内容简介:The first step is to install Nix. If you are using a Linux machine, run this script:This will prompt you for more information as it goes on, so be sure to follow the instructions carefully. Once it is done, close and re-open your shell. After you have done
Nix is a tool that helps people create reproducible builds. This means that given the a known input, you can get the same output on other machines.Let’s build and deploy a small Rust service with Nix. This will not require the Rust compiler to be installed with rustup or similar.
- Setting up your environment
- A new project
- Setting up the Rust compiler
- Serving HTTP
- A simple package build
- Shipping it in a docker image
Setting up your environment
The first step is to install Nix. If you are using a Linux machine, run this script:
$ curl https://nixos.org/nix/install | sh
This will prompt you for more information as it goes on, so be sure to follow
the instructions carefully. Once it is done, close and re-open your shell. After
you have done this, nix-env
should exist in your shell. Try to run it:
$ nix-env error: no operation specified Try 'nix-env --help' for more information.
Let’s install a few other tools to help us with development. First, let’s install lorri to help us manage our development shell:
$ nix-env --install --file https://github.com/target/lorri/archive/master.tar.gz
This will automatically download and build lorri for your system based on the latest possible version. Once that is done, open another shell window (the lorri docs include ways to do this more persistently, but this will work for now) and run:
$ lorri daemon
Now go back to your main shell window and install direnv :
$ nix-env --install direnv
Next, follow the shell setup
needed for your shell. I personally
use fish
with oh my fish
, so I would run this:
$ omf install direnv
Finally, let’s install niv to help us handle dependencies for the project. This will allow us to make sure that our builds pin everything to a specific set of versions, including operating system packages.
$ nix-env --install niv
Now that we have all of the tools we will need installed, let’s create the project.
A new project
Go to your favorite place to put code and make a new folder. I personally prefer ~/code
, so I will be using that here:
$ cd ~/code $ mkdir helloworld $ cd helloworld
Let’s set up the basic skeleton of the project. First, initialize niv:
$ niv init
This will add the latest versions of niv
itself and the packages used for the
system to nix/sources.json
. This will allow us to pin exact versions so the
environment is as predictable as possible. Sometimes the versions of software in
the pinned nixpkgs are too old. If this happens, you can update to the
“unstable” branch of nixpkgs with this command:
$ niv update nixpkgs -b nixpkgs-unstable
Next, set up lorri using lorri init
:
$ lorri init
This will create shell.nix
and .envrc
. shell.nix
will be where we define
the development environment for this service. .envrc
is used to tell direnv
what it needs to do. Let’s try and activate the .envrc
:
$ cd . direnv: error /home/cadey/code/helloworld/.envrc is blocked. Run `direnv allow` to approve its content
Let’s review its content:
$ cat .envrc eval "$(lorri direnv)"
This seems reasonable, so approve it with direnv allow
like the error message
suggests:
$ direnv allow
Now let’s customize the shell.nix
file to use our pinned version of nixpkgs.
Currently, it looks something like this:
# shell.nix let pkgs = import <nixpkgs> {}; in pkgs.mkShell { buildInputs = [ pkgs.hello ]; }
This currently imports nixpkgs from the system-level version of it. This means
that different systems could have different versions of nixpkgs on it, and that
could make the shell.nix
file hard to reproduce between machines. Let’s import
the pinned version of nixpkgs that niv created:
# shell.nix let sources = import ./nix/sources.nix; pkgs = import sources.nixpkgs {}; in pkgs.mkShell { buildInputs = [ pkgs.hello ]; }
And then let’s test it with lorri shell
:
$ lorri shell lorri: building environment........ done (lorri) $
And let’s see if hello
is available inside the shell:
(lorri) $ hello Hello, world!
You can set environment variables inside the shell.nix
file. Do so like this:
# shell.nix let sources = import ./nix/sources.nix; pkgs = import sources.nixpkgs {}; in pkgs.mkShell { buildInputs = [ pkgs.hello ]; # Environment variables HELLO="world"; }
Wait a moment for lorri to finish rebuilding the development environment and then let’s see if the environment variable shows up:
$ cd . direnv: loading ~/code/helloworld/.envrc <output snipped> $ echo $HELLO world
Now that we have the basics of the environment set up, lets install the Rust compiler.
