org.apache.catalina.cluster.session
Class SimpleTcpReplicationManager

java.lang.Object
  org.apache.catalina.session.ManagerBase
      org.apache.catalina.session.StandardManager
          org.apache.catalina.cluster.session.SimpleTcpReplicationManager

All Implemented Interfaces:

ClusterManager, java.util.EventListener, Lifecycle, Manager, javax.management.MBeanRegistration, java.beans.PropertyChangeListener

public class SimpleTcpReplicationManager

extends StandardManager

implements ClusterManager

Title: Tomcat Session Replication for Tomcat 4.0
Description: A very simple straight forward implementation of session replication of servers in a cluster.
This session replication is implemented "live". By live I mean, when a session attribute is added into a session on Node A a message is broadcasted to other messages and setAttribute is called on the replicated sessions.
A full description of this implementation can be found under Filip's Tomcat Page
Copyright: See apache license Company: www.filip.net

Version:

1.0 for TC 4.0 Description: The InMemoryReplicationManager is a session manager that replicated session information in memory. It uses JavaGroups as a communication protocol to ensure guaranteed and ordered message delivery. JavaGroups also provides a very flexible protocol stack to ensure that the replication can be used in any environment.

The InMemoryReplicationManager extends the StandardManager hence it allows for us to inherit all the basic session management features like expiration, session listeners etc

To communicate with other nodes in the cluster, the InMemoryReplicationManager sends out 7 different type of multicast messages all defined in the SessionMessage class.
When a session is replicated (not an attribute added/removed) the session is serialized into a byte array using the StandardSession.readObjectData, StandardSession.writeObjectData methods.

Author:

Filip Hanik, Bela Ban (modifications for synchronous replication)

Field Summary

protected CatalinaCluster	cluster
protected boolean	defaultMode
protected boolean	distributable
protected java.util.HashMap	invalidatedSessions
static org.apache.commons.logging.Log	log
protected java.lang.String	mChannelConfig
protected boolean	mChannelStarted
protected boolean	mExpireSessionsOnShutdown Set to true if we don't want the sessions to expire on shutdown
protected java.lang.String	mGroupName
protected boolean	mManagerRunning
protected boolean	mPrintToScreen
protected java.lang.String	name
protected boolean	stateTransferred Flag to keep track if the state has been transferred or not Assumes false.
protected boolean	synchronousReplication Use synchronous rather than asynchronous replication.
protected boolean	useDirtyFlag

Fields inherited from class org.apache.catalina.session.StandardManager

info, lifecycle, maxActiveSessions, pathname, processingTime, rejectedSessions, started

Fields inherited from class org.apache.catalina.session.ManagerBase

algorithm, container, DEFAULT_ALGORITHM, devRandomSource, digest, domain, duplicates, entropy, expiredSessions, initialized, maxActive, maxInactiveInterval, mserver, oname, processExpiresFrequency, random, randomClass, randomIS, sessionAverageAliveTime, sessionCounter, sessionIdLength, sessionMaxAliveTime, sessions, sm, support

Fields inherited from interface org.apache.catalina.Lifecycle

AFTER_START_EVENT, AFTER_STOP_EVENT, BEFORE_START_EVENT, BEFORE_STOP_EVENT, DESTROY_EVENT, INIT_EVENT, PERIODIC_EVENT, START_EVENT, STOP_EVENT

Constructor Summary

SimpleTcpReplicationManager()
Constructor, just calls super()

