Capstone: HTTP server

The spec

Expose the todo list over HTTP using OTP stdlib servers only. Three behaviors define the whole project.

• The server listens on port 4001 and answers on localhost.
• A GET route serves the todo list as a JSON string.
• Unknown paths answer with a not found status.

:inets httpd sketch

The sketch below starts a plain HTTP service on port 4001 with stdlib modules only. Read it as a shape, not a full production config: start the client library, then start the service with a small property list where the port stays clearly visible.

:inets.start() {:ok, _pid} = :httpd.start_service( port: 4001, server_name: ~c"todo", server_root: ~c"/tmp", document_root: ~c"/tmp", modules: [:mod_esi] )

Serve JSON routes

Each route is a function from request to response. The todos route returns a JSON string with a success status and a JSON content type set by the server module.

def list_json do "{\"todos\": []}" end

Build JSON by hand here to stay inside the standard library. A JSON package becomes worth adding only when hand-built strings start to sprawl.

Test with :httpc

Verify the route with the stdlib client. Start the server, request the todos path, and assert the success code plus the body shape.

{:ok, {{_, 200, _}, _, body}} = :httpc.request(:get, {~c"http://localhost:4001/todos", []}, [], []) assert to_string(body) == "{\"todos\": []}"

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Article author: Arthur Isaev