Subrequests

Tell the system to execute several requests in a single bootstrap. Then return all the things.

NOTE: Version 2 has been released and will unleash much more power thanks to JSON Path replacements. I will allow replacements to generate multiple responses for a single request.

node.js: If you are looking for Subrequests without blocking I/O consider installing the node.js implementation instead.

See this article explaining why you need this module, and how to use it.

Read the article Installation Subrequests relies on external PHP libraries. To install the drupal module and all the dependencies:

composer require drupal/subrequests:^3.0 Usage example The following example will create a tag and an article using the JSON API module in a single request. (The request would be almost identical when using core's RESTful Web Services).

Issue a POST request against /subrequests with the following body:

[ { "requestId": "req-1", "uri": "/jsonapi/taxonomy_term/tags", "action": "create", "body": "{\"data\":{\"type\":\"taxonomy_term--tags\",\"attributes\":{\"name\":\"My custom tag!\",\"description\":{\"value\":\"description of my custom tag.\"},\"weight\":8}}}", "headers": { "Accept": "application/vnd.api+json", "Content-Type": "application/vnd.api+json", "Authorization": "Basic YWRtaW46YWRtaW4=" } }, { "requestId": "req-2", "waitFor": ["req-1"], "uri": "/jsonapi/node/article", "action": "create", "body": "{\"data\":{\"type\":\"node--article\",\"attributes\":{\"title\":\"My custom title\",\"status\":\"1\",\"promote\":\"1\",\"sticky\":\"0\",\"default_langcode\":\"1\",\"body\":{\"value\":\"Custom value\",\"format\":\"plain_text\",\"summary\":\"Custom summary\"}},\"relationships\":{\"field_tags\":{\"data\":[{\"type\":\"taxonomy_term--tags\",\"id\":\"{{req-1.body@$.data.id}}\"}]}}}}", "headers": { "Accept": "application/vnd.api+json", "Content-Type": "application/vnd.api+json", "Authorization": "Basic YWRtaW46YWRtaW4=" } } ] Note that you can generate the "body": "{\"data\":…\"id\":\"0a4526df-8241-40f9-ada0-3ac0593d6e11\"}}}}}" by doing:

$body = json_encode([ "data" => [ "id" => "0a4526df-8241-40f9-ada0-3ac0593d6e11", … ], ]); $blueprint = json_encode([ 'requestId' => 'req-1', 'uri': '/jsonapi/taxonomy_term/tags', 'body': $body, … ]); You can also do the same in JavaScript using JSON.stringify instead of PHP's json_encode

See SPECIFICATION.md for a more up to date version of the request blueprint request/response formats.

Request blueprint 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:

[ { "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.

GET /restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51 HTTP/1.1 Host: example.org Accept: application/vnd.api+json GET /restaurants/886e3b86-fa53-4bb3-b2c2-3ed544f1cd51 HTTP/1.1 Host: example.org Accept: application/vnd.api+json 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 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:

{{/<request-id>.body@<json-path>}} 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 JSONPath expression.

JSONPath expression 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 JSONPath specification.

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.

[ { "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.body@$.rels.menu.id}}", "action": "view", "headers": { "Accept": "application/json" } }, { "requestId": "req-3", "waitFor": ["req-2"], "uri": "/menus/{{req-1.body@$.rels.menu.id}}/courses/{{req-2.body@$.courses[*].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.

The response contents to the blueprint above could look like:

NOTE: If you want the response to be JSON instead append _format=json to the request URL.

--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 {"courses": [{"id": "meat-pie"}, {"id": "roasted-fish"}], "desert": {"id": "9876"}} --e43889 Cache-Control: no-cache Content-Id: <req-3#uri{0}> Content-Type: application/vnd.api+json Status: 200 {"ingredients": ["meat", "crust"]} --e43889--Cache-Control: no-cache Content-Id: <req-3#uri{1}> Content-Type: application/vnd.api+json Status: 200 {"ingredients": ["fish", "vegetables"]} --e43889--

Notice how {{req-2.body@$.courses[*].id}} returns two items meat-pie and roasted-fish. That will have the effect of creating two different responses one for each replacement. Those responses are <req-3#uri{0}> and <req-3#uri{1}>

Whereas the response HTTP header for the content type specifies the delimiter, among other information, as:

Conten-Type: multipart/related; boundary="e43889", type=application/json Contenta CMS
This module is part of the Contenta CMS decoupled distribution and integrates with Contenta JS. Learn more about these projects:

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