Method Summary

Session	createSession(java.lang.String sessionId) Construct and return a new session object, based on the default settings specified by this Manager's properties.
protected Session	createSession(java.lang.String sessionId, boolean notify, boolean setId) Creates a HTTP session.
CatalinaCluster	getCluster()
boolean	getDistributable() Return the distributable flag for the sessions supported by this Manager.
boolean	getExpireSessionsOnShutdown()
java.lang.String[]	getInvalidatedSessions() When the manager expires session not tied to a request.
java.lang.String	getName() Return the name of the manager, at host /context name and at engine hostname+/context.
boolean	isDefaultMode()
boolean	isManagerRunning()
boolean	isNotifyListenersOnReplication()
boolean	isSendClusterDomainOnly()
boolean	isStateTransferred()
void	messageDataReceived(ClusterMessage cmsg) A message was received from another node, this is the callback method to implement if you are interested in receiving replication messages.
protected void	messageReceived(SessionMessage msg, Member sender) This method is called by the received thread when a SessionMessage has been received from one of the other nodes in the cluster.
protected Session	readSession(byte[] data, java.lang.String sessionId) Reinstantiates a serialized session from the data passed in.
ClusterMessage	requestCompleted(java.lang.String sessionId) When the request has been completed, the replication valve will notify the manager, and the manager will decide whether any replication is needed or not.
void	sessionInvalidated(java.lang.String sessionId)
void	setCluster(CatalinaCluster cluster)
void	setDefaultMode(boolean defaultMode)
void	setDistributable(boolean dist) Set the distributable flag for the sessions supported by this Manager.
void	setExpireSessionsOnShutdown(boolean expireSessionsOnShutdown)
void	setName(java.lang.String name) Set the name of the manager, at host /context name and at engine hostname+/context
void	setNotifyListenersOnReplication(boolean notifyListenersOnReplication)
void	setPrintToScreen(boolean printtoscreen)
void	setSendClusterDomainOnly(boolean sendClusterDomainOnly)
void	setSynchronousReplication(boolean flag)
void	setUseDirtyFlag(boolean usedirtyflag)
void	start() Prepare for the beginning of active use of the public methods of this component.
void	stop() Gracefully terminate the active use of the public methods of this component.
void	unload() Override persistence since they don't go hand in hand with replication for now.
protected byte[]	writeSession(Session session) Serialize a session into a byte array This method simple calls the writeObjectData method on the session and returns the byte data from that call

Methods inherited from class org.apache.catalina.session.StandardManager

addLifecycleListener, doLoad, doUnload, file, findLifecycleListeners, getInfo, getMaxActiveSessions, getPathname, getRejectedSessions, load, propertyChange, removeLifecycleListener, setContainer, setMaxActiveSessions, setPathname, setRejectedSessions

Methods inherited from class org.apache.catalina.session.ManagerBase

add, addPropertyChangeListener, backgroundProcess, changeSessionId, createEmptySession, createSession, destroy, expireSession, findSession, findSessions, generateSessionId, getActiveSessions, getAlgorithm, getClassName, getContainer, getCreationTime, getDigest, getDomain, getDuplicates, getEngine, getEntropy, getExpiredSessions, getJvmRoute, getLastAccessedTime, getMaxActive, getMaxInactiveInterval, getNewSession, getObjectName, getProcessExpiresFrequency, getProcessingTime, getRandom, getRandomBytes, getRandomClass, getRandomFile, getSession, getSessionAttribute, getSessionAverageAliveTime, getSessionCounter, getSessionIdLength, getSessionMaxAliveTime, init, listSessionIds, postDeregister, postRegister, preDeregister, preRegister, processExpires, remove, removePropertyChangeListener, setAlgorithm, setDuplicates, setEntropy, setExpiredSessions, setMaxActive, setMaxInactiveInterval, setProcessExpiresFrequency, setProcessingTime, setRandomClass, setRandomFile, setSessionAverageAliveTime, setSessionCounter, setSessionIdLength, setSessionMaxAliveTime

Methods inherited from class java.lang.Object

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

Methods inherited from interface org.apache.catalina.Manager

add, addPropertyChangeListener, backgroundProcess, changeSessionId, createEmptySession, createSession, findSession, findSessions, getActiveSessions, getContainer, getExpiredSessions, getInfo, getMaxActive, getMaxInactiveInterval, getRejectedSessions, getSessionAverageAliveTime, getSessionCounter, getSessionIdLength, getSessionMaxAliveTime, load, remove, removePropertyChangeListener, setContainer, setExpiredSessions, setMaxActive, setMaxInactiveInterval, setRejectedSessions, setSessionAverageAliveTime, setSessionCounter, setSessionIdLength, setSessionMaxAliveTime

