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3.2. Addressing

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3.4. Management Schema

3.3. AMQP Mapping

Dispatch Router is an AMQP router and as such, it provides extensions, code-points, and semantics for routing over AMQP. This page documents the details of Dispatch Router’s use of AMQP.

3.3.1. Message Annotations

The following Message Annotation fields are defined by Dispatch Router:

Field Type Description
x-opt-qd.ingress string The identity of the ingress router for a message-routed message. The ingress router is the first router encountered by a transiting message. The router will, if this field is present, leave it unaltered. If the field is not present, the router shall insert the field with its own identity.
x-opt-qd.trace list of string The list of routers through which this message-routed message has transited. If this field is not present, the router shall do nothing. If the field is present, the router shall append its own identity to the end of the list.
x-opt-qd.to string To-Override for message-routed messages. If this field is present, the address in this field shall be used for routing in lieu of the to field in the message properties. A router may append, remove, or modify this annotation field depending on the policy in place for routing the message.
x-opt-qd.phase integer The address-phase, if not zero, for messages flowing between routers.

3.3.2. Source/Target Capabilities

The following Capability values are used in Sources and Targets.

Capability Description
qd.router This capability is added to sources and targets that are used for inter-router message exchange. This capability denotes a link used for router-control messages flowing between routers.
qd.router-data This capability is added to sources and targets that are used for inter-router message exchange. This capability denotes a link used for user messages being message-routed across an inter-router connection.

3.3.3. Dynamic-Node-Properties

The following dynamic-node-properties are used by Dispatch in Sources.

Property Description
x-opt-qd.address The node address describing the destination desired for a dynamic source. If this is absent, the router will terminate any dynamic receivers. If this address is present, the router will use the address to route the dynamic link attach to the proper destination container.

3.3.4. Addresses and Address Formats

The following AMQP addresses and address patterns are used within Dispatch Router.

3.3.4.1. Address Patterns

Pattern Description
_local/<addr> An address that references a locally attached endpoint. Messages using this address pattern shall not be routed over more than one link.
_topo/0/<router>/<addr>

An address that references an endpoint attached to a specific router node in the network topology. Messages with addresses that follow this pattern shall be routed along the shortest path to the specified router. Note that addresses of this form are a-priori routable in that the address itself contains enough information to route the message to its destination.

The ‘0’ component immediately preceding the router-id is a placeholder for an _area_ which may be used in the future if area routing is implemented.

<addr> A mobile address. An address of this format represents an endpoint or a set of distinct endpoints that are attached to the network in arbitrary locations. It is the responsibility of the router network to determine which router nodes are valid destinations for mobile addresses.

3.3.4.2. Supported Addresses

Address Description
$management The management agent on the attached router/container. This address would be used by an endpoint that is a management client/console/tool wishing to access management data from the attached container.
_topo/0/Router.E/$management The management agent at Router.E in area 0. This address would be used by a management client wishing to access management data from a specific container that is reachable within the network.
_local/qdhello The router entity in each of the connected routers. This address is used to communicate with neighbor routers and is exclusively for the HELLO discovery protocol.
_local/qdrouter The router entity in each of the connected routers. This address is used by a router to communicate with other routers in the network.
_topo/0/Router.E/qdrouter The router entity at the specifically indicated router. This address form is used by a router to communicate with a specific router that may or may not be a neighbor.

3.3.5. Implementation of the AMQP Management Specification

Qpid Dispatch is manageable remotely via AMQP. It is compliant with the emerging AMQP Management specification (draft 9).

Differences from the specification:

  • The name attribute is not required when an entity is created. If not supplied it will be set to the same value as the system-generated “identity” attribute. Otherwise it is treated as per the standard.
  • The REGISTER and DEREGISTER operations are not implemented. The router automatically discovers peer routers via the router network and makes their management addresses available via the standard GET-MGMT-NODES operation.