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doc/src/manual/cowboy_middleware.ezdoc

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+::: cowboy_middleware
+
+The `cowboy_middleware` behaviour defines the interface used
+by Cowboy middleware modules.
+
+Middlewares process the request sequentially in the order they
+are configured.
+
+:: Types
+
+: env() = [{atom(), any()}]
+
+The environment variable.
+
+One is created for every request. It is passed to each
+middleware module executed and subsequently returned,
+optionally with its contents modified.
+
+:: Callbacks
+
+: execute(Req, Env)
+	-> {ok, Req, Env}
+	| {suspend, Module, Function, Args}
+	| {halt, Req}
+	| {error, StatusCode, Req}
+
+Types:
+
+* Req = cowboy_req:req()
+* Env = env()
+* Module = module()
+* Function = atom()
+* Args = [any()]
+* StatusCode = cowboy:http_status()
+
+Execute the middleware.
+
+The `ok` return value indicates that everything went well
+and that Cowboy should continue processing the request. A
+response may or may not have been sent.
+
+The `suspend` return value will hibernate the process until
+an Erlang message is received. Note that when resuming, any
+previous stacktrace information will be gone.
+
+The `halt` return value stops Cowboy from doing any further
+processing of the request, even if there are middlewares
+that haven't been executed yet. The connection may be left
+open to receive more requests from the client.
+
+The `error` return value sends an error response identified
+by the `StatusCode` and then proceeds to terminate the
+connection. Middlewares that haven't been executed yet
+will not be called.