JSGI Specification, v0.2
JSGI middleware is typically a function that takes at least one other JSGI application and returns another function which is also a JSGI application.
REQUEST_METHOD: The HTTP request method, such as “GET” or “POST”. This cannot ever be an empty string, and so is always required.
SCRIPT_NAME: The initial portion of the request URL‘s “path” that corresponds to the application object, so that the application knows its virtual “location”. This may be an empty string, if the application corresponds to the “root” of the server.
PATH_INFO: The remainder of the request URL‘s “path”, designating the virtual “location” of the request‘s target within the application. This may be an empty string, if the request URL targets the application root and does not have a trailing slash. This value may be percent-encoded when I originating from a URL.
QUERY_STRING: The portion of the request URL that follows the ?, if any. May be empty, but is always required!
SERVER_PORT: When combined with
PATH_INFO, these variables can be used to complete the URL. Note, however, that
HTTP_HOST, if present, should be used in preference to
SERVER_NAMEfor reconstructing the request URL.
SERVER_PORTcan never be empty strings, and so are always required.
- HTTP_ Variables: Variables corresponding to the client-supplied HTTP request headers (i.e., variables whose names begin with HTTP_). The presence or absence of these variables should correspond with the presence or absence of the appropriate HTTP header in the request.
In addition to this, the JSGI environment must include these JSGI-specific variables:
jsgi.version: The Array [0,2], representing this version of JSGI.
jsgi.url_scheme: http or https, depending on the request URL.
jsgi.input: See below, the input stream.
jsgi.errors: See below, the error stream.
jsgi.multithread: true if the application object may be simultaneously invoked by another thread in the same process, false otherwise.
jsgi.multiprocess: true if an equivalent application object may be simultaneously invoked by another process, false otherwise.
jsgi.run_once: true if the server expects (but does not guarantee!) that the application will only be invoked this one time during the life of its containing process. Normally, this will only be true for a server based on CGI (or something similar).
The server or the application can store their own data in the environment, too. The keys must contain at least one dot, and should be prefixed uniquely. The prefix jsgi. is reserved for use with the JSGI core distribution and must not be used otherwise. The environment must not contain the keys
HTTP_CONTENT_LENGTH (use the versions without HTTP). The CGI keys (named without a period) must have String values. There are the following restrictions:
jsgi.versionmust be an array of Integers.
jsgi.url_schememust either be http or https.
- There must be a valid input stream in
- There must be a valid error stream in
REQUEST_METHODmust be a valid token.
SCRIPT_NAME, if non-empty, must start with /
PATH_INFO, if non-empty, must start with /
CONTENT_LENGTH, if given, must consist of digits only.
- One of
PATH_INFOmust be set.
PATH_INFOshould be / if
SCRIPT_NAMEnever should be /, but instead be empty.
The Input Stream
Must be an input stream.
The Error Stream
Must be an output stream.
The status, if parsed as integer, must be greater than or equal to 100.
There must be a
Content-Type, except when the Status is 1xx, 204 or 304, in which case there must be none given.
There must not be a Content-Length header when the Status is 1xx, 204 or 304.
The Body must respond to
forEach and must only yield objects which have a
toByteString method (including Strings and Binary objects). If the Body responds to
close, it will be called after iteration. The Body commonly is an array of Strings or ByteStrings.
This specification is adapted from the Rack specification (http://rack.rubyforge.org/doc/files/SPEC.html) written by Christian Neukirchen.
Some parts of this specification are adopted from PEP333: Python Web Server Gateway Interface v1.0 (www.python.org/dev/peps/pep-0333/).