Package org.apache.catalina.tribes

Interface ChannelInterceptor

All Superinterfaces:

Heartbeat, MembershipListener

All Known Implementing Classes:

ChannelCoordinator, ChannelInterceptorBase, DomainFilterInterceptor, EncryptInterceptor, FragmentationInterceptor, GroupChannel, GzipInterceptor, MessageDispatchInterceptor, NonBlockingCoordinator, OrderInterceptor, SimpleCoordinator, StaticMembershipInterceptor, TcpFailureDetector, TcpPingInterceptor, ThroughputInterceptor, TwoPhaseCommitInterceptor

public interface ChannelInterceptor
extends MembershipListener, Heartbeat

A ChannelInterceptor is an interceptor that intercepts messages and membership messages in the channel stack. This allows interceptors to modify the message or perform other actions when a message is sent or received.

Interceptors are tied together in a linked list.

See Also:

• ChannelInterceptorBase

Nested Class Summary

Nested Classes

Modifier and Type	Interface	Description
static interface	ChannelInterceptor.InterceptorEvent

Method Summary

Modifier and Type	Method	Description
void	fireInterceptorEvent(ChannelInterceptor.InterceptorEvent event)	Fire an event.
Channel	getChannel()	Return the channel that is related to this interceptor
Member	getLocalMember(boolean incAliveTime)	Intercepts the Channel.getLocalMember(boolean) method
Member	getMember(Member mbr)	Intercepts the Channel.getMember(Member) method
Member[]	getMembers()	Intercepts the Channel.getMembers() method
ChannelInterceptor	getNext()	Retrieve the next interceptor in the list
int	getOptionFlag()	An interceptor can react to a message based on a set bit on the message options.
ChannelInterceptor	getPrevious()	Retrieve the previous interceptor in the list
boolean	hasMembers()	Intercepts the Channel.hasMembers() method
void	heartbeat()	The heartbeat() method gets invoked periodically to allow interceptors to clean up resources, time out object and perform actions that are unrelated to sending/receiving data.
void	messageReceived(ChannelMessage data)	The messageReceived is invoked when a message is received.
void	sendMessage(Member[] destination, ChannelMessage msg, InterceptorPayload payload)	The sendMessage method is called when a message is being sent to one more destinations.
void	setChannel(Channel channel)	Set the channel that is related to this interceptor
void	setNext(ChannelInterceptor next)	Set the next interceptor in the list of interceptors
void	setOptionFlag(int flag)	Sets the option flag
void	setPrevious(ChannelInterceptor previous)	Set the previous interceptor in the list
void	start(int svc)	Starts up the channel.
void	stop(int svc)	Shuts down the channel.

Methods inherited from interface org.apache.catalina.tribes.MembershipListener

memberAdded, memberDisappeared

Method Details

getOptionFlag

int getOptionFlag()

An interceptor can react to a message based on a set bit on the message options. When a message is sent, the options can be retrieved from ChannelMessage.getOptions() and if the bit is set, this interceptor will react to it.

A simple evaluation if an interceptor should react to the message would be:
boolean react = (getOptionFlag() == (getOptionFlag() & ChannelMessage.getOptions()));
The default option is 0, meaning there is no way for the application to trigger the interceptor. The interceptor itself will decide.

Returns:

int

See Also:

• ChannelMessage.getOptions()

setOptionFlag

void setOptionFlag(int flag)

Sets the option flag

Parameters:

flag - int

See Also:

• getOptionFlag()

setNext

void setNext(ChannelInterceptor next)

Set the next interceptor in the list of interceptors

Parameters:

next - ChannelInterceptor

getNext

ChannelInterceptor getNext()

Retrieve the next interceptor in the list

Returns:

ChannelInterceptor - returns the next interceptor in the list or null if no more interceptors exist

setPrevious

void setPrevious(ChannelInterceptor previous)

Set the previous interceptor in the list

Parameters:

previous - ChannelInterceptor

getPrevious

ChannelInterceptor getPrevious()

Retrieve the previous interceptor in the list

Returns:

ChannelInterceptor - returns the previous interceptor in the list or null if no more interceptors exist

sendMessage

void sendMessage(Member[] destination,
 ChannelMessage msg,
 InterceptorPayload payload)
          throws ChannelException

The sendMessage method is called when a message is being sent to one more destinations. The interceptor can modify any of the parameters and then pass on the message down the stack by invoking getNext().sendMessage(destination,msg,payload).

