com.bigdata.ha

Interface QuorumService<S extends HAGlue>

All Superinterfaces:

QuorumClient<S>, QuorumCommit<S>, QuorumListener, QuorumMember<S>, QuorumPipeline<S>, QuorumRead<S>, QuorumStateChangeListener, ServiceLookup<S>

All Known Implementing Classes:

QuorumServiceBase

public interface QuorumService<S extends HAGlue>
extends QuorumMember<S>, QuorumRead<S>, QuorumCommit<S>, QuorumPipeline<S>

A non-remote interface for a member service in a Quorum defining methods to support service specific high availability operations such as reading on another member of the quorum, the 2-phase quorum commit protocol, replicating writes, etc.

A QuorumService participates in a write pipeline, which replicates cache blocks from the leader and relays them from service to service in the pipeline order. The write pipeline is responsible for ensuring that the followers will have the same persistent state as the leader at each commit point. Services which are synchronizing may also join the write pipeline in order to receive updates before they join a met quorum. See QuorumPipeline.

The leader uses a 2-phase commit protocol to ensure that the quorum enters each commit point atomically and that followers can read historical commit points, including on the prior commit point. See QuorumCommit.

Persistent services use pre-record checksums to detect read errors and can handle read failures by reading on another service joined with the quorum. See QuorumRead.

Version:

$Id$

Author:

Bryan Thompson

Method Summary

Methods

Modifier and Type	Method and Description
void	discardWriteSet() Discard all state associated with the current write set.
void	enterErrorState() Enter an error state.
long	getLastCommitCounter() Return the lastCommitCounter for this service (based on its current root block).
long	getLastCommitTime() Return the lastCommitTime for this service (based on its current root block).
int	getPID() Return the best guess at the process identifier for this process.
long	getPrepareTimeout() Return the configured timeout in milliseconds that the leader will await the other services to prepare for a 2-phase commit.
File	getServiceDir() Return the service directory.
void	installRootBlocks(IRootBlockView rootBlock0, IRootBlockView rootBlock1) Install root blocks on the local service.

Methods inherited from interface com.bigdata.quorum.QuorumMember

assertLeader, getActor, getDownstreamServiceId, getExecutor, getService, getServiceId, isFollower, isJoinedMember, isLastInChain, isLeader, isMember, isPipelineMember

Methods inherited from interface com.bigdata.quorum.QuorumClient

disconnected, getLeader, getLogicalServiceZPath, getQuorum, getService, start, terminate

Methods inherited from interface com.bigdata.quorum.QuorumListener

notify

Methods inherited from interface com.bigdata.quorum.QuorumStateChangeListener

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

Methods inherited from interface com.bigdata.ha.QuorumRead

readFromQuorum

Methods inherited from interface com.bigdata.ha.QuorumCommit

abort2Phase, commit2Phase, prepare2Phase

Methods inherited from interface com.bigdata.ha.QuorumPipeline

getStoreUUID, logRootBlock, logWriteCacheBlock, purgeHALogs, receiveAndReplicate, replicate, resetPipeline

Method Detail

getLastCommitTime

long getLastCommitTime()

Return the lastCommitTime for this service (based on its current root block).

Specified by:

getLastCommitTime in interface QuorumPipeline<S extends HAGlue>

getLastCommitCounter

long getLastCommitCounter()

Return the lastCommitCounter for this service (based on its current root block).

Specified by:

getLastCommitCounter in interface QuorumPipeline<S extends HAGlue>

getServiceDir

File getServiceDir()

Return the service directory. This directory has various metadata about the service process, but it might not contain either the data or the HA log files.

getPID

int getPID()

Return the best guess at the process identifier for this process.

getPrepareTimeout

long getPrepareTimeout()

Return the configured timeout in milliseconds that the leader will await the other services to prepare for a 2-phase commit.

installRootBlocks

void installRootBlocks(IRootBlockView rootBlock0,
                     IRootBlockView rootBlock1)

Install root blocks on the local service. This is used for a few different conditions in HA.

1. When the quorum meets for the first time, we need to take the root block from the leader and use it to replace both of our root blocks (the initial root blocks are identical). That will make the root blocks the same on all quorum members.
2. REBUILD: When a service goes through an automated disaster recovery, we need to install new root blocks in order to make the local journal logically empty. This prevents the service from attempting to interpret the data on the backing file if there is a restart part way through the rebuild operation.

Note: The initial root blocks on a service are identical, so this root block will be installed as both root block ZERO (0) and root block ONE (1).

Parameters:

rootBlock0 - Root block ZERO (0).

rootBlock1 - Root block ONE (1).

enterErrorState

void enterErrorState()

Enter an error state. The error state should take whatever corrective actions are necessary in order to prepare the service for continued operations.

discardWriteSet

void discardWriteSet()

Discard all state associated with the current write set.