RM SENDER AND RECEIVER LOCATION WITHIN JBOSSWS STACK

RM Sender and Receiver must operate on top of the transport layer
so they are able to create and close new transport connections.

RM Sender and Receiver are RM entities which goal is to ensure
message delivery and reliability according to the specified RM policy.

The expected model of RM sender/receiver is:
 * It will be a separate thread responsible for accepting/returning
   messages from/to JBossWS messaging layer
 * It will persist all messages going through it
 * It will query messages in the RM store against specific conditions
 * It will create RM tasks and put it to the RM task queue when re/send is necessary

Picture of the client side follows (RM RECEIVER is similar):

         +-----------------------------------------------------------------------------------+
         |                                    RM CHANNEL                                     |
+---+    |                                                                                   |
|   |    |               +-----------+                    +---------+                        |
| J | send(request)      |           |  put(RM request)   |         |                        |
| B |------------------->|           |------------------->|   RM    |                        |
| O |    |               | RM SENDER |                    |  TASKS  |                        |
| S | return response    |           | return RM response |  QUEUE  |                        | 
| S |<-------------------|           |<---------+         |         |                        |
| W |    |               +-----------+          |         +---------+                        |
| S |    |                 |       A            |                 |                          |
|   |    |                 |       |            +----------+      |                          |
| M |    |                 |       |                       |      |                          |
| E |    | write(request)  | query | read(request)         |      |                          |
| S |    | write(response) |       | read(resposne)        |      | take RM task             |
| S |    |                 |       |                       |      |                          |
| A |    |                 V       |                       |      |                          |
| G |    |               +-----------+                 +---|------|------------------------+ |
| I |    |               |           |                 |   |      | RM THREAD POOL         | |
| N |    |               |  RM STORE |                 |   |      V                        | |
| G |    |               |           |                 | +----------+         +----------+ | |
|   |    |               +-----------+                 | | Thread 1 |   ...   | Thread N | | |
| L |    |                                             | +----------+         +----------+ | |
| A |    |                                             |   A      |                        | |
| Y |    |                                             +---|------|------------------------+ |
| E |    |                                                 |      |                          |
| R |    |                                   read(response)|      | write(request)           | 
|   |    |                                                 |      |                          |
+---+    |                                            +----|------|------------------------+ |
         |                                            |    |      V                        | |    +---+
         |                                            |    |    +-----------------------+  | |    |   |
         |                                            |    |    |     Output Stream     |-------->| N |
         |                                            |    |    +-----------------------+  | |    | E |
         |                                            |    |                               | |    | T |
         |                                            |    |      REMOTING TRANSPORT       | |    | W |
         |                                            |    |                               | |    | O |
         |                                            |  +---------------------+           | |    | R |
         |                                            |  |     Input Stream    |<-----------------| K |
         |                                            |  +---------------------+           | |    |   |
         |                                            |                                    | |    +---+
         |                                            +------------------------------------+ |
         |                                                                                   |
         +-----------------------------------------------------------------------------------+

Definitions:

NETWORK                 - Intranet or Internet network

JBOSSWS MESSAGING LAYER - JBossWS messaging layer

RM CHANNEL              - is responsible for message acceptance from the JBOSSWS MESSAGING LAYER.
                          Since this time this channel is responsible for reliable message delivery
                          and will comunicate with JBOSSWS MESSAGING LAYER accordingly
                          (i.e. ensuring message in order delivery etc ...)

RM STORE                - is responsible for persistent operations. It must be able to:
                           * write message and its associated metadata,
                           * read the message and its associated metadata,
                           * query the messages in the store according to the specified criteria
                          NOTE 1: Messages and their metadata must be fully de/serializable without
                          dependency on the context class loader. That means all messages will be 
                          de/serialized before putting them to the RM STORE.
                          NOTE 2: Messages and their metadata will be de/serialized in the same
                          thread that initiated the invocation because of the heavy use 
                          of ThreadLocals in the JBossWS invocation framework. (However this
                          requirement could be fixed by removing the ThreadLocal dependency)

RM TASKS QUEUE          - holds RM tasks identified by the RM SENDER/RECEIVER that have to
                          be send to the transport layer

RM THREAD POOL          - holds RM threads that are responsible for doing the tasks stored
                          in the RM TASKS QUEUE and execute them against REMOTING TRANSPORT

NOTE:

All this is about messages acceptance from the JBossWS messaging layer and ensuring the reliable
delivery to the network and than back to the mesaging layer. It is not about the RM message
creation on the SOAP layer. SOAP headers related to the WS-RM specification will be handled
on higher level.

IMPLEMENTATION LOCATION:

I decided that the most suitable place to put RM CHANNEL to is the RemotingConnectionImpl class.