Field Detail

log

public static org.apache.commons.logging.Log log

mChannelConfig

protected java.lang.String mChannelConfig

mGroupName

protected java.lang.String mGroupName

mChannelStarted

protected boolean mChannelStarted

mPrintToScreen

protected boolean mPrintToScreen

defaultMode

protected boolean defaultMode

mManagerRunning

protected boolean mManagerRunning

synchronousReplication

protected boolean synchronousReplication

Use synchronous rather than asynchronous replication. Every session modification (creation, change, removal etc) will be sent to all members. The call will then wait for max milliseconds, or forever (if timeout is 0) for all responses.

mExpireSessionsOnShutdown

protected boolean mExpireSessionsOnShutdown

Set to true if we don't want the sessions to expire on shutdown

useDirtyFlag

protected boolean useDirtyFlag

name

protected java.lang.String name

distributable

protected boolean distributable

cluster

protected CatalinaCluster cluster

invalidatedSessions

protected java.util.HashMap invalidatedSessions

stateTransferred

protected boolean stateTransferred

Flag to keep track if the state has been transferred or not Assumes false.

Constructor Detail

SimpleTcpReplicationManager

public SimpleTcpReplicationManager()

Constructor, just calls super()

Method Detail

isSendClusterDomainOnly

public boolean isSendClusterDomainOnly()

Specified by:

isSendClusterDomainOnly in interface ClusterManager

Returns:

Manager send only to same cluster domain.

setSendClusterDomainOnly

public void setSendClusterDomainOnly(boolean sendClusterDomainOnly)

Specified by:

setSendClusterDomainOnly in interface ClusterManager

Parameters:

sendClusterDomainOnly - The sendClusterDomainOnly to set.

isDefaultMode

public boolean isDefaultMode()

Specified by:

isDefaultMode in interface ClusterManager

Returns:

Returns the defaultMode.

setDefaultMode

public void setDefaultMode(boolean defaultMode)

Specified by:

setDefaultMode in interface ClusterManager

Parameters:

defaultMode - The defaultMode to set.

isManagerRunning

public boolean isManagerRunning()

setUseDirtyFlag

public void setUseDirtyFlag(boolean usedirtyflag)

setExpireSessionsOnShutdown

public void setExpireSessionsOnShutdown(boolean expireSessionsOnShutdown)

setCluster

public void setCluster(CatalinaCluster cluster)

Specified by:

setCluster in interface ClusterManager

getExpireSessionsOnShutdown

public boolean getExpireSessionsOnShutdown()

setPrintToScreen

public void setPrintToScreen(boolean printtoscreen)

setSynchronousReplication

public void setSynchronousReplication(boolean flag)

unload

public void unload()
            throws java.io.IOException

Override persistence since they don't go hand in hand with replication for now.

Specified by:

unload in interface Manager

Overrides:

unload in class StandardManager

Throws:

java.io.IOException - if an input/output error occurs

createSession

protected Session createSession(java.lang.String sessionId,
                                boolean notify,
                                boolean setId)

Creates a HTTP session. Most of the code in here is copied from the StandardManager. This is not pretty, yeah I know, but it was necessary since the StandardManager had hard coded the session instantiation to the a StandardSession, when we actually want to instantiate a ReplicatedSession
If the call comes from the Tomcat servlet engine, a SessionMessage goes out to the other nodes in the cluster that this session has been created.

Parameters:

notify - - if set to true the other nodes in the cluster will be notified. This flag is needed so that we can create a session before we deserialize a replicated one

See Also:

ReplicatedSession

createSession

public Session createSession(java.lang.String sessionId)

Construct and return a new session object, based on the default settings specified by this Manager's properties. The session id will be assigned by this method, and available via the getId() method of the returned session. If a new session cannot be created for any reason, return null.

Specified by:

createSession in interface Manager

Overrides:

createSession in class StandardManager

Throws:

java.lang.IllegalStateException - if a new session cannot be instantiated for any reason

sessionInvalidated

public void sessionInvalidated(java.lang.String sessionId)

getInvalidatedSessions

public java.lang.String[] getInvalidatedSessions()

Description copied from interface: ClusterManager

When the manager expires session not tied to a request. The cluster will periodically ask for a list of sessions that should expire and that should be sent across the wire.

