Download and use precompiled NIFs safely with checksums.

Rustler Precompiled is a tool for library maintainers that rely on Rustler. It helps by removing the need to have the Rust compiler installed in the user's machine.

Check the Precompilation Guide for details.

Example

defmodule MyApp.MyNative do
  use RustlerPrecompiled,
    otp_app: :my_app,
    crate: "my_app_nif",
    base_url: "https://github.com/me/my_project/releases/download/v0.1.0",
    version: "0.1.0"
end

Options

• :otp_app - The OTP app name that the dynamic library will be loaded from.

• :crate - The name of Rust crate if different from the :otp_app. This is optional.

• :base_url - Location where to find the NIFs from. This should be one of the following:

  • A URL to a directory containing the NIFs. The name of the NIF will be appended to it and a GET request will be made. Works well with public GitHub releases.

  • A tuple of {URL, headers}. The headers should be a list of key-value pairs. This is useful when the NIFs are hosted in a private server.

  • A tuple of {module, function} where the function is an atom representing the function name in that module. It's expected a function of arity 1, where the NIF file name is given, and it should return a URL or a tuple of {URL, headers}. This should be used for all cases not covered by the above. For example when multiple requests have to be made, like when using a private GitHub release through the GitHub API, or when the URLs don't resemble a simple directory.

• :version - The version of precompiled assets (it is part of the NIF filename).

• :force_build - Force the build with Rustler. This is false by default, but if your :version is a pre-release (like "2.1.0-dev"), this option will always be set true. You can also configure this option by setting an application env like this:

  config :rustler_precompiled, :force_build, your_otp_app: true

  It is important to add the ":rustler" package to your dependencies in order to force the build. To do that, just add it to your mix.exs file:

  {:rustler, ">= 0.0.0", optional: true}

  In case you want to force the build for all packages using RustlerPrecompiled, you can set the application config :force_build_all, or the env var RUSTLER_PRECOMPILED_FORCE_BUILD_ALL (see details below):

  config :rustler_precompiled, force_build_all: true

• :targets - A list of targets supported by Rust for which precompiled assets are available. By default the following targets are configured:

  • aarch64-apple-darwin
  • aarch64-unknown-linux-gnu
  • aarch64-unknown-linux-musl
  • arm-unknown-linux-gnueabihf
  • riscv64gc-unknown-linux-gnu
  • x86_64-apple-darwin
  • x86_64-pc-windows-gnu
  • x86_64-pc-windows-msvc
  • x86_64-unknown-linux-gnu
  • x86_64-unknown-linux-musl

• :nif_versions - A list of OTP NIF versions for which precompiled assets are available. A NIF version is usually compatible with two OTP minor versions, and an older NIF is usually compatible with newer OTPs. The available versions are the following:

  • 2.14 - for OTP 21 and above.
  • 2.15 - for OTP 22 and above.
  • 2.16 - for OTP 24 and above.
  • 2.17 - for OTP 26 and above.

  By default the following NIF versions are configured:

  • 2.15

  Check the compatibiliy table between Elixir and OTP in: https://hexdocs.pm/elixir/compatibility-and-deprecations.html#compatibility-between-elixir-and-erlang-otp

• :max_retries - The maximum of retries before giving up. Defaults to 3. Retries can be disabled with 0.

• :variants - A map with alternative versions of a given target. This is useful to support specific versions of dependencies, such as an old glibc version, or to support restrict CPU features, like AVX on x86_64.

  The order of variants matters, because the first one that returns true is going to be selected. Example:

  %{"x86_64-unknown-linux-gnu" => [old_glibc: fn _config -> has_old_glibc?() end]}

In case "force build" is used, all options except the ones use by RustlerPrecompiled are going to be passed down to Rustler. So if you need to configure the build, check the Rustler options.

Environment variables

This project reads some system environment variables. They are all optional, but they can change the behaviour of this library at compile time of your project.

They are:

• HTTP_PROXY or http_proxy - Sets the HTTP proxy configuration.

• HTTPS_PROXY or https_proxy - Sets the HTTPS proxy configuration.

• HEX_CACERTS_PATH - Sets the path for a custom CA certificates file. If unset, defaults to CAStore.file_path/0.

• MIX_XDG - If present, sets the OS as :linux for the :filename.basedir/3 when getting an user cache dir.

• TARGET_ARCH - The CPU target architecture. This is useful for when building your Nerves project, where your host CPU is different from your target CPU.

  Note that Nerves sets this value automatically when building your project.

  Examples: arm, aarch64, x86_64, riscv64.

• TARGET_ABI - The target ABI (e.g., gnueabihf, musl). This is set by Nerves as well.

• TARGET_VENDOR - The target vendor (e.g., unknown, apple, pc). This is not set by Nerves. If any of the TARGET_ env vars is set, but TARGET_VENDOR is empty, then we change the target vendor to unknown that is the default value for Linux systems.

• TARGET_OS - The target operational system. This is always linux for Nerves.

• RUSTLER_PRECOMPILED_GLOBAL_CACHE_PATH - The global cache path directory. If set, it will ignore the default cache path resolution, thus ignoring MIX_XDG, and will try to fetch the artifacts from that path. In case the desired artifact is not found, a download is going to start.

  This variable is important for systems that cannot perform a download at compile time, like inside NixOS. It will require people to previously download the artifacts to that path.

• RUSTLER_PRECOMPILED_FORCE_BUILD_ALL - If set to "1" or "true", it will override the :force_build configuration for all packages, and will force the build for them all. You can set the :force_build_all configuration to true to have the same effect.

Note that all packages using RustlerPrecompiled will be affected by these environment variables.

For more details about Nerves env vars, see https://hexdocs.pm/nerves/environment-variables.html