Package com.bigdata.quorum

This package defines interfaces and implementations for a quorum of highly available services.

See: Description

Interface Summary

Interface	Description
Quorum<S extends Remote,C extends QuorumClient<S>>	A quorum is a collection of services instances comprising the same logical service.
QuorumActor<S extends Remote,C extends QuorumClient<S>>	An interface that causes various changes in the distributed quorum state required to execute the intention of a QuorumMember service and its cognizant AbstractQuorum.
QuorumClient<S extends Remote>	A non-remote interface for a client which monitors the state of a quorum.
QuorumEvent	An interface for informational quorum events.
QuorumListener	An interface for receiving informational quorum events.
QuorumMember<S extends Remote>	A non-remote interface for a service which will participate in a quorum as a member service (as opposed to a client service that merely watches the quorum).
QuorumStateChangeEvent	Event data equivalent to the QuorumStateChangeListener API.
QuorumStateChangeListener	A non-remote interface containing only and all distributed quorum state change messages for this QuorumMember.
QuorumWatcher<S extends Remote,C extends QuorumClient<S>>	An interface that watches for changes in the distributed quorum state.
ServiceLookup<S extends Remote>

Class Summary

Class	Description
AbstractQuorum<S extends Remote,C extends QuorumClient<S>>	Abstract base class handles much of the logic for the distribution of RMI calls from the leader to the follower and for the HA write pipeline.
AbstractQuorum.E	Simple event impl.
AbstractQuorumClient<S extends Remote>	Base class for QuorumClients.
AbstractQuorumMember<S extends Remote>	Abstract base class for a QuorumMember.
AbstractQuorumTestCase	Abstract base class for testing using a MockQuorumFixture.
MockQuorumFixture	A mock object providing the shared quorum state for a set of QuorumClients running in the same JVM.
MockQuorumFixture.MockQuorum<S extends Remote,C extends QuorumMember<S>>	Mock Quorum implementation with increased visibility of some methods so we can pump state changes into the MockQuorumFixture2.
QCE	Event implementation class.
QuorumStateChangeListenerBase	QuorumStateChangeListener provides NOP method implementations.
QuorumTokenTransitions	Wraps the token/join transitions in a testable manner.
StressTestHA3	Stress test suite for TestHA3QuorumSemantics.
TestAll	Aggregates test suites in increasing dependency order.
TestHA3QuorumSemantics	Test the quorum semantics for a highly available quorum of 3 services.
TestMockQuorumFixture	Test suite for the MockQuorumFixture.
TestSingletonQuorumSemantics	Test the quorum semantics for a singleton quorum.

Enum Summary

Enum	Description
QuorumEventEnum	A type-safe enumeration for informational quorum events.
QuorumStateChangeEventEnum	Enumeration of event types for the events described by the QuorumStateChangeListener interface.

Exception Summary

Exception	Description
AsynchronousQuorumCloseException	An instance of this class is thrown when the caller is awaiting a quorum event and the quorum is asynchronously closed.
QuorumException	An exception related to Quorum or QuorumManagers.

Package com.bigdata.quorum Description

This package defines interfaces and implementations for a quorum of highly available services. Each quorum has a replication factor k, which must be an odd integer. A quorum with k := 1 is a singleton quorum and is not highly available. Highly available quorums have k := 3 or greater.

Persistent bigdata® services have a lastCommitTime in each root block. For the purpose of a highly available service, this timestamp provides a summary of the persistent state of the quorum. When (k+1)/2 services in the quorum vote for the same lastCommitTime, a simple majority exists and the quorum can meet. The quorum will elect a leader, which will assign a quorum token, and followers. Each quorum token is distinct. Applications can read and write on a quorum while it is met (all writes must be directed to the quorum leader). If the quorum breaks, then the token is cleared and operations will fail.

A quorum is inherently robust. Writes are replicated from the leader to the followers using a write pipeline so each service in the quorum has the same persistent state. If a service in a highly available quorum fails, the quorum will not break (unless the leader fails, in which case the quorum will meet again with the remaining services).