rice.scribe
Class Topic

java.lang.Object
  rice.scribe.Topic

public class Topic

extends java.lang.Object

Field Summary

static int	CREATED The two states in which Topic can be.
static int	JOINING
protected java.util.Set	m_apps Set of IScribeApps that have subscribed to this Topic.
protected java.util.Set	m_children Set of NodeHandle objects for the local node's children in this topic's multicast subtree rooted at the local node.
int	m_heartBeatsMissed This keeps track of the number of heartbeat messages missed corresponding to this topic.
protected NodeHandle	m_parent Local node's parent in this topic's multicast tree
Scribe	m_scribe The scribe object on which this topic resides.
int	m_state Current state of Topic.
protected NodeId	m_topicId This topic's identifier
protected boolean	m_topicManager Indicates whether this node is manager of this topic.
protected boolean	m_wantUnsubscribe Flag indicating if the local node is waiting to be unsubscribed (because it still does not know parent)

Constructor Summary

Topic(NodeId topicId, Scribe scribe)
Constructs an empty Topic

Method Summary

boolean	addChild(NodeHandle child, ScribeMessage msg) Adds a node to the Set of children in this topic's multicast subtree rooted at this node
boolean	addChild(NodeHandle child, ScribeMessage msg, java.io.Serializable data) Adds a node to the Set of children in this topic's multicast subtree rooted at this node.
void	addToScribe() Creates a topic reference on the current Scribe node.
IScribeApp[]	getApps() Gets all the applications that wish to receive events regarding this Topic.
java.util.Vector	getChildren() This returns the most current view of the children in this topic's multicast subtree rooted at the local node.
NodeHandle	getParent() Returns the local node's parent in this topic's multicast tree.
int	getState() Gets the current state of topic.
NodeId	getTopicId() Returns the topic's id
boolean	hasChildren() Indicates if the local node has children associated with this topic.
boolean	hasSubscribers() If this topic has any applications registered as subscribers.
boolean	isTopicManager() Return boolean indicating if the node is topic manager for the current topic.
boolean	isWaitingUnsubscribe() Returns true if the local node is waiting to be unsubscribed from this topic.
void	postponeParentHandler() Resets the number of heartbeat messages corresponding to this topic to zero.
boolean	removeChild(NodeHandle child, ScribeMessage msg) Removes a node from the Set of children in this topic's multicast subtree rooted at this node
void	removeFromScribe() Removes this topic reference on the current Scribe node.
void	setParent(NodeHandle parent) Sets the local node's parent in this topic's multicast tree.
void	setState(int state) Set the state of topic to state
void	subscribe(IScribeApp app) Register an application as a subscriber to this Topic, so that the application receives events related to the Topic.
void	topicManager(boolean topicMgr) Sets the flag indicating whether the current node is topic manager for this topic
void	unsubscribe(IScribeApp app) Unregister an application as a Subscriber to this Topic, so that the application no longer receives events regarding this Topic.
void	waitUnsubscribe(boolean wait) Sets flag indicating if the local node is waiting to be unsubscribed from this topic (because it does not yet know its parent)

Methods inherited from class java.lang.Object

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

Field Detail

m_topicId

protected NodeId m_topicId

This topic's identifier

m_children

protected java.util.Set m_children

Set of NodeHandle objects for the local node's children in this topic's multicast subtree rooted at the local node.

m_parent

protected NodeHandle m_parent

Local node's parent in this topic's multicast tree

m_wantUnsubscribe

protected boolean m_wantUnsubscribe

Flag indicating if the local node is waiting to be unsubscribed (because it still does not know parent)

m_topicManager

protected boolean m_topicManager

Indicates whether this node is manager of this topic.

m_apps

protected java.util.Set m_apps

Set of IScribeApps that have subscribed to this Topic.

m_heartBeatsMissed

public int m_heartBeatsMissed

This keeps track of the number of heartbeat messages missed corresponding to this topic. This value is INCREMENTED whenever a scheduleHB() method is invoked on the scribe object. The assumption is that simultaneously the scheduleHB() method is also being invoked on the other nodes including the parent for this topic. This value is RESET whenever the local node receives a heartbeat message, publish message or MessageAckOnSubscribe from the parent for the topic.

m_scribe

public Scribe m_scribe

The scribe object on which this topic resides.

CREATED

public static final int CREATED

The two states in which Topic can be. CREATED means that topic object is just created, and a subscription message was not sent to subscribe to the topicId. JOINING means topic object is created and also a subscribe message was also sent to subscribe to the topicId.

