From 1b863c350ba1f9b8ad1cb458df514ab0fe6bb127 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lo=C3=AFc=20Hoguin?= Date: Mon, 11 Dec 2017 11:27:17 +0100 Subject: Add documentation for Cowboy 2.2 --- docs/en/cowboy/2.2/guide/middlewares/index.html | 251 ++++++++++++++++++++++++ 1 file changed, 251 insertions(+) create mode 100644 docs/en/cowboy/2.2/guide/middlewares/index.html (limited to 'docs/en/cowboy/2.2/guide/middlewares') diff --git a/docs/en/cowboy/2.2/guide/middlewares/index.html b/docs/en/cowboy/2.2/guide/middlewares/index.html new file mode 100644 index 00000000..f0c604e5 --- /dev/null +++ b/docs/en/cowboy/2.2/guide/middlewares/index.html @@ -0,0 +1,251 @@ + + + + + + + + + + + + Nine Nines: Middlewares + + + + + + + + + + + + + + +
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Middlewares

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Cowboy delegates the request processing to middleware components. +By default, two middlewares are defined, for the routing and handling +of the request, as is detailed in most of this guide.

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Middlewares give you complete control over how requests are to be +processed. You can add your own middlewares to the mix or completely +change the chain of middlewares as needed.

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Cowboy will execute all middlewares in the given order, unless one +of them decides to stop processing.

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Usage

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Middlewares only need to implement a single callback: execute/2. +It is defined in the cowboy_middleware behavior.

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This callback has two arguments. The first is the Req object. +The second is the environment.

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Middlewares can return one of three different values:

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Of note is that when hibernating, processing will resume on the given +MFA, discarding all previous stacktrace. Make sure you keep the Req +and Env in the arguments of this MFA for later use.

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If an error happens during middleware processing, Cowboy will not try +to send an error back to the socket, the process will just crash. It +is up to the middleware to make sure that a reply is sent if something +goes wrong.

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Configuration

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The middleware environment is defined as the env protocol option. +In the previous chapters we saw it briefly when we needed to pass +the routing information. It is a list of tuples with the first +element being an atom and the second any Erlang term.

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Two values in the environment are reserved:

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    +listener contains the name of the listener +

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    +result contains the result of the processing +

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The listener value is always defined. The result value can be +set by any middleware. If set to anything other than ok, Cowboy +will not process any subsequent requests on this connection.

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The middlewares that come with Cowboy may define or require other +environment values to perform.

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You can update the environment by calling the cowboy:set_env/3 +convenience function, adding or replacing a value in the environment.

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Routing middleware

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The routing middleware requires the dispatch value. If routing +succeeds, it will put the handler name and options in the handler +and handler_opts values of the environment, respectively.

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Handler middleware

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The handler middleware requires the handler and handler_opts +values. It puts the result of the request handling into result.

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+ Cowboy + 2.2 + + User Guide +

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Navigation

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