Req

Req is a batteries-included HTTP client for Elixir.

With just a couple lines of code:

Mix.install([
  {:req, "~> 0.5.0"}
])

Req.get!("https://api.github.com/repos/wojtekmach/req").body["description"]
#=> "Req is a batteries-included HTTP client for Elixir."

we get automatic response body decoding, following redirects, retrying on errors, and much more. Virtually all of the features are broken down into individual functions called steps. You can easily re-use and re-arrange built-in steps (see Req.Steps module) and write new ones.

Features

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

• Extensibility via request, response, and error steps.

• Request body compression (via compress_body step)

• Opt-in response body decompression (via compressed and decompress_body steps). Supports gzip, brotli, and zstd.

• Request body encoding. Supports urlencoded and multipart forms, and JSON. See encode_body.

• Automatic response body decoding (via decode_body step.)

• Encode params as query string (via put_params step.)

• Setting base URL (via put_base_url step.

• Templated request paths (via put_path_params step.)

• Basic, Digest, Bearer, and .netrc-based authentication (via auth step.)

• Range requests (via put_range) step.)

• Use AWS V4 Signature (via put_aws_sigv4) step.)

• Request body streaming (by setting body: enumerable.)

• Response body streaming (by setting into: fun | collectable | :self.)

• Follows redirects (via redirect step.)

• Retries on errors (via retry step.)

• Raise on unexpected response status (via expect step.)

• Verify response body against a checksum (via checksum step.)

• Basic HTTP caching (via cache step.)

• Easily create test stubs (see Req.Test.)

• Running against a plug (via run_plug step.)

• Pluggable adapters. By default, Req uses Finch (via run_finch step.)

Usage

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

Mix.install([
  {:req, "~> 0.5.0"}
])

Req.get!("https://api.github.com/repos/wojtekmach/req").body["description"]
#=> "Req is a batteries-included HTTP client for Elixir."

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

Here's an example POST with JSON data:

iex> Req.post!("https://httpbin.org/post", json: %{x: 1, y: 2}).body["json"]
%{"x" => 1, "y" => 2}

You can stream request body:

iex> stream = Stream.duplicate("foo", 3)
iex> Req.post!("https://httpbin.org/post", body: stream).body["data"]
"foofoofoo"

and stream the response body:

iex> resp = Req.get!("http://httpbin.org/stream/2", into: IO.stream())
# output: {"url": "http://httpbin.org/stream/2", ...}
# output: {"url": "http://httpbin.org/stream/2", ...}
iex> resp.status
200
iex> resp.body
%IO.Stream{}

(See Req module documentation for more examples of response body streaming.)

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.new/1 for more information on available options.

Virtually all of Req's features are 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. Importantly, steps are just regular functions. Here is another example where we append a request step that inspects the URL just before requesting it:

req =
  Req.new(base_url: "https://api.github.com")
  |> Req.Request.append_request_steps(
    debug_url: fn request ->
      IO.inspect(URI.to_string(request.url))
      request
    end
  )

Req.get!(req, url: "/repos/wojtekmach/req").body["description"]
# output: "https://api.github.com/repos/wojtekmach/req"
#=> "Req is a batteries-included HTTP client for Elixir."

Custom steps can be packaged into plugins so that they are even easier to use by others. See Related Packages.

Here is how they can be used:

Mix.install([
  {:req, "~> 0.5.0"},
  {:req_easyhtml, "~> 0.2.0"},
  {:req_s3, "~> 0.2.3"},
  {:req_hex, "~> 0.2.0"},
  {:req_github_oauth, "~> 0.1.0"}
])

req =
  (Req.new(http_errors: :raise)
  |> ReqEasyHTML.attach()
  |> ReqS3.attach()
  |> ReqHex.attach()
  |> ReqGitHubOAuth.attach())

Req.get!(req, url: "https://elixir-lang.org").body[".entry-summary h5"]
#=>
# #EasyHTML[<h5>
#    Elixir is a dynamic, functional language for building scalable and maintainable applications.
#  </h5>]

Req.get!(req, url: "s3://ossci-datasets/mnist/t10k-images-idx3-ubyte.gz").body
#=> <<0, 0, 8, 3, ...>>

Req.get!(req, url: "https://repo.hex.pm/tarballs/req-0.1.0.tar").body["metadata.config"]["links"]
#=> %{"GitHub" => "https://github.com/wojtekmach/req"}

Req.get!(req, url: "https://api.github.com/user").body["login"]
# output:
# paste this user code:
#
#   6C44-30A8
#
# at:
#
#   https://github.com/login/device
#
# open browser window? [Yn]
# 15:22:28.350 [info] response: authorization_pending
# 15:22:33.519 [info] response: authorization_pending
# 15:22:38.678 [info] response: authorization_pending
#=> "wojtekmach"

Req.get!(req, url: "https://api.github.com/user").body["login"]
#=> "wojtekmach"

See Req.Request module documentation for more information on low-level API, request struct, and developing plugins.

Configuration

Req supports many configuration options, see Req.new/1 for a full list and see each step for more details. In particular, if you are looking for slightly lower level HTTP options such as timeouts, pool sizes, and certificates, see the run_finch documentation.

Related Packages

There are many packages that extend the Req library. To get yours listed here, send a PR.

• req_easyhtml
• req_s3
• req_hex
• req_github_oauth
• curl_req
• http_cookie
• req_embed
• req_proxy

Presentations

• Building API Clients with Req -- ElixirConf EU 2024
• Req: A batteries-included HTTP client for Elixir -- ElixirConf 2023

Development

When developing on macOS, you may need the following linker flags in order to successfully compile Brotli.

export LDFLAGS="-undefined dynamic_lookup -dynamiclib"

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.