See Also:

Constant Field Values

JOINING

public static final int JOINING

See Also:

Constant Field Values

m_state

public int m_state

Current state of Topic. Can be either of these: 1) Created 2) Joining

Constructor Detail

Topic

public Topic(NodeId topicId,
             Scribe scribe)

Constructs an empty Topic

Parameters:

topicId - unique id for this topic.

scribe - the scribe system in which the topic resides.

Method Detail

getTopicId

public NodeId getTopicId()

Returns the topic's id

Returns:

topic's unique identifier

setState

public void setState(int state)

Set the state of topic to state

Parameters:

state - The state to which current topic should be set to.

getState

public int getState()

Gets the current state of topic.

addChild

public boolean addChild(NodeHandle child,
                        ScribeMessage msg)

Adds a node to the Set of children in this topic's multicast subtree rooted at this node

Parameters:

child - the node to be added as a child.

msg - the ScribeMessage which triggered this action, it can be SUBSCRIBE msg, or null if application on top of Scribe called addChild()

Returns:

true if the child was NOT already in the Set of children.

addChild

public boolean addChild(NodeHandle child,
                        ScribeMessage msg,
                        java.io.Serializable data)

Adds a node to the Set of children in this topic's multicast subtree rooted at this node. Also takes in a serializable data which will be sent along with the ACK to the child.

Parameters:

child - the node to be added as a child.

msg - the ScribeMessage which triggered this action, it can be SUBSCRIBE msg, or null if application on top of Scribe called addChild()

data - The serializable data.

Returns:

true if the child was NOT already in the Set of children.

removeChild

public boolean removeChild(NodeHandle child,
                           ScribeMessage msg)

Removes a node from the Set of children in this topic's multicast subtree rooted at this node

Parameters:

child - the child node to be removed from the multicast tree.

msg - the ScribeMessage which triggered this action, it can be UNSUBSCRIBE msg, or null if application on top of Scribe called removeChild() or this child became dead

Returns:

true if the child node was in the Set of children.

hasChildren

public boolean hasChildren()

Indicates if the local node has children associated with this topic.

Returns:

true if the local node has children associated with this topic.

getChildren

public java.util.Vector getChildren()

This returns the most current view of the children in this topic's multicast subtree rooted at the local node. Note that additions and deletions to the returned vector do not affect the actual children set maintained by the node.

Returns:

vector of nodeHandle objects.

setParent

public void setParent(NodeHandle parent)

Sets the local node's parent in this topic's multicast tree.

Parameters:

parent - the node to be the parent.

getParent

public NodeHandle getParent()

Returns the local node's parent in this topic's multicast tree.

Returns:

the parent node.

subscribe

public void subscribe(IScribeApp app)

Register an application as a subscriber to this Topic, so that the application receives events related to the Topic.

Parameters:

app - The application to be registered.

unsubscribe

public void unsubscribe(IScribeApp app)

Unregister an application as a Subscriber to this Topic, so that the application no longer receives events regarding this Topic.

Parameters:

app - The application to be unregistered.

hasSubscribers

public boolean hasSubscribers()

If this topic has any applications registered as subscribers.

Returns:

true if there is at least one application subscribed to this topic.

waitUnsubscribe

public void waitUnsubscribe(boolean wait)

Sets flag indicating if the local node is waiting to be unsubscribed from this topic (because it does not yet know its parent)

Parameters:

wait - value to set flag

isWaitingUnsubscribe

public boolean isWaitingUnsubscribe()

Returns true if the local node is waiting to be unsubscribed from this topic.

Returns:

true if local node is waiting to be unsubscribed from this topic.

topicManager

public void topicManager(boolean topicMgr)

Sets the flag indicating whether the current node is topic manager for this topic

Parameters:

topicMgr - value of the flag

isTopicManager

public boolean isTopicManager()

Return boolean indicating if the node is topic manager for the current topic.

Returns:

true if topic manager, false otherwise

postponeParentHandler

public void postponeParentHandler()

Resets the number of heartbeat messages corresponding to this topic to zero. This method is called when you get a heartbeat message or a publish message or a MessageAckOnSubscribe.

addToScribe

public void addToScribe()

Creates a topic reference on the current Scribe node. This method is called by ScribeMessage objects.

removeFromScribe

public void removeFromScribe()

Removes this topic reference on the current Scribe node. This method is called by ScribeMessage objects.

getApps

public IScribeApp[] getApps()

Gets all the applications that wish to receive events regarding this Topic.

Returns:

The applications currently registered with this Topic