Sagittarius module for NGINX

This repository provides Sagittarius module for NGINX. Using this, users can write web application in Scheme easily.

Requirements

This module requires Sagittarius 0.9.6. The later version may work as long as the undocumented C APIs aren't changed.

How to build

The module can only be built on POSIX environment (e.g. Linux, macOS).

It provides Makefile to detect and build automatically so simply run the following command:

$ make

The module will be built in the ./build/nginx-*$version*/objs/ directory with the name of ngx_http_sagittarius_module.so. The $version is currently 1.16.0.

If you want to run example application, then execute the run target. The run target also requires docker. If you don't have it, just modify it.

NGINX config

The module is built as a dynamic module, so add the following line:

load_module modules/ngx_http_sagittarius_module.so;

The module extends the location directive. The following example adds a simple web application:

location /echo {
  sagittarius run init clean {
    load_path /opt/share/;
	library "(echo)";
  }
}

The sagittarius directive specifies that the location is handled by the module. After the directive, it accepts 1 to 3 arguments; entry point, context initialisation, and clean up. The first one is mandatory and the rest are optional. All arguments must be exported procedures from the library specified library directive, if specified.

Directives

• sagittarius entry [init] [cleanup] - required

This directive must be inside of a location directive. It is illegal to put more than one sagittarius directive in one location directive.

The directive is a block directive, and it must have a library directive inside.

The specified location will be an entry point of the entry procedure which must be defined in the specified library. (The library name must be specified by the library directive.) The entry procedure is called with 2 arguments, NGINX request and NGINX response, and must return 2 values, status and content type.

If the optional init and cleanup are specified, then they will be called on the very first time of the HTTP request and when the worker process is terminating, respectively.

The init and cleanup procedures are called with one argument, NGINX context.

NOTE: The cleanup is only called if the init is called even if the worker process is terminating.

• library name - required

The library which provides entry described in the sagittarius directive.

• load_path path1 [paths ...] - optional

Specifiying load path. This directive can occure multiple times.

• parameter name value - optional

Adding a context parameter named name with value of value. This is useful if users want to share the same values per context.

Glossaries:

• context: An application context. A context contains the same information among the worker processes. This is equivalent with the location path.

Scheme APIs

The Scheme APIs provides accessor of the HTTP request, response and NGIN context.

HTTP request

All the HTTP request access procedures are prefixed with nginx-request-.

• (nginx-request? obj):

  Returns #t if the given *obj is a HTTP request otherwiese #f.

• (nginx-request-input-port request):

  Returns binary input port of transfered data. This procedure always returns an binary input port. If it's a GET request, reading a data always returns EOF.

• (nginx-request-context request):

  Returns NGINX context of this HTTP request.

• (nginx-request-method request):

  Retunrs HTTP method of this request as a string value.

• (nginx-request-uri request):

  Returns URI of this request.

• (nginx-request-headers request):

  Returns alist of HTTP header name and its value.

• (nginx-request-cookies request):

  Returns a list of HTTP cookies of (rfc cookies).

• (nginx-request-query-string request):

  Returns a query string of the HTTP request.

• (nginx-request-original-uri request):

  Returns the original URI of the HTTP request. The returning value may contain query string and fragment.

• (nginx-request-request-line request):

  Returns the first line of the HTTP reuqest.

The followings are the convenient procedures to access HTTP headers. The procedure name itself should be descriptive enough to see which HTTP headers are returned by the procedures.

• (nginx-request-host request):
• (nginx-request-connection request):
• (nginx-request-if-modified-since request):
• (nginx-request-if-unmodified-since request):
• (nginx-request-if-match request):
• (nginx-request-if-none-match request):
• (nginx-request-user-agent request):
• (nginx-request-referer request):
• (nginx-request-content-length request):
• (nginx-request-content-range request):
• (nginx-request-content-type request):
• (nginx-request-range request):
• (nginx-request-if-range request):
• (nginx-request-transfer-encoding request):
• (nginx-request-te request):
• (nginx-request-expect request):
• (nginx-request-upgrade request):
• (nginx-request-accept-encoding request):
• (nginx-request-via request):
• (nginx-request-authorization request):
• (nginx-request-keep-alive request):
• (nginx-request-accept request):
• (nginx-request-accept-language request):

HTTP response

• (nginx-response? obj):

  Returns #t if the given *obj is a HTTP response otherwiese #f.

• (nginx-response-output-port response):

  Returns binary output port of this HTTP response. This output port represents the response content. Thus, writing to this port means returning content to the client.

• (nginx-response-headers response):

  Reuturns alist of HTTP headers of the response. The result may or may not be freshly created.

• (nginx-response-header-add! response name value):

  Adding an HTTP header of name with value value.

  This procedure appends the header.

• (nginx-response-header-set! response name value):

  Setting an HTTP header of name with value value.

  This procedure replaces existing header(s).

• (nginx-response-header-remove! response name):

  Removes an HTTP header of name if exists.

NGINX context

• (nginx-context? context):

Returns #t if the given obj is a NGINX context otherwiese #f.

• (nginx-context-path context)

  Returns the application context path of the given context.

  The value shall be the same as the path specified in location directive.

• (nginx-context-parameter-ref context name)

  Returns the parameter value associated to name from the context. If the parameter doesn't exist, then returns #f.

  The parameter value is always a string.

• (nginx-context-parameters context):

  Returns an immutable hash table which contains all parameters of the context.