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diff --git a/doc/src/guide/getting_started.asciidoc b/doc/src/guide/getting_started.asciidoc new file mode 100644 index 0000000..5d72f0a --- /dev/null +++ b/doc/src/guide/getting_started.asciidoc @@ -0,0 +1,136 @@ +[[getting_started]] +== Getting started + +Erlang is more than a language, it is also an operating system +for your applications. Erlang developers rarely write standalone +modules, they write libraries or applications, and then bundle +those into what is called a release. A release contains the +Erlang VM plus all applications required to run the node, so +it can be pushed to production directly. + +This chapter walks you through all the steps of setting up +Cowboy, writing your first application and generating your first +release. At the end of this chapter you should know everything +you need to push your first Cowboy application to production. + +=== Bootstrap + +We are going to use the https://github.com/ninenines/erlang.mk[Erlang.mk] +build system. It also offers bootstrap features allowing us to +quickly get started without having to deal with minute details. + +First, let's create the directory for our application. + +[source,bash] +$ mkdir hello_erlang +$ cd hello_erlang + +Then we need to download Erlang.mk. Either use the following +command or download it manually. + +[source,bash] +$ wget https://raw.githubusercontent.com/ninenines/erlang.mk/master/erlang.mk + +We can now bootstrap our application. Since we are going to generate +a release, we will also bootstrap it at the same time. + +[source,bash] +$ make -f erlang.mk bootstrap bootstrap-rel + +This creates a Makefile, a base application, and the release files +necessary for creating the release. We can already build and start +this release. + +[source,bash] +---- +$ make run +... +([email protected])1> +---- + +Entering the command `i().` will show the running processes, including +one called `hello_erlang_sup`. This is the supervisor for our +application. + +The release currently does nothing. In the rest of this chapter we +will add Cowboy as a dependency and write a simple "Hello world!" +handler. + +=== Cowboy setup + +Modifying the 'Makefile' allows the build system to know it needs to +fetch and compile Cowboy. To do that we simply need to add one line +to our Makefile to make it look like this: + +[source,make] +PROJECT = hello_erlang +DEPS = cowboy +include erlang.mk + +If you run `make run` now, Cowboy will be included in the release +and started automatically. This is not enough however, as Cowboy +doesn't do anything by default. We still need to tell Cowboy to +listen for connections. + +=== Listening for connections + +We will do this when our application starts. It's a two step process. +First we need to define and compile the dispatch list, a list of +routes that Cowboy will use to map requests to handler modules. +Then we tell Cowboy to listen for connections. + +Open the 'src/hello_erlang_app.erl' file and add the necessary +code to the `start/2` function to make it look like this: + +[source,erlang] +---- +start(_Type, _Args) -> + Dispatch = cowboy_router:compile([ + {'_', [{"/", hello_handler, []}]} + ]), + {ok, _} = cowboy:start_http(my_http_listener, 100, [{port, 8080}], + [{env, [{dispatch, Dispatch}]}] + ), + hello_erlang_sup:start_link(). +---- + +The dispatch list is explained in great details in the +xref:routing[Routing] chapter. For this tutorial we map the +path `/` to the handler module `hello_handler`. This module +doesn't exist yet, we still have to write it. + +If you build and start the release, then open http://localhost:8080 +in your browser, you will get an error because the module is missing. +Any other URL, like http://localhost:8080/test, will result in a +404 error. + +=== Handling requests + +Cowboy features different kinds of handlers, including REST +and Websocket handlers. For this tutorial we will use a plain +HTTP handler. + +First, let's generate a handler from a template. + +[source,bash] +$ make new t=cowboy_http n=hello_handler + +You can then open the 'src/hello_handler.erl' file and modify +the `init/2` function like this to send a reply. + +[source,erlang] +---- +init(Req, Opts) -> + Req2 = cowboy_req:reply(200, + [{<<"content-type">>, <<"text/plain">>}], + <<"Hello Erlang!">>, + Req), + {ok, Req2, Opts}. +---- + +What the above code does is send a `200 OK` reply, with the +`content-type` header set to `text/plain` and the response +body set to `Hello Erlang!`. + +If you run the release and open http://localhost:8080 +in your browser, you should get a nice `Hello Erlang!` displayed! |