Processing data sent to a custom handler

POST Method

Preliminaries

This note provides supplementary information about the server's implementation of the standard HTTP POST method to process data sent to the server for special handling.

The POST method is the protocol used by HTML forms to accept data for processing. It is the only method other than GET that is directly supported via HTML.

POST is dissimilar from PUT and PATCH in that the request's :path pseudo-header identifies a module to be used as a data handler. By way of constrast, the other two method's :path pseudo-header identifies the resource that is the target of the update.

In many programming paradigms the :path is both the data handler and the target resource. This is often termed a post-back. The RWSERVE software does not restrict POST methods one way or the other, so using post-backs is allowed, but not required.

When used in either an AJAX call, or with an HTTP <form method='POST'>, a software developer must write a custom module that will carry out the request to process the data, and the webmaster must configure a dynamic route with *methods=POST which references that module.

Request/response handlers

The server's request/response cycle for POST requests is fulfilled using this sequence of handlers:

	Request Handler	Optional	Configurable
1	Server Name Indication	no	no
2	Hosts	no	yes
3	IP Access	yes	yes
4	Resource Masks	yes	yes
5	Raw Path	no	no
6	Cookies	no	no
7	Forbidden	yes	yes
8	Cross Origin	yes	yes
9	RBAC	yes	yes
10	Content Length	no	no
11	Content Decoding	no	no
12	WWW Form Data	no	no
13	Multipart Form Data	no	no
	Dynamic Handler	Optional	Configurable
14	Router	yes	yes
	Response Handler	Optional	Configurable
15	Content Length	no	no
16	Status Codes	no	yes

Status codes

Successful responses are finalized by the dynamic module with any of these status codes:

200 "OK" when the response contains a payload and these response headers: content-type, content-length and optionally content-encoding.
204 "No Content" when the response has no payload.
207 "Multi Status" with a payload that has individual status codes for each part of the multipart request.
303 "See Other" when the processing is successful and the browser should issue a follow-on GET request to the URI declared in the response's location header.
307 "Temporary Redirect" when the processing is successful and the browser should issue a follow-on POST request to the URI declared in the response's location header.

Content length

POST requests must contain a content-length header. If not present, the request will fail with a status code of 411 and an information header of rw-content-length-missing.

The maximum size of a file to be uploaded is limited by the server to the size configured in restrictions/content-length-limit. If the file is too large, the request will fail with a status code of 413 and an information header of rw-content-length-limit.

Content encoding

POST requests may be uploaded in compressed form if the request includes an acceptable content-encoding header with a value of 'br', 'gzip' or 'deflate'. The uploaded request body will be decompressed and made available to plugin work orders in uncompressed form.

The request will fail with status code 406 if the Content Encoding module is not enabled or if the encoding value is not acceptable. An rw-content-decoding information header is added to this type of unsuccessful response.

Reference

For reference purposes, refer to IETF RFC 7231 Hypertext Transfer Protocol (HTTP/1.1): Semantics and Content section 4.3.3 for the basic protocol expected of HTTP POST requests.