VMware Cloud Director uses the system AMQP service to communicate with extension services. Messages to and from an extension service are formatted as JSON objects.

When it receives an extension request, the VMware Cloud Director REST service creates a message and sends it to the system AMQP service, specifying the exchange and routing key registered by the extension service. The extension service retrieves the message from a queue bound to the exchange it registered, processes the request, and returns a response to the common reply exchange.

AMQP Message Headers

Each message from VMware Cloud Director to a service includes both standard and custom AMQP headers.

Table 1. Extension Service AMQP Message Headers
Header Value
correlationId A standard AMQP header that provides a unique identifier for the message. The extension must supply the same correlationId in the corresponding response.
reply-to A standard AMQP header specifying the value that the extension must use as the routingKey in the response.
messageType A custom AMQP header. One of:
ProcessHttpRequest
Indicates that this message is a forwarded request.
ProcessHttpResponse
Indicates that this message is a forwarded response.
replyToExchange A custom AMQP header. The name of the AMQP exchange to which the extension should publish its response.

Property Names and Values

A request message contains all of the following name=value pairs.

Table 2. Extension Service AMQP Request Message Property Names and Values
Name Value
method The HTTP method (GET, PUT, POST, DELETE) used to make the request
id The unique id of this message
scheme The scheme (HTTP or HTTPS) specified in the request URL
protocol The protocol used to make the request
headers The request headers represented as a map of name:value pairs encoded as a JSON object in the form: 
name:value,name:value,...
queryString The entire query string, or null if the request did not include a query string.
localPort The local port to which the request was sent
remoteAddr The IP address of the requesting machine
remotePort The remote port from which the request was sent
localAddr The IP address to which the request was sent
request Always true in request messages
requestURI The request URL, without any query string it might have included
parameters always null
user The id of the VMware Cloud Director user who made the request
org The id of the VMware Cloud Director organization to which the requesting user belongs
rights A comma-separated list of id values for the VMware Cloud Director rights assigned to the requesting user.

The parameters, user, org, and rights properties provide the security context for the request, and are formatted as a separate JSON object, as shown in AMQP Message Format

A response message contains all of the following name=value pairs.

Table 3. Extension Service AMQP Response Message Property Names and Values
Name Value
id The unique id of this message
headers A comma-separated list of request headers in the form: 
name:value,name:value,...
statusCode The HTTP status code to return to the requester
body A base64-encoded response body
request Always false in response messages

AMQP Message Format

Assume an extension service that includes an API filter of the following form: 
<vmext:ApiFilter>
   <vmext:UrlPattern>/api/org/.*</vmext:UrlPattern>
</vmext:ApiFilter>
When VMware Cloud Director receives a request like this one: 
GET https://10.23.6.168:8443/api/org/a93c9db9-7471-3192-8d09-a8f7eeda85f9
it creates the following message and places it on the service's exchange. 
[
  {
    "method":"GET",
    "id":"32d5b9ec-5eef-4aa3-9375-b054018b0e30",
    "scheme":"https",
    "protocol":"HTTP/1.1",
    "headers":{"Cookie":"...", "User-Agent":"...", ...},
    "queryString":null,
    "localPort":8443,
    "remoteAddr":"10.23.6.168",
    "remotePort":60576,
    "localAddr":"10.100.1.40",
    "request":true,
    "requestUri":"/api/org/a93c9db9-7471-3192-8d09-a8f7eeda85f9"
  },
  {
    "parameters":null,
    "user":"urn:vcloud:user:8cdd352f-f831-4712-a1a3-9e061687c5c6",
    "org":"urn:vcloud:org:a93c9db9-7471-3192-8d09-a8f7eeda85f9",
    "rights":["urn:vcloud:right:0b8c8cd2-5af9-32ad-a0bd-dc356503a552",...]
  },
  null
]
The service returns a response containing a base64-encoded body. 
[
  {
    "id":"32d5b9ec-5eef-4aa3-9375-b054018b0e30",
    "headers":{"Date":"...", "Content-Type":"application/vnd.vmware.vcloud.org+xml;version=2.0"},
    "statusCode":200,
    "body":"base64-encoded-body",
    "request":false,
  }
]