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 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

protected BufferedOutputStream	bufferedOutput
protected org.apache.jute.InputArchive	leaderIs
protected org.apache.jute.OutputArchive	leaderOs
protected static org.apache.log4j.Logger	LOG
protected Socket	sock

Constructor Summary

Learner()

Method Summary

protected void	connectToLeader(InetSocketAddress addr) Establish a connection with the Leader found by findLeader.
protected InetSocketAddress	findLeader() Returns the address of the node we think is the leader.
int	getPendingRevalidationsCount()
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 BufferedOutputStream bufferedOutput

sock

protected Socket sock

leaderIs

protected org.apache.jute.InputArchive leaderIs

leaderOs

protected org.apache.jute.OutputArchive leaderOs

LOG

protected static final org.apache.log4j.Logger LOG

Constructor Detail

Learner

public Learner()

Method Detail

getSocket

public Socket getSocket()

Socket getter

Returns:

getPendingRevalidationsCount

public int getPendingRevalidationsCount()

findLeader

protected InetSocketAddress findLeader()

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

connectToLeader

protected void connectToLeader(InetSocketAddress addr)
                        throws IOException,
                               ConnectException,
                               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:

IOException - - if the socket connection fails on the 5th attempt

ConnectException

InterruptedException

registerWithLeader

protected long registerWithLeader(int pktType)
                           throws 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:

IOException

syncWithLeader

protected void syncWithLeader(long newLeaderZxid)
                       throws IOException,
                              InterruptedException

Finally, synchronize our history with the Leader.

Parameters:

newLeaderZxid -

Throws:

IOException

InterruptedException

revalidate

protected void revalidate(QuorumPacket qp)
                   throws IOException

Throws:

IOException

ping

protected void ping(QuorumPacket qp)
             throws IOException

Throws:

IOException

shutdown

public void shutdown()

Shutdown the Peer