Getting Started

This guide explains how to get started with Async::HTTP.

Installation

Add the gem to your project:

$ bundle add async-http

Core Concepts

• {ruby Async::HTTP::Client} is the main class for making HTTP requests.
• {ruby Async::HTTP::Internet} provides a simple interface for making requests to any server "on the internet".
• {ruby Async::HTTP::Server} is the main class for handling HTTP requests.
• {ruby Async::HTTP::Endpoint} can parse HTTP URLs in order to create a client or server.
• protocol-http provides the abstract HTTP protocol interfaces.

Usage

Making a Request

To make a request, use {ruby Async::HTTP::Internet} and call the appropriate method:

require 'async/http/internet/instance'

Sync do
	Async::HTTP::Internet.get("https://httpbin.org/get") do |response|
		puts response.read
	end
end

The following methods are supported:

Async::HTTP::Internet.methods(false)
# => [:patch, :options, :connect, :post, :get, :delete, :head, :trace, :put]

Using a block will automatically close the response when the block completes. If you want to keep the response open, you can manage it manually:

require 'async/http/internet/instance'

Sync do
	response = Async::HTTP::Internet.get("https://httpbin.org/get")
	puts response.read
ensure
	response&.close
end

As responses are streamed, you must ensure it is closed when you are finished with it.

Persistence

By default, {ruby Async::HTTP::Internet} will create a {ruby Async::HTTP::Client} for each remote host you communicate with, and will keep those connections open for as long as possible. This is useful for reducing the latency of subsequent requests to the same host. When you exit the event loop, the connections will be closed automatically.

Downloading a File

require 'async/http/internet/instance'

Sync do
	# Issue a GET request to Google:
	response = Async::HTTP::Internet.get("https://www.google.com/search?q=kittens")
	
	# Save the response body to a local file:
	response.save("/tmp/search.html")
ensure
	response&.close
end

Posting Data

To post data, use the post method:

require 'async/http/internet/instance'

data = {'life' => 42}

Sync do
	# Prepare the request:
	headers = [['accept', 'application/json']]
	body = JSON.dump(data)
	
	# Issues a POST request:
	response = Async::HTTP::Internet.post("https://httpbin.org/anything", headers, body)
	
	# Save the response body to a local file:
	pp JSON.parse(response.read)
ensure
	response&.close
end

For more complex scenarios, including HTTP APIs, consider using async-rest instead.

Timeouts

To set a timeout for a request, use the Task#with_timeout method:

require 'async/http/internet/instance'

Sync do |task|
	# Request will timeout after 2 seconds
	task.with_timeout(2) do
		response = Async::HTTP::Internet.get "https://httpbin.org/delay/10"
	ensure
		response&.close
	end
rescue Async::TimeoutError
	puts "The request timed out"
end

Making a Server

To create a server, use an instance of {ruby Async::HTTP::Server}:

require 'async/http'

endpoint = Async::HTTP::Endpoint.parse('http://localhost:9292')

Sync do |task|
	Async(transient: true) do
		server = Async::HTTP::Server.for(endpoint) do |request|
			::Protocol::HTTP::Response[200, {}, ["Hello World"]]
		end
		
		server.run
	end
	
	client = Async::HTTP::Client.new(endpoint)
	response = client.get("/")
	puts response.read
ensure
	response&.close
end