Socket Activation systemd service with Unicorn & Nginx

config.ru

require 'bundler/setup'
Bundler.require

require 'rack'

app = Proc.new do |env|
  ['200', {'Content-Type' => 'text/html'}, ['Simple app for test']]
end

run app

Dockerfile

FROM ruby:2.4
RUN mkdir /app
COPY Gemfile Gemfile.lock /app/
WORKDIR /app
RUN bundle install
ADD config.ru /app/
ADD unicorn.rb /app/
CMD ["bundle", "exec", "--keep-file-descriptors", "unicorn", "-c", "unicorn.rb"]

Gemfile

source 'https://rubygems.org'

gem 'unicorn'
gem 'rack'

Gemfile.lock

GEM
  remote: https://rubygems.org/
  specs:
    kgio (2.11.2)
    rack (2.0.5)
    raindrops (0.19.0)
    unicorn (5.4.0)
      kgio (~> 2.6)
      raindrops (~> 0.7)

PLATFORMS
  ruby

DEPENDENCIES
  rack
  unicorn

BUNDLED WITH
   1.16.1

sact-test-docker.service

[Unit]
Description=Socket Activation with Unicorn Service
After=network.target sact-test.socket
Requires=sact-test.socket

[Service]
ExecStart=/usr/bin/docker run --user 1001 --rm --name sact-test-n -v '/apps/sact/sact-git/tmp:/app/tmp' -e 'SOCKET_FILE=/app/tmp/sockets/unicorn.sock' sact-test
ExecStartPost=/bin/sleep 1
SyslogIdentifier=sact-test-docker
ExecStop=/usr/bin/docker stop sact-test-n

sact-test.service

[Unit]
Requires=sact-test-docker.service
After=sact-test-docker.service

[Service]
SyslogIdentifier=sact-test-docker
ExecStart=/lib/systemd/systemd-socket-proxyd /apps/sact/sact-git/tmp/sockets/unicorn.sock

sact-test.socket

[Unit]
Description=Socket Activation with Unicorn
PartOf=sact-test.service

[Socket]
SocketUser=sact
SocketGroup=sact
SocketMode=0777
Backlog=2048
ListenStream=/apps/sact/sact-git/tmp/sockets/unicorn-proxy.sock

[Install]
WantedBy=sockets.target

sact.conf

upstream app_sact {
    server unix:/apps/sact/sact-git/tmp/sockets/unicorn-proxy.sock;
}

server {
  listen 80;
  charset utf-8;
  set $application_name "sact";

  location / {
    try_files $uri $uri.html @application;
  }

    location @application {
        proxy_set_header Host $host;
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_hide_header X-User-Id;

        proxy_redirect off;
        proxy_pass http://app_$application_name;
        break;
    }
}

unicorn.rb

worker_processes 2
timeout 30
listen ENV['SOCKET_FILE'] || 8080, backlog: 2048
working_directory ENV['APP_PATH'] || '/app/'