Setting up the Rust compiler
First, add nixpkgs-mozilla to niv:
$ niv add mozilla/nixpkgs-mozilla
Then create nix/rust.nix
in your repo:
# nix/rust.nix { sources ? import ./sources.nix }: let pkgs = import sources.nixpkgs { overlays = [ (import sources.nixpkgs-mozilla) ]; }; channel = "nightly"; date = "2020-03-08"; targets = [ ]; chan = pkgs.rustChannelOfTargets channel date targets; in chan
This creates a nix function that takes in the pre-imported list of sources,
creates a copy of nixpkgs with Rust at the nightly version 2020-03-08
overlaid
into it, and exposes the rust package out of it. Let’s add this to shell.nix
:
# shell.nix let sources = import ./nix/sources.nix; rust = import ./nix/rust.nix { inherit sources; }; pkgs = import sources.nixpkgs { }; in pkgs.mkShell { buildInputs = [ rust ]; }
Then ask lorri to recreate the development environment. This may take a bit to run because it’s setting up everything the Rust compiler requires to run.
$ lorri shell (lorri) $
Let’s see what version of Rust is installed:
(lorri) $ rustc --version rustc 1.43.0-nightly (823ff8cf1 2020-03-07)
This is exactly what we expect. Rust nightly versions get released with the
date of the previous day in them. To be extra sure, let’s see what the shell
thinks rustc
resolves to:
(lorri) $ which rustc /nix/store/w6zk1zijfwrnjm6xyfmrgbxb6dvvn6di-rust-1.43.0-nightly-2020-03-07-823ff8cf1/bin/rustc
And now exit that shell and reload direnv:
(lorri) $ exit $ cd . direnv: loading ~/code/helloworld/.envrc $ which rustc /nix/store/w6zk1zijfwrnjm6xyfmrgbxb6dvvn6di-rust-1.43.0-nightly-2020-03-07-823ff8cf1/bin/rustc
And now we have Rust installed at an arbitrary nightly version for that project only . This will work on other machines too. Now that we have our development environment set up, let’s serve HTTP.
Serving HTTP
Rocket is a popular web framework for Rust programs. Let’s use that to create a small “hello, world” server. We will need to do the following:
cargo build
Create the new Rust project
Create the new Rust project with cargo init
:
$ cargo init --vcs git . Created binary (application) package
This will create the directory src
and a file named Cargo.toml
. Rust code
goes in src
and the Cargo.toml
file configures dependencies. Adding the --vcs git
flag also has cargo create a gitignore
file so that the
target folder isn’t tracked by git.
Add Rocket as a dependency
Open Cargo.toml
and add the following to it:
[dependencies] rocket = "0.4.3"
Then download/build Rocket with cargo build
:
$ cargo build
This will download all of the dependencies you need and precompile Rocket. This will help speed up later builds.
Write our “hello world” route
Now put the following in src/main.rs
:
#![feature(proc_macro_hygiene, decl_macro)] // language features needed by Rocket // Import the rocket macros #[macro_use] extern crate rocket; // Create route / that returns "Hello, world!" #[get("/")] fn index() -> &'static str { "Hello, world!" } fn main() { rocket::ignite().mount("/", routes![index]).launch(); }
Test a build
Rerun cargo build
:
$ cargo build
This will create the binary at target/debug/helloworld
. Let’s run it locally
and see if it works:
$ ./target/debug/helloworld & $ curl http://127.0.0.1:8000 Hello, world! $ fg <press control-c>
The HTTP service works. We have a binary that is created with the Rust compiler Nix installed.
