Allow developers to use nix-shell to get started (#554)

* Fix: Developers needed to manually create a PostgreSQL and Redis databases

Solution: Provide a `shell.nix` file so developers can just run `nix-shell` to start temporary PostgreSQL and Redis servers.

The exit signal of the shell is `trap`-ed in order to automatically stop the services on exit.

* Fix: nix-shell did not provide Python dependencies

* Doc: Document usage of nix-shell

* Fix: There was no CI on nix-shell

* fixup! git depth

* fixup! matrix run on macos too

* fixup! bump action versions

* fixup! CI fixes

* fixup! CI fixes

* fixup! CI fixes

* fixup! CI fixes

* WIP: Try fixing greenlet on macos

* Add nix installation link

Co-authored-by: Hugo Herter <[email protected]>

---------

Co-authored-by: Mike Hukiewitz <[email protected]>

.github/workflows/nix-ci.yml

@@ -0,0 +1,31 @@
+name: Test nix-shell
+
+on:
+  push:
+    branches:
+      - '*'
+
+jobs:
+  nix-shell:
+    strategy:
+      matrix:
+        os: [ macos-latest, ubuntu-latest ]
+    runs-on: ${{ matrix.os }}
+
+    steps:
+        - uses: actions/checkout@v4
+          with:
+            # Fetch the whole history for all tags and branches (required for aleph.__version__)
+            fetch-depth: 0
+
+        - name: Setup empty config file
+          run: touch config.yml
+
+        - name: Set up Nix
+          uses: cachix/install-nix-action@v25
+          with:
+            # Use channel nixos-23.11 for Linux and nixpkgs-23.11-darwin for macOS
+            nix_path: nixpkgs=channel:${{ matrix.os == 'macos-latest' && 'nixpkgs-23.11-darwin' || 'nixos-23.11' }}
+
+        - name: Run tests
+          run: nix-shell --run "pytest"

README.md

@@ -38,6 +38,18 @@ pip install -e .[testing,docs]
 
 You're ready to go!
 
+### Developer setup using Nix
+
+We started to add Nix as an easy way to setup a development environment.
+This is still a work in progress and not all dependencies are covered yet.
+
+To use it, you need to [have Nix installed on your system](https://nixos.org/download.html). Then you can run:
+
+```bash
+nix-shell
+```
+This will provide you with a shell with PostgreSQL, Redis, and IPFS running.
+
 ## Software used
 
 The Aleph CCN is written in Python and requires Python v3.8+. It will not work with older versions of Python.

shell.nix

@@ -0,0 +1,69 @@
+{ pkgs ? import <nixpkgs> {} }:
+
+pkgs.mkShell {
+  buildInputs = [
+    pkgs.postgresql
+    pkgs.redis
+    pkgs.kubo
+
+    pkgs.python311
+    pkgs.python311Packages.virtualenv
+    pkgs.python311Packages.pip
+    pkgs.python311Packages.setuptools
+
+    pkgs.python311Packages.secp256k1
+    pkgs.python311Packages.fastecdsa
+    pkgs.python311Packages.greenlet
+  ];
+
+  shellHook = ''
+    echo "Setting up PostgreSQL environment..."
+    export PGDATA=$(mktemp -d)
+    PG_SOCKET_DIR=$(mktemp -d)
+    echo "Initializing database..."
+    initdb $PGDATA
+
+    echo "Starting PostgreSQL with custom socket directory..."
+    pg_ctl -D $PGDATA -o "-k $PG_SOCKET_DIR" -l logfile start
+
+    # Wait a bit for the server to start
+    sleep 1
+
+    # Create the 'aleph' role and a database
+    createuser -h $PG_SOCKET_DIR aleph
+    createdb -h $PG_SOCKET_DIR aleph -O aleph
+
+    # Create a temporary directory for Redis
+    export REDIS_DATA_DIR=$(mktemp -d)
+    redis-server --daemonize yes --dir $REDIS_DATA_DIR --bind 127.0.0.1 --port 6379
+    echo "Redis server started. Data directory is $REDIS_DATA_DIR"
+
+    echo "Starting IPFS Kubo..."
+    export IPFS_PATH=$(mktemp -d)
+    ipfs init
+    ipfs daemon &
+    echo "IPFS Kubo started. Data directory is $IPFS_PATH"
+
+    echo
+    echo "PostgreSQL started. Data directory is $PGDATA, Socket directory is $PG_SOCKET_DIR"
+    echo "Redis started. Data directory is $REDIS_DATA_DIR"
+    echo "Use 'psql -h $PG_SOCKET_DIR' to connect to the database."
+    echo "Use 'redis-cli -p 6379' to connect to the Redis server."
+    echo "To stop PostgreSQL: 'pg_ctl -D $PGDATA stop'"
+    echo "To manually stop Redis: 'redis-cli -p 6379 shutdown'"
+
+    # Trap the EXIT signal to stop services when exiting the shell
+    trap 'echo "Stopping PostgreSQL..."; pg_ctl -D "$PGDATA" stop; echo "Stopping Redis..."; redis-cli -p 6379 shutdown; echo "Stopping IPFS Kubo..."; ipfs shutdown; deactivate' EXIT
+
+    # Create a virtual environment in the current directory if it doesn't exist
+    if [ ! -d "venv" ]; then
+      python3 -m virtualenv venv
+    fi
+
+    # Install the required Python packages
+    ./venv/bin/pip install -e .\[testing\]
+
+    # Activate the virtual environment
+    source venv/bin/activate
+  '';
+}