Package org.apache.zookeeper.server.quorum

Class Learner

java.lang.Object

org.apache.zookeeper.server.quorum.Learner

Direct Known Subclasses:

Follower, Observer

public class Learner
extends java.lang.Object

This class is the superclass of two of the three main actors in a ZK ensemble: Followers and Observers. Both Followers and Observers share a good deal of code which is moved into Peer to avoid duplication.

Field Summary

Fields

Modifier and Type	Field	Description
protected java.io.BufferedOutputStream	bufferedOutput
protected org.apache.jute.InputArchive	leaderIs
protected org.apache.jute.OutputArchive	leaderOs
protected int	leaderProtocolVersion	the protocol version of the leader
protected static org.slf4j.Logger	LOG
protected java.net.Socket	sock

Constructor Summary

Constructors

Constructor	Description
Learner()

Method Summary

Modifier and Type	Method	Description
protected void	connectToLeader(java.net.InetSocketAddress addr, java.lang.String hostname)	Establish a connection with the Leader found by findLeader.
protected QuorumPeer.QuorumServer	findLeader()	Returns the address of the node we think is the leader.
int	getPendingRevalidationsCount()
java.net.Socket	getSocket()	Socket getter
protected void	ping(QuorumPacket qp)
protected long	registerWithLeader(int pktType)	Once connected to the leader, perform the handshake protocol to establish a following / observing connection.
protected void	revalidate(QuorumPacket qp)
void	shutdown()	Shutdown the Peer
protected void	syncWithLeader(long newLeaderZxid)	Finally, synchronize our history with the Leader.

Methods inherited from class java.lang.Object

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

Field Detail

bufferedOutput

protected java.io.BufferedOutputStream bufferedOutput

sock

protected java.net.Socket sock

leaderIs

protected org.apache.jute.InputArchive leaderIs

leaderOs

protected org.apache.jute.OutputArchive leaderOs

leaderProtocolVersion

protected int leaderProtocolVersion

the protocol version of the leader

LOG

protected static final org.slf4j.Logger LOG

Constructor Detail

Learner

public Learner()

Method Detail

getSocket

public java.net.Socket getSocket()

Socket getter

Returns:

getPendingRevalidationsCount

public int getPendingRevalidationsCount()

findLeader

protected QuorumPeer.QuorumServer findLeader()

Returns the address of the node we think is the leader.

connectToLeader

protected void connectToLeader(java.net.InetSocketAddress addr,
                               java.lang.String hostname)
                        throws java.io.IOException,
                               java.net.ConnectException,
                               java.lang.InterruptedException

Establish a connection with the Leader found by findLeader. Retries 5 times before giving up.

Parameters:

addr - - the address of the Leader to connect to.

Throws:

java.io.IOException -

if the socket connection fails on the 5th attempt

if there is an authentication failure while connecting to leader

java.net.ConnectException

java.lang.InterruptedException

registerWithLeader

protected long registerWithLeader(int pktType)
                           throws java.io.IOException

Once connected to the leader, perform the handshake protocol to establish a following / observing connection.

Parameters:

pktType -

Returns:

the zxid the Leader sends for synchronization purposes.

Throws:

java.io.IOException

syncWithLeader

protected void syncWithLeader(long newLeaderZxid)
                       throws java.io.IOException,
                              java.lang.InterruptedException

Finally, synchronize our history with the Leader.

Parameters:

newLeaderZxid -

Throws:

java.io.IOException

java.lang.InterruptedException

revalidate

protected void revalidate(QuorumPacket qp)
                   throws java.io.IOException

Throws:

java.io.IOException

ping

protected void ping(QuorumPacket qp)
             throws java.io.IOException

Throws:

java.io.IOException

shutdown

public void shutdown()

Shutdown the Peer