Req

Docs

Req is an HTTP client with a focus on ease of use and composability, built on top of Finch.

(Note: This is the README for the current main branch. See README for Req v0.2.2)

Features

• An easy to use high-level API: Req, Req.request/1, Req.get!/2, Req.post!/2, etc.

• Extensibility via request, response, and error steps.

• Automatic body decompression (via compressed and decompress step)

• Automatic body encoding and decoding (via encode_body and decode_body steps)

• Encode params as query string (via put_params step)

• Basic, bearer, and .netrc authentication (via auth step)

• Range requests (via put_range) step)

• Follows redirects (via follow_redirects step)

• Retries on errors (via retry step)

• Basic HTTP caching (via put_if_modified_since step)

• Setting base URL (via put_base_url step)

• Running against a plug (via put_plug step)

• Pluggable adapters (see "Adapter" section in Req.Request module documentation)

Usage

The easiest way to use Req is with Mix.install/2 (requires Elixir v1.12+):

Mix.install([
  {:req, "~> 0.3.0"}
])

Req.get!("https://api.github.com/repos/elixir-lang/elixir").body["description"]
#=> "Elixir is a dynamic, functional language designed for building scalable and maintainable applications"

If you want to use Req in a Mix project, you can add the above dependency to your mix.exs.

If you are planning to make several similar requests, you can build up a request struct with desired common options and re-use it:

req = Req.new(base_url: "https://api.github.com")

Req.get!(req, url: "/repos/sneako/finch").body["description"]
#=> "Elixir HTTP client, focused on performance"

Req.get!(req, url: "/repos/elixir-mint/mint").body["description"]
#=> "Functional HTTP client for Elixir with support for HTTP/1 and HTTP/2."

See Req.request/1 for more information on available options.

How Req Works

Virtually all of Req's functionality is broken down into individual pieces - steps. Req works by running the request struct through these steps. You can easily reuse or rearrange built-in steps or write new ones.

There are three types of steps: request, response, and error.

Request steps are used to refine the data that will be sent to the server.

After making the actual HTTP request, we'll either get a HTTP response or an error. The request, along with the response or error, will go through response or error steps, respectively.

Nothing is actually executed until we run the pipeline with Req.Request.run/1.

The high-level API shown before:

Req.get!("https://api.github.com/repos/elixir-lang/elixir")

is equivalent to this composition of lower-level API functions and steps:

%Req.Request{method: :get, url: "https://api.github.com/repos/elixir-lang/elixir"}
|> Req.Request.append_request_steps([
  &Req.Steps.put_default_user_agent/1,
  # ...
])
|> Req.Request.append_response_steps([
  &Req.Steps.retry/1,
  &Req.Steps.follow_redirects/1,
  # ...
|> Req.Request.append_error_steps([
  &Req.Steps.retry/1,
  # ...
])
|> Req.Request.run!()

We can also build more complex flows like returning a response from a request step or an error from a response step. See Req.Request documentation for more information.

Acknowledgments

Req is built on top of Finch and is inspired by cURL, Requests, Tesla, and many other HTTP clients - thank you!

License

Copyright (c) 2021 Wojtek Mach

Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with the License. You may obtain a copy of the License at http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.