Alternatively the interceptor can stop the message from being sent by not invoking getNext().sendMessage(destination,msg,payload).

If the message is to be sent asynchronous the application can be notified of completion and errors by passing in an error handler attached to a payload object.

The ChannelMessage.getAddress contains Channel.getLocalMember, and can be overwritten to simulate a message sent from another node.

Parameters:

destination - Member[] - the destination for this message

msg - ChannelMessage - the message to be sent

payload - InterceptorPayload - the payload, carrying an error handler and future useful data, can be null

Throws:

ChannelException - if a serialization error happens.

See Also:

• ErrorHandler
• InterceptorPayload

messageReceived

void messageReceived(ChannelMessage data)

The messageReceived is invoked when a message is received. ChannelMessage.getAddress() is the sender, or the reply-to address if it has been overwritten.

Parameters:

data - ChannelMessage

heartbeat

void heartbeat()

The heartbeat() method gets invoked periodically to allow interceptors to clean up resources, time out object and perform actions that are unrelated to sending/receiving data.

Specified by:

heartbeat in interface Heartbeat

hasMembers

boolean hasMembers()

Intercepts the Channel.hasMembers() method

Returns:

boolean - if the channel has members in its membership group

See Also:

• Channel.hasMembers()

getMembers

Member[] getMembers()

Intercepts the Channel.getMembers() method

Returns:

the members

See Also:

• Channel.getMembers()

getLocalMember

Member getLocalMember(boolean incAliveTime)

Intercepts the Channel.getLocalMember(boolean) method

Parameters:

incAliveTime - boolean

Returns:

the member that represents this node

See Also:

• Channel.getLocalMember(boolean)

getMember

Member getMember(Member mbr)

Intercepts the Channel.getMember(Member) method

Parameters:

mbr - Member

Returns:

Member - the actual member information, including stay alive

See Also:

• Channel.getMember(Member)

start

void start(int svc)
    throws ChannelException

Starts up the channel. This can be called multiple times for individual services to start The svc parameter can be the logical or value of any constants

Parameters:

svc - one of:

• Channel.DEFAULT - will start all services
• Channel.MBR_RX_SEQ - starts the membership receiver
• Channel.MBR_TX_SEQ - starts the membership broadcaster
• Channel.SND_TX_SEQ - starts the replication transmitter
• Channel.SND_RX_SEQ - starts the replication receiver

Throws:

ChannelException - if a startup error occurs or the service is already started.

See Also:

• Channel

stop

void stop(int svc)
   throws ChannelException

Shuts down the channel. This can be called multiple times for individual services to shutdown The svc parameter can be the logical or value of any constants

Parameters:

svc - one of:

• Channel.DEFAULT - will shutdown all services
• Channel.MBR_RX_SEQ - stops the membership receiver
• Channel.MBR_TX_SEQ - stops the membership broadcaster
• Channel.SND_TX_SEQ - stops the replication transmitter
• Channel.SND_RX_SEQ - stops the replication receiver

Throws:

ChannelException - if a startup error occurs or the service is already started.

See Also:

• Channel

fireInterceptorEvent

void fireInterceptorEvent(ChannelInterceptor.InterceptorEvent event)

Fire an event.

Parameters:

event - the event

getChannel

Channel getChannel()

Return the channel that is related to this interceptor

Returns:

Channel

setChannel

void setChannel(Channel channel)

Set the channel that is related to this interceptor

Parameters:

channel - The channel