A simple package build
Now that we have the HTTP service working, let’s put it inside a nix package. We will need to use naersk to do this. Add naersk to your project with niv:
$ niv add nmattia/naersk
Now let’s create helloworld.nix
:
# import niv sources and the pinned nixpkgs { sources ? import ./nix/sources.nix, pkgs ? import sources.nixpkgs { }}: let # import rust compiler rust = import ./nix/rust.nix { inherit sources; }; # configure naersk to use our pinned rust compiler naersk = pkgs.callPackage sources.naersk { rustc = rust; cargo = rust; }; # tell nix-build to ignore the `target` directory src = builtins.filterSource (path: type: type != "directory" || builtins.baseNameOf path != "target") ./.; in naersk.buildPackage { inherit src; remapPathPrefix = true; # remove nix store references for a smaller output package }
And then build it with nix-build
:
$ nix-build helloworld.nix
This can take a bit to run, but it will do the following things:
./result
Once it is done, let’s take a look at the result:
$ du -hs ./result/bin/helloworld 2.1M ./result/bin/helloworld $ ldd ./result/bin/helloworld linux-vdso.so.1 (0x00007fffae080000) libdl.so.2 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/libdl.so.2 (0x0 0007f3a01666000) librt.so.1 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/librt.so.1 (0x0 0007f3a0165c000) libpthread.so.0 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/libpthread .so.0 (0x00007f3a0163b000) libgcc_s.so.1 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/libgcc_s.so. 1 (0x00007f3a013f5000) libc.so.6 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/libc.so.6 (0x000 07f3a0123f000) /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/ld-linux-x86-64.so.2 => /lib6 4/ld-linux-x86-64.so.2 (0x00007f3a0160b000) libm.so.6 => /nix/store/wx1vk75bpdr65g6xwxbj4rw0pk04v5j3-glibc-2.27/lib/libm.so.6 (0x000 07f3a010a9000)
This means that the Nix build created a 2.1 megabyte binary that only depends on glibc , the implementation of the C language standard library that Nix prefers.
For repo cleanliness, add the result
link to the gitignore
:
$ echo 'result*' >> .gitignore
Shipping it in a Docker image
Now that we have a package built, let’s ship it in a docker image. nixpkgs
provides dockerTools
which helps us create docker images out of
Nix packages. Let’s create default.nix
with the following contents:
{ system ? builtins.currentSystem }: let sources = import ./nix/sources.nix; pkgs = import sources.nixpkgs { }; helloworld = import ./helloworld.nix { inherit sources pkgs; }; name = "xena/helloworld"; tag = "latest"; in pkgs.dockerTools.buildLayeredImage { inherit name tag; contents = [ helloworld ]; config = { Cmd = [ "/bin/helloworld" ]; Env = [ "ROCKET_PORT=5000" ]; WorkingDir = "/"; }; }
And then build it with nix-build
:
$ nix-build default.nix
This will create a tarball containing the docker image information as the result
of the Nix build. Load it into docker using docker load
:
$ docker load -i result
And then run it using docker run
:
$ docker run --rm -itp 52340:5000 xena/helloworld
Now test it using curl:
$ curl http://127.0.0.1:52340 Hello, world!
And now you have a docker image you can run wherever you want. The buildLayeredImage
function used in default.nix
also makes Nix put each
dependency of the package into its own docker layer. This makes new versions of
your program very efficient to upgrade on your clusters, realistically this
reduces the amount of data needed for new versions of the program down to what
changed. If nothing but some resources in their own package were changed, only
those packages get downloaded.
This is how I start a new project with Nix. I put all of the code described in this post in this GitHub repo in case it helps. Have fun and be well.
For some “extra credit” tasks, try and see if you can do the following:
- Use the version of niv that niv pinned
- Customize the environment of the container by following the Rocket configuration documentation
- Add some more routes to the program
- Read the Nix documentation and learn more about writing Nix expressions
-
Configure your editor/IDE to use the
direnv
path
This article was posted on 2020 M3 8. Facts and circumstances may have changed since publication. Pleasecontact me before jumping to conclusions if something seems wrong or unclear.
Series:howto
Tags: #nix #rust
以上所述就是小编给大家介绍的《How I Start: Nix》,希望对大家有所帮助,如果大家有任何疑问请给我留言,小编会及时回复大家的。在此也非常感谢大家对 码农网 的支持!
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