org.apache.zookeeper.server.quorum

Class Leader

java.lang.Object

org.apache.zookeeper.server.quorum.Leader

public class Leader
extends Object

This class has the control logic for the Leader.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	Leader.Proposal
static class	Leader.XidRolloverException

Field Summary

Fields

Modifier and Type	Field and Description
static int	ACKEPOCH This message is used by the follow to ack a proposed epoch.
protected Set<Long>	connectingFollowers
protected Set<Long>	electingFollowers
protected boolean	electionFinished
static int	LEADERINFO This message is the first that a follower receives from the leader.
protected Leader.Proposal	newLeaderProposal
static int	PROPOSAL This message type is sent by a leader to propose a mutation.
protected boolean	quorumFormed

Method Summary

Modifier and Type	Method and Description
void	commit(long zxid) Create a commit packet and send it to all the members of the quorum
void	commitAndActivate(long zxid, long designatedLeader)
LearnerSnapshotThrottler	createLearnerSnapshotThrottler(int maxConcurrentSnapshots, long maxConcurrentSnapshotTimeout)
long	getEpoch() Returns the current epoch of the leader.
long	getEpochToPropose(long sid, long lastAcceptedEpoch)
List<LearnerHandler>	getForwardingFollowers() Returns a copy of the current forwarding follower snapshot
List<LearnerHandler>	getLearners() Returns a copy of the current learner snapshot
LearnerSnapshotThrottler	getLearnerSnapshotThrottler()
int	getNumPendingSyncs()
List<LearnerHandler>	getObservingLearners() Returns a copy of the current observer snapshot
static String	getPacketType(int packetType) Get string representation of a given packet type
BufferStats	getProposalStats()
void	inform(Leader.Proposal proposal) Create an inform packet and send it to all observers.
void	informAndActivate(Leader.Proposal proposal, long designatedLeader) Create an inform&activate packet and send it to all observers.
boolean	isQuorumSynced(QuorumVerifier qv) Returns true if a quorum in qv is connected and synced with the leader and false otherwise
void	processAck(long sid, long zxid, SocketAddress followerAddr) Keep a count of acks that are received by the leader for a particular proposal
void	processSync(LearnerSyncRequest r) Process sync requests
Leader.Proposal	propose(Request request) create a proposal and send it out to all the members
void	sendSync(LearnerSyncRequest r) Sends a sync message to the appropriate server
long	startForwarding(LearnerHandler handler, long lastSeenZxid) lets the leader know that a follower is capable of following and is done syncing
boolean	tryToCommit(Leader.Proposal p, long zxid, SocketAddress followerAddr)
void	waitForEpochAck(long id, StateSummary ss)
void	waitForNewLeaderAck(long sid, long zxid) Process NEWLEADER ack of a given sid and wait until the leader receives sufficient acks.

Methods inherited from class java.lang.Object

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

Field Detail

quorumFormed

protected boolean quorumFormed

LEADERINFO

public static final int LEADERINFO

This message is the first that a follower receives from the leader. It has the protocol version and the epoch of the leader.

See Also:

Constant Field Values

ACKEPOCH

public static final int ACKEPOCH

This message is used by the follow to ack a proposed epoch.

See Also:

Constant Field Values

PROPOSAL

public static final int PROPOSAL

This message type is sent by a leader to propose a mutation.

See Also:

Constant Field Values

newLeaderProposal

protected final Leader.Proposal newLeaderProposal

connectingFollowers

protected final Set<Long> connectingFollowers

electingFollowers

protected final Set<Long> electingFollowers

electionFinished

protected boolean electionFinished

Method Detail

getProposalStats

public BufferStats getProposalStats()

createLearnerSnapshotThrottler

public LearnerSnapshotThrottler createLearnerSnapshotThrottler(int maxConcurrentSnapshots,
                                                               long maxConcurrentSnapshotTimeout)

getLearners

public List<LearnerHandler> getLearners()

Returns a copy of the current learner snapshot

getForwardingFollowers

public List<LearnerHandler> getForwardingFollowers()

Returns a copy of the current forwarding follower snapshot

getObservingLearners

public List<LearnerHandler> getObservingLearners()

Returns a copy of the current observer snapshot

getNumPendingSyncs

public int getNumPendingSyncs()

isQuorumSynced

public boolean isQuorumSynced(QuorumVerifier qv)

Returns true if a quorum in qv is connected and synced with the leader and false otherwise

Parameters:

qv, - a QuorumVerifier

tryToCommit

public boolean tryToCommit(Leader.Proposal p,
                           long zxid,
                           SocketAddress followerAddr)

Returns:

True if committed, otherwise false.

processAck

public void processAck(long sid,
                       long zxid,
                       SocketAddress followerAddr)

Keep a count of acks that are received by the leader for a particular proposal

Parameters:

zxid, - the zxid of the proposal sent out

sid, - the id of the server that sent the ack

followerAddr -

commit

public void commit(long zxid)

Create a commit packet and send it to all the members of the quorum

Parameters:

zxid -

commitAndActivate

public void commitAndActivate(long zxid,
                              long designatedLeader)

inform

public void inform(Leader.Proposal proposal)

Create an inform packet and send it to all observers.

informAndActivate

public void informAndActivate(Leader.Proposal proposal,
                              long designatedLeader)

Create an inform&activate packet and send it to all observers.

getEpoch

public long getEpoch()

Returns the current epoch of the leader.

Returns:

propose

public Leader.Proposal propose(Request request)
                        throws Leader.XidRolloverException

create a proposal and send it out to all the members

Parameters:

request -

Returns:

the proposal that is queued to send to all the members

Throws:

Leader.XidRolloverException

getLearnerSnapshotThrottler

public LearnerSnapshotThrottler getLearnerSnapshotThrottler()

processSync

public void processSync(LearnerSyncRequest r)

Process sync requests

Parameters:

r - the request

sendSync

public void sendSync(LearnerSyncRequest r)

Sends a sync message to the appropriate server

startForwarding

public long startForwarding(LearnerHandler handler,
                            long lastSeenZxid)

lets the leader know that a follower is capable of following and is done syncing

Parameters:

handler - handler of the follower

Returns:

last proposed zxid

Throws:

InterruptedException

getEpochToPropose

public long getEpochToPropose(long sid,
                              long lastAcceptedEpoch)
                       throws InterruptedException,
                              IOException

Throws:

InterruptedException

IOException

waitForEpochAck

public void waitForEpochAck(long id,
                            StateSummary ss)
                     throws IOException,
                            InterruptedException

Throws:

IOException

InterruptedException

waitForNewLeaderAck

public void waitForNewLeaderAck(long sid,
                                long zxid)
                         throws InterruptedException

Process NEWLEADER ack of a given sid and wait until the leader receives sufficient acks.

Parameters:

sid -

Throws:

InterruptedException

getPacketType

public static String getPacketType(int packetType)

Get string representation of a given packet type

Parameters:

packetType -

Returns:

string representing the packet type