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This specification aims to formalize the Strata protocol for building web
applications using the node.js JavaScript platform. You can (and should) use
the strata.lint middleware to enforce it. When you develop middleware, be sure
to add a strata.lint before and after to catch all mistakes.
# Applications
A Strata application is a function that takes exactly two arguments: the
*environment* and a *callback*.
## The Environment
The environment is an object that contains CGI-like properties. It must include
the following:
- protocol The protocol used in the request (i.e. "http:" or
"https:"). This variable may never be an empty string and
is always required.
- protocolVersion The version of the protocol used in the request. This
variable may never be an empty string and is always
required.
- requestMethod The request method (e.g. "GET" or "POST"). This cannot
ever be an empty string, and is always required.
- requestTime A Date that indicates the time the request was received.
- serverName, When combined with scriptName and pathInfo these
serverPort variables may be used to reconstruct the original
request URL. Note, however, that if httpHost is present,
it should be used in preference to serverName. These
variables can never be empty strings, and are always
required.
- scriptName The initial portion of the request URL's "path" that
corresponds to the application, so that it knows its
virtual "location". This may be an empty string, if the
application corresponds to the "root" of the server.
- pathInfo The remainder of the request URL's "path", designating
the virtual "location" of the target resource within the
application. This may be an empty string if the request
URL targets the root of the application and does not
have a trailing slash. This value may be percent-encoded
when originating from a URL.
- queryString The portion of the request URL that follows the "?", if
any. May be an empty string, but is always required.
- http* 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. The remainder of
the property name will be the camel-cased version of the
original header name (e.g. "httpAccept" and
"httpUserAgent").
The environment must not contain the properties httpContentType or
httpContentLength (use contentType and contentLength instead).
In addition to these, the environment may include the following Strata-specific
properties:
- input An EventEmitter of data contained in the request body
- error A writable Stream for error output
- session An object containing session data
- strataVersion The current version of Strata as [major, minor, patch]
There are the following restrictions:
- protocol must be either "http:" or "https:"
- requestMethod must be a valid HTTP verb as an uppercase String
- requestTime must be a Date
- scriptName and pathInfo, if not empty, should start with a "/"
- scriptName should never be "/" but instead be empty
- pathInfo should be "/" if scriptName is empty
- contentLength, if given, must consist of digits only
- input must be an EventEmitter
- error must be a writable Stream
- strataVersion must be an array of integers
The application is free to modify the environment. Property names must be
prefixed uniquely. The prefix "strata" is reserved for use within the Strata
core distribution and other accepted specifications and is not available for
use elsewhere.
## The Callback
The callback is used to issue a response to the client and must be called with
exactly three arguments: the response *status*, HTTP *headers*, and *body*.
### The Status
The status must be an HTTP status code as a Number.
### The Headers
The headers must be an object whose properties are the names of HTTP headers in
their canonical form (i.e. "Content-Type" instead of "content-type"). Header
names may contain only letters, digits, "-", and "_" and must start with a
letter and must not end with a "-" or "_". If more than one value for a header
is required, the value for that property must be an array.
There must be a Content-Type header, except for 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,
or it must be "0".
### The Body
The body must be either a string or a readable Stream. If it is a Stream, the
response will be pumped through to the client.
# Credits
Some parts of this specification are adopted from PEP333: Python Web Server
Gateway Interface v1.0 (http://www.python.org/dev/peps/pep-0333/) and the Rack
specification (http://rack.rubyforge.org/doc/files/SPEC.html).