org.apache.zookeeper.server.quorum

Class LearnerSessionTracker

java.lang.Object

org.apache.zookeeper.server.quorum.UpgradeableSessionTracker

org.apache.zookeeper.server.quorum.LearnerSessionTracker

All Implemented Interfaces:

SessionTracker

public class LearnerSessionTracker
extends UpgradeableSessionTracker

The learner session tracker is used by learners (followers and observers) to track zookeeper sessions which may or may not be echoed to the leader. When a new session is created it is saved locally in a wrapped LocalSessionTracker. It can subsequently be upgraded to a global session as required. If an upgrade is requested the session is removed from local collections while keeping the same session ID. It is up to the caller to queue a session creation request for the leader. A secondary function of the learner session tracker is to remember sessions which have been touched in this service. This information is passed along to the leader with a ping.

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.zookeeper.server.SessionTracker

SessionTracker.Session, SessionTracker.SessionExpirer

Field Summary

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

localSessionsEnabled, localSessionTracker

Constructor Summary

Constructors

Constructor and Description
LearnerSessionTracker(SessionTracker.SessionExpirer expirer, ConcurrentMap<Long,Integer> sessionsWithTimeouts, int tickTime, long id, boolean localSessionsEnabled, ZooKeeperServerListener listener)

Method Summary

Modifier and Type	Method and Description
void	checkSession(long sessionId, Object owner) Checks whether the SessionTracker is aware of this session, the session is still active, and the owner matches.
boolean	commitSession(long sessionId, int sessionTimeout) Synchronized on this to avoid race condition of adding a local session after committed global session, which may cause the same session being tracked on this server and leader.
long	createSession(int sessionTimeout)
void	dumpSessions(PrintWriter pwriter) Text dump of session information, suitable for debugging.
Map<Long,Set<Long>>	getSessionExpiryMap() Returns a mapping of time to session IDs that expire at that time.
Set<Long>	globalSessions() Get a set of global session IDs
boolean	isGlobalSession(long sessionId)
void	removeSession(long sessionId)
void	setOwner(long sessionId, Object owner)
void	setSessionClosing(long sessionId) Mark that the session is in the process of closing.
void	shutdown()
Map<Long,Integer>	snapshot()
void	start()
boolean	touchSession(long sessionId, int sessionTimeout)
boolean	trackSession(long sessionId, int sessionTimeout) Track the session expire, not add to ZkDb.

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

checkGlobalSession, createLocalSessionTracker, finishedUpgrading, getLocalSessionCount, isLocalSession, isLocalSessionsEnabled, isTrackingSession, isUpgradingSession, localSessions, removeLocalSession, upgradeSession

Methods inherited from class java.lang.Object

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

Constructor Detail

LearnerSessionTracker

public LearnerSessionTracker(SessionTracker.SessionExpirer expirer,
                             ConcurrentMap<Long,Integer> sessionsWithTimeouts,
                             int tickTime,
                             long id,
                             boolean localSessionsEnabled,
                             ZooKeeperServerListener listener)

Method Detail

removeSession

public void removeSession(long sessionId)

start

public void start()

Overrides:

start in class UpgradeableSessionTracker

shutdown

public void shutdown()

isGlobalSession

public boolean isGlobalSession(long sessionId)

Specified by:

isGlobalSession in class UpgradeableSessionTracker

trackSession

public boolean trackSession(long sessionId,
                            int sessionTimeout)

Description copied from interface: SessionTracker

Track the session expire, not add to ZkDb.

Parameters:

sessionId - sessionId

sessionTimeout - sessionTimeout

Returns:

whether the session was newly tracked (if false, already tracked)

commitSession

public boolean commitSession(long sessionId,
                             int sessionTimeout)

Synchronized on this to avoid race condition of adding a local session after committed global session, which may cause the same session being tracked on this server and leader.

Parameters:

sessionId - sessionId

sessionTimeout - sessionTimeout

Returns:

whether the session was newly added (if false, already existed)

touchSession

public boolean touchSession(long sessionId,
                            int sessionTimeout)

Returns:

false if session is no longer active

snapshot

public Map<Long,Integer> snapshot()

createSession

public long createSession(int sessionTimeout)

checkSession

public void checkSession(long sessionId,
                         Object owner)
                  throws KeeperException.SessionExpiredException,
                         KeeperException.SessionMovedException

Description copied from interface: SessionTracker

Checks whether the SessionTracker is aware of this session, the session is still active, and the owner matches. If the owner wasn't previously set, this sets the owner of the session. UnknownSessionException should never been thrown to the client. It is only used internally to deal with possible local session from other machine

Throws:

KeeperException.SessionExpiredException

KeeperException.SessionMovedException

setOwner

public void setOwner(long sessionId,
                     Object owner)
              throws KeeperException.SessionExpiredException

Throws:

KeeperException.SessionExpiredException

dumpSessions

public void dumpSessions(PrintWriter pwriter)

Description copied from interface: SessionTracker

Text dump of session information, suitable for debugging.

Parameters:

pwriter - the output writer

setSessionClosing

public void setSessionClosing(long sessionId)

Description copied from interface: SessionTracker

Mark that the session is in the process of closing.

getSessionExpiryMap

public Map<Long,Set<Long>> getSessionExpiryMap()

Description copied from interface: SessionTracker

Returns a mapping of time to session IDs that expire at that time.

globalSessions

public Set<Long> globalSessions()

Description copied from interface: SessionTracker

Get a set of global session IDs