Mint 🌱

Functional, low-level HTTP client for Elixir with support for HTTP/1 and HTTP/2.

Installation

To install Mint, add it to your mix.exs file:

defp deps do
  [
    {:mint, "~> 1.0"}
  ]
end

Then, run:

mix deps.get

Usage

Mint is different from most Erlang and Elixir HTTP clients because it provides a process-less architecture. Instead, Mint is based on a functional and immutable data structure that represents an HTTP connection. This data structure wraps a TCP or SSL socket. This allows for more fine-tailored architectures where the developer is responsible for wrapping the connection struct, such as having one process handle multiple connections or having different kinds of processes handle connections. You can think of Mint as :gen_tcp and :ssl, but with an understanding of the HTTP/1.1 and HTTP/2 protocols.

Let's see an example of a basic interaction with Mint. First, we start a connection through Mint.HTTP.connect/3:

iex> {:ok, conn} = Mint.HTTP.connect(:http, "httpbin.org", 80)

This transparently chooses between HTTP/1 and HTTP/2. Then, we can send requests with:

iex> {:ok, conn, request_ref} = Mint.HTTP.request(conn, "GET", "/", [], "")

The connection socket runs in active mode (with active: :once), which means that the user of the library needs to handle TCP messages and SSL messages:

iex> flush()
{:tcp, #Port<0.8>,
 "HTTP/1.1 200 OK\r\n" <> _}

Users are not supposed to examine these messages. Instead, Mint provides a stream/2 function that turns messages into HTTP responses. Mint streams responses back to the user in parts through response parts such as :status, :headers, :data, and :done.

iex> {:ok, conn} = Mint.HTTP.connect(:https, "httpbin.org", 443)
iex> {:ok, conn, request_ref} = Mint.HTTP.request(conn, "GET", "/", [], "")
iex> receive do
...>   message ->
...>     {:ok, conn, responses} = Mint.HTTP.stream(conn, message)
...>     IO.inspect(responses)
...> end
[
  {:status, #Reference<...>, 200},
  {:headers, #Reference<...>, [{"connection", "keep-alive"}, ...},
  {:data, #Reference<...>, "<!DOCTYPE html>..."},
  {:done, #Reference<...>}
]

In the example above, we get all the responses as a single SSL message, but that might not always be the case. This means that Mint.HTTP.stream/2 might not always return responses.

The connection API is stateless, which means that you need to make sure to always save the connection that functions return:

# Wrong ❌
{:ok, _conn, ref} = Mint.HTTP.request(conn, "GET", "/foo", [], "")
{:ok, conn, ref} = Mint.HTTP.request(conn, "GET", "/bar", [], "")

# Correct ✅
{:ok, conn, ref} = Mint.HTTP.request(conn, "GET", "/foo", [], "")
{:ok, conn, ref} = Mint.HTTP.request(conn, "GET", "/bar", [], "")

For more information, see the documentation.

SSL certificates

When using SSL, you can pass in your own CA certificate store. If one is not provided, Mint will use the one in your system, as long as you are using Erlang/OTP 25+. If none of these conditions are true, just add :castore to your dependencies.

defp deps do
  [
    # ...,
    {:castore, "~> 1.0.0"},
    {:mint, "~> 0.4.0"}
  ]
end

WebSocket Support

Mint itself does not support the WebSocket protocol, but it can be used as the foundation to build a WebSocket client on top of. If you need WebSocket support, you can use mint_web_socket.

Connection Management and Pooling

Mint is a low-level client. If you need higher-level features such as connection management, pooling, metrics, and more, check out Finch, a project built on top of Mint that provides those things.

Contributing

If you wish to contribute, check out the issue list and let us know what you want to work on, so that we can discuss it and reduce duplicate work.

Tests are organized with tags. Integration tests that hit real websites over the internet are tagged with :requires_internet_connection. Proxy tests are tagged with :proxy (excluded by default) and require that you start local proxy instance through Docker Compose (or Podman Compose) from the Mint root directory in order to run.

If you encounter {:error, %Mint.TransportError{reason: :nxdomain}} error during the integration test, this suggests your DNS-based adblocker (self-hosted or VPN) might be blocking social media sites used in the integration test cases.

Here are a few examples of running tests:

Run all default tests which including :requires_internet_connection except :proxy:

mix test

Local tests, if you don't have an Internet connection available:

mix test --exclude requires_internet_connection

Run all tests:

DOCKER_USER="$UID:$GID" docker compose up --detach # or podman-compose up --detach
mix test --include proxy

License

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

  https://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.

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