Zero downtime deployment script for ubuntu nginx server on EC2

ec2-ubuntu-nginx-deploy.sh

#!/bin/bash

set -e

die () {
    echo >&2 "$@"
    exit 1
}

reset_opcache() {
    sudo php /home/ubuntu/cachetool.phar opcache:reset --fcgi=/run/php/php7.4-fpm.sock
}

# this var has been manually set on the server. it's meant to avoid accidentally
# running this script on someone's local machine.
[ "$IS_EC2_SERVER" -eq 1 ] || die 'Refusing to run on non EC2 server'

# set vars
BUILD_PATH=/home/ubuntu/builds
LAST_SUCCESS_FILE=/home/ubuntu/.deploy_last_success
LAST_SUCCESS_BUILD=$(cat $LAST_SUCCESS_FILE)
TIMESTAMP=$(date +"%Y%m%d%H%M%S")

# if a build folder name is provided, we can revert back to it
if [ "$#" -eq 1 ]; then
    # re-install old build
    TIMESTAMP=$1
else
    # new deployments are uploaded by the CI server here: $BUILD_PATH/new
    # then we rename it to the current $TIMESTAMP.
    mv "$BUILD_PATH/new" "$BUILD_PATH/$TIMESTAMP"
fi

sudo ln -sfn "$BUILD_PATH/$TIMESTAMP" "$BUILD_PATH/current"

reset_opcache

# try the app
if [[ $(curl -sL -w "%{http_code}" 127.0.0.1 -o /dev/null) == 200 ]]; then
    # record success
    echo "$TIMESTAMP" > $LAST_SUCCESS_FILE
    echo "$TIMESTAMP built successfully"
    exit 0
else
    # revert to last successful build
    sudo ln -sfn "$BUILD_PATH/$LAST_SUCCESS_BUILD" "$BUILD_PATH/current"
    reset_opcache

    # delete bad build
    rm -rf "${BUILD_PATH:?}/$TIMESTAMP"

    die "Build failed; reverted back to $LAST_SUCCESS_BUILD"
fi