com.bigdata.quorum

Interface QuorumWatcher<S extends Remote,C extends QuorumClient<S>>

Type Parameters:

S -

C -

All Known Implementing Classes:

AbstractQuorum.QuorumWatcherBase, MockQuorumFixture.MockQuorum.MockQuorumWatcher

public interface QuorumWatcher<S extends Remote,C extends QuorumClient<S>>

An interface that watches for changes in the distributed quorum state. An implementation of this interface is generally an inner class of the concrete AbstractQuorum and is responsible for updating the internal state of the AbstractQuorum as it the distributed quorum state. The quorum internal state always reflects the distributed quorum state.

For example, the zookeeper implementation will watch the zpath whose children are the member services. If a new child appears, it will invoke AbstractQuorum#memberAdd(java.util.UUID) so the AbstractQuorum can update its internal state.

Since this interface watches the distributed state of the quorum, it does not have any specific methods which it must declare other than those which manage its life cycle (start/terminate). All of the interesting methods are on the AbstractQuorum class.

The QuorumWatcher is responsible for generating these events during its discovery phase when it starts running. The QuorumWatcher MUST report the discovered state in a manner consistent with the preconditions and postconditions defined for the QuorumActor the QuorumWatcher.

The QuorumActor provides the complementary functionality of causing changes in the distributed state of the quorum.

Author:

thompsonbry@users.sourceforge.net

See Also:

QuorumActor