# Request Blueprint ## Request format ### Basic requests A request blueprint is a document containing a list of HTTP requests that a client can send to a server. Once the server receives the request blueprint, it **MUST** process all the HTTP requests in the blueprint to produce a single response containing the information of the responses to the blueprint requests. The request that sends the request blueprint is referenced as the master request or the root request. An example of a blueprint could look like this: ```json [ { "requestId": "req-1", "uri": "/restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51?fields=title", "action": "view", "headers": { "Accept": "application/json" } }, { "requestId": "req-2", "uri": "/deals?page[limit]=5", "action": "view", "headers": { "Accept": "application/vnd.api+json" } }, { "requestId": "req-3", "uri": "/stats", "action": "create", "body": "{\"visitor\":\"anonymoys\"}", "headers": { "Accept": "application/json", "Content-Type": "application/json" } } ] ``` The blueprint above represents three different requests that may be run in parallel by the server. These requests could transform into the following parallel HTTP requests. ```http GET /restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51 HTTP/1.1 Host: example.org Accept: application/vnd.api+json ``` ```http GET /restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51 HTTP/1.1 Host: example.org Accept: application/vnd.api+json ``` ```http POST /stats HTTP/1.1 Host: example.org Accept: application/json Content-Type: application/json {"visitor":"anonymoys"} ``` ### Payload format You **MUST** provide a `Content-Type` header when sending a request to the front controller that processes the request blueprint. The content type header will determine what format is used in the blueprint. All the examples in this document assume `application/json` as the content type. You **MAY** send the blueprint document as the payload in a `POST` request. Alternatively, you **MAY** also send it in a `GET` request as a [percent encoded](https://tools.ietf.org/html/rfc3986#section-2.1) string in a query string parameter with the name of `query`. The blueprint document **MUST** be an array of subrequests. Each one of these subrequests **SHOULD** contain at least the following properties: * `action`: this indicates the type of action this subrequest will execute. Common values for this property are `view`, `create`, `update`, `replace`, `delete`, `exists` and `discover`. * `uri`: the URI for the subrequest. Additionally the payload for a subrequest **MAY** contain the following properties: * `requestId`: a unique identifier for the subrequest. This will be used to match the subrequest with one of the partial responses. * `body`: the serialized content of the body for the subrequest. * `headers`: an object of key value pairs. Each key **MUST** be interpreted as a header name for the subrequest, and the values as the header value. * `waitFor`: contains the request ID from another request. Indicates that the current subrequest depends on the other subrequest. When this property is present, the that particular subrequest cannot be processed until the referenced request has generated a response. ### Sequential requests Many times it is necessary to use the information of previous requests in order to build the correct request. That happens because a given request has a dependency some other requests to be resolved first. That use case is solved by request dependencies and by response pointers. #### Request dependency Any request can express a dependency on the response of a previous request. To do so such request **SHOULD** express the dependency in the `waitFor` key. The contents of this property **WILL** contain the request ID this request depends on. One subrequest **CAN** only indicate a dependency to one other subrequest. If a subrequest depends on a collection of subrequests at the same time, then the user **MAY** turn that collection into a request blueprint. That will to convert that collection into a single subrequest that can be waited for. #### Response embedding Some subrequests need information that is only made available when a previous subrequest has been processed and turned into a response. In that situation a subrequest **CAN** contain a replacement token that **MUST** be resolved from responses to previous subrequests in the same blueprint. The format of the replacement token is: ``` {{/@}} ``` The replacement data will be extracted from the response to the request indicated by the request ID in the replacement token. The specific data in that response to be embedded will be selected using a data pointer. A data pointer is a string that specifies what part of the referenced response should be embedded in place of the token. The embedded data **SHOULD** be serialized into a string according to the content type specified for the master request. When the content type of the master request is set to `application/json` then the data pointer **SHOULD** conform to the JSON pointer specification [RFC 6901](https://tools.ietf.org/html/rfc6901). If the content type is set to `application/xml` then the data pointer **SHOULD** be an XPath 2.0 compatible with the [W3C specification](https://www.w3.org/TR/xpath20). Replacement tokens **SHOULD NOT** be used in the `requestId` or `waitFor` properties. #### Example The following example shows how you can make use of the response embedding in the request blueprint to express dependencies. ```json [ { "requestId": "req-1", "uri": "/restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51&fields=menus", "action": "view", "headers": { "Accept": "application/json" } }, { "requestId": "req-2", "waitFor": "req-1", "uri": "/menus/{{/req-1@/rels/menu/id}}", "action": "view", "headers": { "Accept": "application/json" } }, { "requestId": "req-3", "waitFor": "req-2", "uri": "/menus/{{/req-1@/rels/menu/id}}/courses/{{/req-2@/mainCourse/id}}", "action": "view", "headers": { "Accept": "application/json" } } ] ``` This example shows how the request for the restaurant menu needs information from the request to the response to _req-1_. It also shows that _req-3_ depends on both _req-1_ and _req-2_ to compose the request. # Response format Once all the requests have been processed and the corresponding responses have been generated, the server **MUST** give a single response to the master request containing the responses to all subrequests. The response **MUST** use the 207 response code for multiple status, since each partial response will specify the status for their requests. In addition to that the response to the master request will use the `multipart/related` MIME type as specified in [RFC 2387](https://tools.ietf.org/html/rfc2387). The response contents to the blueprint above could look like: ```http --e43889 Cache-Control: no-cache Content-Id: Content-Type: application/json Status: 200 {"attrs": {"name": "Foo restaurant"}, "rels": {"menu": {"id": "1234"}}} --e43889 Cache-Control: no-cache Content-Id: Content-Type: application/json Status: 200 {"mainCourse": {"id": "meat-pie"}, "desert": {"id": "9876"}} --e43889 Cache-Control: no-cache Content-Id: Content-Type: application/vnd.api+json Status: 200 {"ingredients": ["meat", "crust"]} --e43889-- ``` Whereas the response HTTP header for the content type specifies the delimiter, among other information, as: ```http Conten-Type: multipart/related; boundary="e43889", type=application/json ```