deploy.sh

#!/bin/bash
set -e

# Update to latest version of code
cd /home/<YOUR_USERNAME>/my_app
git fetch
git reset --hard origin/main
mix deps.get --only prod

# Optional CI steps
CI=true mix test
# mix credo --strict (commented out, just another example step)

# Set mix_env so subsequent mix steps don't need to specify it
export MIX_ENV=prod

# Build phase
mix assets.deploy

# Identify the currently running release
current_release=$(ls ../releases | sort -nr | head -n 1)
now_in_unix_seconds=$(date +'%s')
if [[ $current_release == '' ]]; then current_release=$now_in_unix_seconds; fi

# Create release
mix release --path ../releases/${now_in_unix_seconds}

# Get the HTTP_PORT variable from the currently running release
source ../releases/${current_release}/releases/0.1.0/env.sh

if [[ $HTTP_PORT == '4000' ]]
then
  http=4001
  https=4041
  old_port=4000
else
  http=4000
  https=4040
  old_port=4001
fi

# Put env vars with the ports to forward to, and set non-conflicting node name
echo "export HTTP_PORT=${http}" >> ../releases/${now_in_unix_seconds}/releases/0.1.0/env.sh
echo "export HTTPS_PORT=${https}" >> ../releases/${now_in_unix_seconds}/releases/0.1.0/env.sh
echo "export RELEASE_NAME=${http}" >> ../releases/${now_in_unix_seconds}/releases/0.1.0/env.sh

# Set the release to the new version
rm ../env_vars || true
touch ../env_vars
echo "RELEASE=${now_in_unix_seconds}" >> ../env_vars

# Run migrations
mix ecto.migrate

# Boot the new version of the app
sudo systemctl start my_app@${http}

# Wait for the new version to boot
until $(curl --output /dev/null --silent --head --fail localhost:${http}); do
  echo 'Waiting for app to boot...'
  sleep 1
done

# Switch forwarding of ports 443 and 80 to the ones the new app is listening on
sudo iptables -t nat -R PREROUTING 1 -p tcp --dport 80 -j REDIRECT --to-port ${http}
sudo iptables -t nat -R PREROUTING 2 -p tcp --dport 443 -j REDIRECT --to-port ${https}

# Stop the old version
sudo systemctl stop my_app@${old_port}

# Just in case the old version was started by systemd after a server
# reboot, also stop the server_reboot version
sudo systemctl stop my_app@server_reboot

echo 'Deployed!'