src/router_core/DESIGN

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=================
General Structure
=================

                       +--------------------------------+
                       | Router Core Thread (CT)        |
                       |                           -----------
                       |                                 |||||    ---> General Events
                 action queue                      -----------
    Async        ------------                           |
    Action   --->     ||||||| ->                        |
    Functions    ------------                    -----------
                       |                               |||||--
                       |                         -----------||--  ---> Connection Events
                       |    Forwarding Tables      -----------||
                       |                             -----------
                       |                                |
                       +--------------------------------+

    The above APIs are declared in include/qpid/dispatch/router_core.h

    The asynchronous action functions place an action on the action queue.  The core
    thread processes the actions serially.

    General callbacks are invoked on one of the IO threads using a zero-duration
    timer.  General callbacks are not specific to a connection context.

    Connection callbacks are invoked on a thread that is exclusively dedicated to a
    connection.  The body of a connection callback may safely access any object or data
    structure that is associated with the connection, including Proton data.  Multiple
    connections may be processed concurrently on separate threads.


===================
Router Core Objects
===================

  qdr_core_t

    Core object containing one core thread and offering the core API.

  qdr_subscription_t

    Local subscription for receiving messages in-process.  This is used by the
    router-control module and the management agent.

  qdr_connection_t
  qdr_link_t
  qdr_delivery_t

    Tracking objects for connections, links, and deliveries.  These must be linked with
    their corresponding external object:

        qdr_connection_t  <--->  qd_connection_t
        qdr_link_t        <--->  qd_link_t
        qdr_delivery_t    <--->  pn_delivery_t

    Linkage is accomplished using the TYPE_set_context() methods.

  qdr_terminus_t
  qdr_error_t
  qd_delivery_state_t

    The these objects are used to hold a copy of the relevent content
    of Proton terminus, condition, disposition, and error state
    objects.  These are needed to ensure that references to these
    Proton state objects are not held within the core thread where
    thread safety with Proton may be a problem.


=========
Core APIs
=========

  Router Control

    Interface to the router-control module which tracks remote routers, neighbor
    routers, computes the best next-hops for each remote router, and maintains the
    mapping of mobile addresses to remote routers.

      Actions:
        Add/Delete Router
        Set/Remove Neighbor Link
        Set/Remove Next Hop
        Set Valid Origins
        Map/Unmap Destination

      General Events:
        Mobile Added/Removed
        Link Lost

  In-process Subscription and Send

    Used by in-process components that need to communicate using AMQP message
    transfers.  This API provides a best-effort messaging capability.  It does not
    provide acknowledgement, settlement, or flow control.

      Actions:
        Subscribe/Unsubscribe
        Send To

      General Events:
        Receive

  Connection Actions

    Tracks the lifecycle of a connection.

      Actions:
        Opened/Closed
        Process (writable)

      General Events:
        Activate

  Link Actions

    Tracks the lifecycle of a link.

      Actions:
        First Attach
        Second Attach
        Detach
        Deliver/Deliver_To

      Connection Events:
        First Attach
        Second Attach
        Detach

  Delivery Actions

    Tracks the lifecycle of a delivery.

      Actions:
        Update Disposition
        Flow

      Connection Events:
        Update Disposition
        Flow

  Management Actions

    Provides asynchronous access to manageable entities inside the core thread's data
    structures.

      Actions:
        Create
        Delete
        Read
        Update
        Query

      General Events:
        Response

    This management API is used to manage addresses, link-routes etc.
    destinations.


====================
Forwarding Treatment
====================

  Transition from fanout/bias to a one-dimensional list of treatment:

    MULTICAST_FLOOD (not available to users)

        Messages are delivered to all subscribers via all unique paths.  If there is
        redundancy in the router topology, multiple copies of each message will be
        delivered to some destinations.

        This semantic behavior should be avoided (not exposed?).  It is needed for a
        subset of the protocol messages used for router control.

    MULTICAST_ONCE

        Messages are delivered to all subscribers once.  This uses the valid-origins in
        concert with the ingress-router message annotation to prevent deliveries from
        being delivered multiply.

    ANYCAST_CLOSEST

        Messages are delivered to one subscriber.  The chosen subscriber is the one
        that has the lowest hop-cost from the producer.  If there are multiple
        consumers with the same lowest cost, deliveries are spread across all of those
        subscribers in a round-robin manner.

    ANYCAST_BALANCED

        Messages are delivered to one subscriber.  The chosen subscriber is the one
        with the lowest number of unsettled deliveries regardless of its location in
        the network topology.

    LINK_BALANCED

        For link-routes.


===============
Address Classes
===============

  L - Local
  T - Topological
  A - Area
  R - Router
  M - Mobile
  C - Link Inbound
  D - Link Outbound
  Z - Configuration


=================
Management Schema
=================

org
  apache
    qpid
      dispatch
        allocator
        connection
        connector
        console
        container
        dummy
        listener
        log
        router
          address
          link
          node
          route           (proposed)


============================
Route Control Data Structure
============================