Specified by:

getInvalidatedSessions in interface ClusterManager

Returns:

String[] The invalidated sessions

requestCompleted

public ClusterMessage requestCompleted(java.lang.String sessionId)

Description copied from interface: ClusterManager

When the request has been completed, the replication valve will notify the manager, and the manager will decide whether any replication is needed or not. If there is a need for replication, the manager will create a session message and that will be replicated. The cluster determines where it gets sent.

Specified by:

requestCompleted in interface ClusterManager

Parameters:

sessionId - - the sessionId that just completed.

Returns:

a SessionMessage to be sent.

writeSession

protected byte[] writeSession(Session session)

Serialize a session into a byte array
This method simple calls the writeObjectData method on the session and returns the byte data from that call

Parameters:

session - - the session to be serialized

Returns:

a byte array containing the session data, null if the serialization failed

readSession

protected Session readSession(byte[] data,
                              java.lang.String sessionId)

Reinstantiates a serialized session from the data passed in. This will first call createSession() so that we get a fresh instance with all the managers set and all the transient fields validated. Then it calls Session.readObjectData(byte[]) to deserialize the object

Parameters:

data - - a byte array containing session data

Returns:

a valid Session object, null if an error occurs

getName

public java.lang.String getName()

Description copied from interface: ClusterManager

Return the name of the manager, at host /context name and at engine hostname+/context.

Specified by:

getName in interface ClusterManager

Overrides:

getName in class StandardManager

start

public void start()
           throws LifecycleException

Prepare for the beginning of active use of the public methods of this component. This method should be called after configure(), and before any of the public methods of the component are utilized.
Starts the cluster communication channel, this will connect with the other nodes in the cluster, and request the current session state to be transferred to this node.

Specified by:

start in interface Lifecycle

Overrides:

start in class StandardManager

Throws:

java.lang.IllegalStateException - if this component has already been started

LifecycleException - if this component detects a fatal error that prevents this component from being used

stop

public void stop()
          throws LifecycleException

Gracefully terminate the active use of the public methods of this component. This method should be the last one called on a given instance of this component.
This will disconnect the cluster communication channel and stop the listener thread.

Specified by:

stop in interface Lifecycle

Overrides:

stop in class StandardManager

Throws:

java.lang.IllegalStateException - if this component has not been started

LifecycleException - if this component detects a fatal error that needs to be reported

setDistributable

public void setDistributable(boolean dist)

Description copied from interface: Manager

Set the distributable flag for the sessions supported by this Manager. If this flag is set, all user data objects added to sessions associated with this manager must implement Serializable.

Specified by:

setDistributable in interface Manager

Overrides:

setDistributable in class ManagerBase

Parameters:

dist - The new distributable flag

getDistributable

public boolean getDistributable()

Description copied from interface: Manager

Return the distributable flag for the sessions supported by this Manager.

Specified by:

getDistributable in interface Manager

Overrides:

getDistributable in class ManagerBase

messageReceived

protected void messageReceived(SessionMessage msg,
                               Member sender)

This method is called by the received thread when a SessionMessage has been received from one of the other nodes in the cluster.

Parameters:

msg - - the message received

sender - - the sender of the message, this is used if we receive a EVT_GET_ALL_SESSION message, so that we only reply to the requesting node

messageDataReceived

public void messageDataReceived(ClusterMessage cmsg)

Description copied from interface: ClusterManager

A message was received from another node, this is the callback method to implement if you are interested in receiving replication messages.

Specified by:

messageDataReceived in interface ClusterManager

Parameters:

cmsg - - the message received.

isStateTransferred

public boolean isStateTransferred()

setName

public void setName(java.lang.String name)

Description copied from interface: ClusterManager

Set the name of the manager, at host /context name and at engine hostname+/context

Specified by:

setName in interface ClusterManager

Parameters:

name -

isNotifyListenersOnReplication

public boolean isNotifyListenersOnReplication()

setNotifyListenersOnReplication

public void setNotifyListenersOnReplication(boolean notifyListenersOnReplication)

getCluster

public CatalinaCluster getCluster()

Specified by:

getCluster in interface ClusterManager