. If the helper nodes are not available the registration will fail.
*
* <p>A monitor must be registered at least once, if it needs to be kept up to date about ongoing
* election results and group changes. Attempts to re-register the same monitor are ignored.
* Registration, once it has been completed successfully persists beyond the lifetime of the
* Monitor instance and does not need to be repeated. Repeated registrations are benign and merely
* confirm that the current monitor configuration is consistent with earlier registrations of this
* monitor.
*
* @return the node that is the current master
* @throws EnvironmentFailureException if an unexpected, internal or environment-wide failure
* occurs.
* @throws IllegalStateException if the monitor has been shutdown, or no helper sockets were
* specified at Monitor initialization.
*/
public ReplicationNode register() throws EnvironmentFailureException {
if (shutdown.get()) {
throw new IllegalStateException("The monitor has been shutdown");
}
if (repGroupAdmin.getHelperSockets().size() == 0) {
throw new IllegalStateException("No helper sockets were specified at Monitor initialization");
}
RepNodeImpl monitorNode =
new RepNodeImpl(
nameIdPair,
NodeType.MONITOR,
monitorConfig.getNodeHostname(),
monitorConfig.getNodePort());
/* Ensure that the monitor is part of the group. */
return repGroupAdmin.ensureMonitor(monitorNode);
}
