Developing and testing all components in the DendrETH projects requires a diverse set of software packages that must be installed by all contributors:
- Compilers and development libraries for the full set of supported blockchains.
- Blockchain simulation environments.
- Testing frameworks.
- Various project automation tools and utilities such as Docker Compose, tmux, etc.
If the members of the development team were required to install all these components manually, setting up the project on a new machine would have been quite tedious. Updates would be difficult to coordinate and it would be nearly impossible to ensure that everybody is using the same version of the required software which creates a lot of potential avenues for the emergence of the infamous "it works on my machine" problem.
The Nix package manager offers a principled solution for this problem by making it trivial to describe in code a fully reproducible development environment where each and every software component used during the build is pinned to a precise version.
The developers don't have to spend time coordinating upgrades because Nix can execute them as soon as the file describing the development environment is changed (naturally, this file is stored in git as part of the project tree). Besides solving the "it works on my machine" problem, this makes setting up the project on a new machine trivial.
Furthermore, Nix makes it practical to have multiple projects on a single machine that use different versions of the required tools. If the DendrETH project wants to upgrade the Rust compiler to a nightly version, this won't interfere with the build environment of any other projects where all tools can be pinned to a different version.
You can think about Nix as the "virtualenv for all software". In practice, working with multiple projects is made extremely easy by the direnv tool which can switch your environment automatically every time you enter a particular project's directory.
To install Nix on any Linux distribution or macOS, simply run the following command:
sh <(curl -L https://nixos.org/nix/install) --daemonDendrETH is taking advantage of some experimental Nix features such as the
nix command the so-called flakes, which provide more control when pinning
all dependencies of the project to precise versions. These features must be
enabled manually after the installation. To learn more about the Nix
flakes, please see the following tutorial:
https://www.tweag.io/blog/2020-05-25-flakes/
The fully-reproducible development environment of the DendrETH project is defined in the following simple file:
https://github.com/metacraft-labs/DendrETH/blob/main/shell.nix
Please note that the precise versions of the referenced packages are pinned through a lock file, also stored in the repo.
If you need further and more general introduction to development with Nix, the following article may be a good start: