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Class JavaGroups.JavaStack.MessageProtocol

java.lang.Object
   |
   +----JavaGroups.JavaStack.Protocol
           |
           +----JavaGroups.JavaStack.MessageProtocol

public abstract class MessageProtocol

extends Protocol

implements Transport, RequestHandler

A protocol based on this template can send messages to all members and receive all, a single, n, or none responses. Requests directed towards the protocol can be handled by overriding method Handle.

Requests and responses are in the form of Messages, which would typically need to contain information pertaining to the request/response, e.g. in the form of objects contained in the message. To use remote method calls, use RpcProtocol instead.

Typical use of of a MessageProtocol would be when a protocol needs to interact with its peer protocols at each of the members' protocol stacks. A simple protocol like fragmentation, which does not need to interact with other instances of fragmentation, may simply subclass Protocol instead.

ALL

FIRST

MAJORITY

NONE

MessageProtocol()

CastMessage(Vector, Message, int, long)

Cast a message to all members, and wait for mode responses.

Down(Event)

An event is to be sent down the stack.

Handle(Message)

Processes a request destined for this layer.

Receive(long)

Send(Message)

Add header and pass down.

SendMessage(Message, int, long)

Sends a message to a single member (destination = msg.dest) and returns the response.

Up(Event)

An event was received from the layer below.

 public static final int FIRST

 public static final int ALL

 public static final int NONE

 public static final int MAJORITY

 public MessageProtocol()

 public RspList CastMessage(Vector dests,
                            Message msg,
                            int mode,
                            long timeout)

Cast a message to all members, and wait for mode responses. The responses are returned in a response list, where each response is associated with its sender.

Uses GroupRequest.

Parameters:

dests - The members to which then message is to be sent

msg - The message to be sent to n members

mode - The number of responses to wait for:

1. FIRST: return when 1 response has been received
2. ALL: wait for all responses (minus responses from suspected members)
3. NONE: don't wait for any responses (asynchronous, one-way message send)
4. MAJORITY: wait for a majority of the members to respond. If a members crashes during the wait, the majority is recomputed.

timeout - If 0: wait forever. Otherwise, wait for mode responses or timeout time.

Returns:

RspList A list of responses. Each response is an Object and associated to its sender.

 public Object SendMessage(Message msg,
                           int mode,
                           long timeout) throws Timeout, Suspected

Sends a message to a single member (destination = msg.dest) and returns the response. The message's destination must be non-zero !

 public Object Handle(Message req)

Processes a request destined for this layer. The return value is sent as response.

 public void Send(Message msg) throws Exception

Add header and pass down. Only used for sending responses (by RequestCorrelator).

 public Object Receive(long timeout) throws Exception

 public final void Up(Event evt)

An event was received from the layer below.

Overrides:

Up in class Protocol

 public final void Down(Event evt)

An event is to be sent down the stack.

Overrides:

Down in class Protocol

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