I use these batch script to achieve Zero-deployment for phoenix application with releases without docker.

build_release.sh

#!/bin/bash

# Exit immediately if a command exits with a non-zero status
set -e

SCRIPT_PATH=$(dirname "$(realpath "$0")")
BUILD_PATH=$SCRIPT_PATH"/.."

# Change directory to build path
cd $BUILD_PATH

# Function to display an error and exit
function error_exit {
  echo "Error: $1"
  exit 1
}

# Step 1: Fetch production dependencies
echo "1. Fetching production dependencies..."
mix deps.get --only prod || error_exit "Failed to fetch dependencies."

# Step 2: Compile the application in production environment
echo "2. Compiling the application for production..."
MIX_ENV=prod mix compile || error_exit "Compilation failed."

# Step 3: Deploy assets
echo "3. Deploying assets..."
# setopt rm_star_silent  # Disable prompt for delete confirmation
# Remove previously compiled assets
rm -rf priv/static/*

MIX_ENV=prod mix assets.deploy || error_exit "Asset deployment failed."

# Step 4: Generate the release
echo "Generating the Phoenix release..."
mix phx.gen.release || error_exit "Failed to generate the Phoenix release."

# Step 5: Build the release
echo "Building the release..."
yes | MIX_ENV=prod mix release || error_exit "Release build failed."

echo "Release build completed successfully!"

Caddyfile

your-domain.com {
	reverse_proxy localhost:4010 localhost:4020 localhost:4030 localhost:4040 localhost:4050 localhost:4060
}

deploy.sh

#!/bin/bash

# Initialize variables
PORTS=("4010" "4020" "4030" "4040" "4050" "4060") # Default ports for zero-downtime deployment
USERNAME="postgres"
PASSWORD="ikijumba"
HOST="localhost"
DATABASE="hr_dev"
APP_NAME="hr"
MODE="daemon_iex"

# It's important for this to be static. It will be needed to restart apps/ releases.
SECRET_KEY="J1k3ARebfz5+zTGI5Uc4Z4gy6F6XxCJXN3V10dNiOIP1joQcExncj9JsQeQcsaYg"

SCRIPT_PATH=$(dirname "$(realpath "$0")")
BUILD_PATH="/home/kamaro/elixir/hr/_build/prod/rel/hr"

# Change directory to build path
cd $BUILD_PATH

# Change to the directory with the app for release
cd $BUILD_PATH

# Parse named parameters
while [[ $# -gt 0 ]]; do
  case $1 in
    --ports)
      IFS=',' read -ra PORTS <<< "$2" # Split comma-separated ports into an array
      shift 2
      ;;
    --username)
      USERNAME=$2
      shift 2
      ;;
    --password)
      PASSWORD=$2
      shift 2
      ;;
    --host)
      HOST=$2
      shift 2
      ;;
    --database)
      DATABASE=$2
      shift 2
      ;;
    --app-name)
      APP_NAME=$2
      shift 2
      ;;
    --build-path)
      BUILD_PATH=$2
      shift 2
      ;;
    --secret-key)
      SECRET_KEY=$2
      shift 2
      ;;
    --mode)
      MODE=$2
      shift 2
      ;;
    *)
      echo "Unknown option: $1"
      exit 1
      ;;
  esac
done

# Check if all required parameters are provided
if [ -z "$PORTS" ] || [ -z "$USERNAME" ] || [ -z "$PASSWORD" ] || [ -z "$HOST" ] || [ -z "$DATABASE" ] || [ -z "$APP_NAME" ] || [ -z "$BUILD_PATH" ] || [ -z "$SECRET_KEY" ]; then
  echo "Error: Missing required parameters."
  echo "Usage: $0 --ports <port1,port2,...> --username <username> --password <password> --host <host> --database <database> --app-name <app_name> --build-path <build_path> --secret-key <secret_key>"
  exit 1
fi

# Export required environment variables
export SECRET_KEY_BASE=$SECRET_KEY
export DATABASE_URL=ecto://$USERNAME:$PASSWORD@$HOST/$DATABASE

# Function to check if a port is responding
function is_port_responding() {
  local PORT=$1
  for i in {1..30}; do
    if nc -z localhost $PORT; then
      echo "Port $PORT is responding!"
      return 0
    fi
    echo "Waiting for port $PORT to respond... (attempt $i)"
    sleep 1
  done
  echo "Port $PORT did not respond in time."
  return 1
}

# To Achieve Zero-downtime deployment, we need to have multiple instances of the same application on different port, then 
# restart them in sequences. Since caddy is handling reverse proxy/ load balancing, it will automatically respond to the 
# available port. See card configurations.
for PORT in "${PORTS[@]}"; do
    echo "Stopping existing app_$PORT on port $PORT (if running)..."
    RELEASE_NODE=app_$PORT PORT=$PORT $BUILD_PATH/bin/$APP_NAME stop || echo "No running instance on port $PORT"

    echo "Restarting app_$PORT on port $PORT..."
    RELEASE_NODE=app_$PORT PORT=$PORT $BUILD_PATH/bin/$APP_NAME daemon

    echo "Checking if instance on port $PORT is responding..."
    if ! is_port_responding $PORT; then
        echo "Failed to start app_$PORT on port $PORT Aborting."
        exit 1
    fi
done

echo "Zero-downtime deployment complete. Running on ports: ${PORTS[*]}"

ship_to_production.sh

#!/bin/bash 

SCRIPT_PATH=$(dirname "$(realpath "$0")")
BUILD_PATH=$SCRIPT_PATH"/.."
PRODUCTION_SERVER_HOST="SERVER_IP_ADDRESS"
PRODUCTION_USER="root"
APP_ENV="prod"
APP_NAME="hr"

echo "1. Zipping release into $APP_NAME.tar.gz..."
tar -czf $APP_NAME.tar.gz -C  $BUILD_PATH/_build/${APP_ENV}/rel/$APP_NAME .

echo "2. Moving $APP_NAME.tar.gz to production server..."
scp  $APP_NAME.tar.gz $PRODUCTION_USER@$PRODUCTION_SERVER_HOST:~/