Quick Start

Installation

Add this line to your application’s Gemfile:

ruby

gem 'faraday'

And then execute:

bash

$ bundle

Or install it yourself as:

bash

$ gem install faraday

Usage

Quick requests

Let's fetch the home page for the wonderful httpbingo.org service.

You can make a simple GET request using Faraday.get:

ruby

response = Faraday.get('http://httpbingo.org')

This returns a Faraday::Response object with the response status, headers, and body.

ruby

response.status
# => 200

response.headers
# => {"server"=>"Fly/c375678 (2021-04-23)", "content-type"=> ...

response.body
# => "<!DOCTYPE html><html> ...

Faraday Connection

The recommended way to use Faraday, especially when integrating to 3rd party services and APIs, is to create a Faraday::Connection. The connection initializer allows you to set:

default request headers & query parameters
network settings like proxy or timeout
common URL base path
Faraday adapter & middleware (see below)

Create a Faraday::Connection by calling Faraday.new. You can then call each HTTP verb (get, post, ...) on your Faraday::Connection to perform a request:

ruby

conn = Faraday.new(
  url: 'http://httpbingo.org',
  params: {param: '1'},
  headers: {'Content-Type' => 'application/json'}
)

response = conn.post('/post') do |req|
  req.params['limit'] = 100
  req.body = {query: 'chunky bacon'}.to_json
end
# => POST http://httpbingo.org/post?param=1&limit=100

GET, HEAD, DELETE, TRACE

Faraday supports the following HTTP verbs that typically don't include a request body:

get(url, params = nil, headers = nil)
head(url, params = nil, headers = nil)
delete(url, params = nil, headers = nil)
trace(url, params = nil, headers = nil)

You can specify URI query parameters and HTTP headers when making a request.

ruby

response = conn.get('get', { boom: 'zap' }, { 'User-Agent' => 'myapp' })
# => GET http://httpbingo.org/get?boom=zap

POST, PUT, PATCH

Faraday also supports HTTP verbs with bodies. Instead of query parameters, these accept a request body:

post(url, body = nil, headers = nil)
put(url, body = nil, headers = nil)
patch(url, body = nil, headers = nil)

ruby

# POST 'application/x-www-form-urlencoded' content
response = conn.post('post', 'boom=zap')

# POST JSON content
response = conn.post('post', '{"boom": "zap"}',
  "Content-Type" => "application/json")

Posting Forms

Faraday will automatically convert key/value hashes into proper form bodies thanks to the url_encoded middleware included in the default connection.

ruby

# POST 'application/x-www-form-urlencoded' content
response = conn.post('post', boom: 'zap')
# => POST 'boom=zap' to http://httpbingo.org/post

Detailed HTTP Requests

Faraday supports a longer style for making requests. This is handy if you need to change many of the defaults, or if the details of the HTTP request change according to method arguments. Each of the HTTP verb helpers can yield a Faraday::Request that can be modified before being sent.

This example shows a hypothetical search endpoint that accepts a JSON request body as the actual search query.

ruby

response = conn.post('post') do |req|
  req.params['limit'] = 100
  req.headers['Content-Type'] = 'application/json'
  req.body = {query: 'chunky bacon'}.to_json
end
# => POST http://httpbingo.org/post?limit=100

Using Middleware

Configuring your connection or request with predefined headers and parameters is a good start, but the real power of Faraday comes from its middleware stack. Middleware are classes that allow you to hook into the request/response cycle and modify the request. They can help you with things like:

adding authentication headers
parsing JSON responses
logging requests and responses
raise errors on 4xx and 5xx responses
and much more!

For example, let's say you want to call an API that:

requires an authentication token in the Authorization header
expects JSON request bodies
returns JSON responses

and on top of that, you want to automatically raise errors on 4xx and 5xx responses, as well as log all requests and responses.

You can easily achieve all of the above by adding the necessary middleware to your connection:

ruby

conn = Faraday.new(url: 'http://httpbingo.org') do |builder|
  # Calls MyAuthStorage.get_auth_token on each request to get the auth token
  # and sets it in the Authorization header with Bearer scheme.
  builder.request :authorization, 'Bearer', -> { MyAuthStorage.get_auth_token }

  # Sets the Content-Type header to application/json on each request.
  # Also, if the request body is a Hash, it will automatically be encoded as JSON.
  builder.request :json

  # Parses JSON response bodies.
  # If the response body is not valid JSON, it will raise a Faraday::ParsingError.
  builder.response :json

  # Raises an error on 4xx and 5xx responses.
  builder.response :raise_error

  # Logs requests and responses.
  # By default, it only logs the request method and URL, and the request/response headers.
  builder.response :logger
end

# A simple example implementation for MyAuthStorage
class MyAuthStorage
  def self.get_auth_token
    rand(36 ** 8).to_s(36)
  end
end

The connection can now be used to make requests.

ruby

begin
  response = conn.post('post', { payload: 'this ruby hash will become JSON' })
rescue Faraday::Error => e
  # You can handle errors here (4xx/5xx responses, timeouts, etc.)
  puts e.response[:status]
  puts e.response[:body]
end

# At this point, you can assume the request was successful
puts response.body

# I, [2023-06-30T14:27:11.776511 #35368]  INFO -- request: POST http://httpbingo.org/post
# I, [2023-06-30T14:27:11.776646 #35368]  INFO -- request: User-Agent: "Faraday v2.7.8"
# Authorization: "Bearer wibzjgyh"
# Content-Type: "application/json"
# I, [2023-06-30T14:27:12.063897 #35368]  INFO -- response: Status 200
# I, [2023-06-30T14:27:12.064260 #35368]  INFO -- response: access-control-allow-credentials: "true"
# access-control-allow-origin: "*"
# content-type: "application/json; encoding=utf-8"
# date: "Fri, 30 Jun 2023 13:27:12 GMT"
# content-encoding: "gzip"
# transfer-encoding: "chunked"
# server: "Fly/a0b91024 (2023-06-13)"
# via: "1.1 fly.io"
# fly-request-id: "01H467RYRHA0YK4TQSZ7HS8ZFT-lhr"
# cf-team: "19ae1592b8000003bbaedcf400000001"

Faraday ships with a number of useful middleware, and you can also write your own. To learn more about middleware, please check the Middleware section.

Swapping Adapters

Faraday does not make HTTP requests itself, but instead relies on a Faraday adapter to do so. By default, it will use the Net::HTTP adapter, which is part of the Ruby standard library. Although Net::HTTP is the only adapter that ships with Faraday, there are many other adapters available as separate gems.

Once you have installed an adapter, you can use it by passing the adapter option to Faraday.new:

ruby

conn = Faraday.new(url: 'http://httpbingo.org') do |builder|
  builder.adapter :async_http
end

To learn more about adapters, including how to write your own, please check the Adapters section.

Default Connection, Default Adapter

Remember how we said that Faraday will automatically encode key/value hash bodies into form bodies? Internally, the top level shortcut methods Faraday.get, post, etc. use a simple default Faraday::Connection. The only middleware used for the default connection is :url_encoded, which encodes those form hashes, and the default_adapter.

You can change the default adapter or connection. Be careful because they're set globally.

ruby

Faraday.default_adapter = :async_http # defaults to :net_http

# The default connection has only `:url_encoded` middleware.
# Note that if you create your own connection with middleware, it won't encode
# form bodies unless you too include the :url_encoded middleware!
Faraday.default_connection = Faraday.new do |conn|
  conn.request :url_encoded
  conn.response :logger
  conn.adapter Faraday.default_adapter
end