org.apache.zookeeper.server.quorum

Class Observer

java.lang.Object

org.apache.zookeeper.server.quorum.Learner

org.apache.zookeeper.server.quorum.Observer

public class Observer
extends Learner

Observers are peers that do not take part in the atomic broadcast protocol. Instead, they are informed of successful proposals by the Leader. Observers therefore naturally act as a relay point for publishing the proposal stream and can relieve Followers of some of the connection load. Observers may submit proposals, but do not vote in their acceptance. See ZOOKEEPER-368 for a discussion of this feature.

Field Summary

Fields

Modifier and Type	Field and Description
static String	OBSERVER_ELECTION_DELAY_MS Delay the Observer's participation in a leader election upon disconnect so as to prevent unexpected additional load on the voting peers during the process.
static String	OBSERVER_RECONNECT_DELAY_MS When observer lost its connection with the leader, it waits for 0 to the specified value before trying to reconnect with the leader.

Fields inherited from class org.apache.zookeeper.server.quorum.Learner

bufferedOutput, leaderAddr, leaderIs, leaderOs, leaderProtocolVersion, messageTracker, sock

Method Summary

Modifier and Type	Method and Description
QuorumPeer.QuorumServer	getCurrentLearnerMaster()
long	getLearnerMasterId()
static long	getObserverElectionDelayMs()
protected void	processPacket(QuorumPacket qp) Controls the response of an observer to the receipt of a quorumpacket
boolean	setLearnerMaster(String learnerMaster) Prompts the Observer to disconnect from its current learner master and reconnect to the specified server.
static void	setObserverElectionDelayMs(long electionDelayMs)
void	shutdown() Shutdown the Observer.
String	toString()

Methods inherited from class org.apache.zookeeper.server.quorum.Learner

connectToLeader, createSocket, findLeader, getPendingRevalidationsCount, getSocket, nanoTime, ping, registerWithLeader, revalidate, sockConnect, syncWithLeader

Methods inherited from class java.lang.Object

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

Field Detail

OBSERVER_RECONNECT_DELAY_MS

public static final String OBSERVER_RECONNECT_DELAY_MS

When observer lost its connection with the leader, it waits for 0 to the specified value before trying to reconnect with the leader. So that the entire observer fleet won't try to run leader election and reconnect to the leader at once. Default value is zero.

See Also:

Constant Field Values

OBSERVER_ELECTION_DELAY_MS

public static final String OBSERVER_ELECTION_DELAY_MS

Delay the Observer's participation in a leader election upon disconnect so as to prevent unexpected additional load on the voting peers during the process. Default value is 200.

See Also:

Constant Field Values

Method Detail

toString

public String toString()

Overrides:

toString in class Object

processPacket

protected void processPacket(QuorumPacket qp)
                      throws Exception

Controls the response of an observer to the receipt of a quorumpacket

Parameters:

qp -

Throws:

Exception

shutdown

public void shutdown()

Shutdown the Observer.

Overrides:

shutdown in class Learner

getLearnerMasterId

public long getLearnerMasterId()

setLearnerMaster

public boolean setLearnerMaster(String learnerMaster)

Prompts the Observer to disconnect from its current learner master and reconnect to the specified server. If that connection attempt fails, the Observer will fail over to the next available learner master.

getCurrentLearnerMaster

public QuorumPeer.QuorumServer getCurrentLearnerMaster()

getObserverElectionDelayMs

public static long getObserverElectionDelayMs()

setObserverElectionDelayMs

public static void setObserverElectionDelayMs(long electionDelayMs)