com.bigdata.ha

Class QuorumCommitImpl<S extends HACommitGlue>

java.lang.Object

com.bigdata.quorum.QuorumStateChangeListenerBase

com.bigdata.ha.QuorumCommitImpl<S>

All Implemented Interfaces:

QuorumCommit<S>, QuorumStateChangeListener, ServiceLookup<HACommitGlue>

public class QuorumCommitImpl<S extends HACommitGlue>
extends QuorumStateChangeListenerBase
implements QuorumCommit<S>, QuorumStateChangeListener, ServiceLookup<HACommitGlue>

QuorumCommit implementation.

Constructor Summary

Constructors

Constructor and Description
QuorumCommitImpl(QuorumMember<S> member)

Method Summary

Methods

Modifier and Type	Method and Description
void	abort2Phase(long token) Used by the leader to send a message to each service joined with the quorum telling it to discard its write set, reloading all state from the last root block.
CommitResponse	commit2Phase(CommitRequest commitRequest) Used by the leader to send a message to each joined service in the quorum telling it to commit using the root block from the corresponding prepare message.
HACommitGlue	getService(UUID serviceId) Return the remote interface used to perform HA operations on a member of quorum.
PrepareResponse	prepare2Phase(PrepareRequest req) Used by the leader to send a message to each joined service in the quorum instructing it to flush all writes to the backing channel, and acknowledge "yes" if ready to commit.

Methods inherited from class com.bigdata.quorum.QuorumStateChangeListenerBase

consensus, lostConsensus, memberAdd, memberRemove, pipelineAdd, pipelineChange, pipelineElectedLeader, pipelineRemove, pipelineUpstreamChange, quorumBreak, quorumMeet, serviceJoin, serviceLeave

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.bigdata.quorum.QuorumStateChangeListener

consensus, lostConsensus, memberAdd, memberRemove, pipelineAdd, pipelineChange, pipelineElectedLeader, pipelineRemove, pipelineUpstreamChange, quorumBreak, quorumMeet, serviceJoin, serviceLeave

Constructor Detail

QuorumCommitImpl

public QuorumCommitImpl(QuorumMember<S> member)

Method Detail

getService

public HACommitGlue getService(UUID serviceId)

Description copied from interface: ServiceLookup

Return the remote interface used to perform HA operations on a member of quorum.

Specified by:

getService in interface ServiceLookup<HACommitGlue>

Parameters:

serviceId - The UUID associated with the service.

Returns:

The remote interface for that quorum member.

prepare2Phase

public PrepareResponse prepare2Phase(PrepareRequest req)
                              throws InterruptedException,
                                     IOException

Used by the leader to send a message to each joined service in the quorum instructing it to flush all writes to the backing channel, and acknowledge "yes" if ready to commit. If the service can not prepare for any reason, then it must return "no". The service must save a copy of the root block for use with the next commit message.

This implementation runs the operation on the leader in the caller's thread to avoid deadlock. The other services run the operation asynchronously on their side while the leader awaits their future's using get().

Note: The IHA2PhasePrepareMessage is sent to all services in write pipeline. This ensures that services that are not yet joined with the met quorum will still observe the root blocks. This is necessary in order for them to catch up with the met quorum. The 2-phase commit protocol is "aware" that not all messages are being sent to services whose votes count. Only services that are actually in the met quorum get a vote.

Note: This method is responsible for the atomic decision regarding whether a service will be considered to be "joined" with the met quorum for the 2-phase commit. A service that is synchronizing will either have already voted the appropriate lastCommitTime and entered the met quorum or it will not. That decision point is captured atomically when we obtain a snapshot of the joined services from the quorum state. The decision is propagated through the IHA2PhasePrepareMessage and that information is retained by the service together with the new root block from the prepare message. This metadata is used to decide how the service will handle the prepare, commit, and abort messages.

Specified by:

prepare2Phase in interface QuorumCommit<S extends HACommitGlue>

Returns:

The outcome of the distributed PREPARE request, indicating whether each service is prepared to commit.

Throws:

InterruptedException

IOException

commit2Phase

public CommitResponse commit2Phase(CommitRequest commitRequest)
                            throws IOException,
                                   InterruptedException

Description copied from interface: QuorumCommit

Used by the leader to send a message to each joined service in the quorum telling it to commit using the root block from the corresponding prepare message. The commit MAY NOT go forward unless both the current quorum token and the lastCommitTime on this message agree with the quorum token and lastCommitTime in the root block from the last "prepare" message.

Specified by:

commit2Phase in interface QuorumCommit<S extends HACommitGlue>

Throws:

IOException

InterruptedException

abort2Phase

public void abort2Phase(long token)
                 throws IOException,
                        InterruptedException

Used by the leader to send a message to each service joined with the quorum telling it to discard its write set, reloading all state from the last root block. If the node has not observed the corresponding "prepare" message then it should ignore this message. FIXME Only issue abort to services that voted YES in prepare? [We have that information in commitNow(), but we do not have the atomic set of joined services in AbstractJournal.abort())].

Specified by:

abort2Phase in interface QuorumCommit<S extends HACommitGlue>

Parameters:

token - The quorum token.

Throws:

IOException

InterruptedException