Add experimental support for Puma

This allows us (and others) to test drive Puma without it affecting all
users. Puma can be enabled by setting the environment variable
"EXPERIMENTAL_PUMA" to a non empty value.

.gitignore

@@ -40,6 +40,7 @@ eslint-report.html
 /config/redis.queues.yml
 /config/redis.shared_state.yml
 /config/unicorn.rb
+/config/puma.rb
 /config/secrets.yml
 /config/sidekiq.yml
 /config/registry.key

Gemfile

@@ -153,6 +153,11 @@ group :unicorn do
   gem 'unicorn-worker-killer', '~> 0.4.4'
 end
 
+group :puma do
+  gem 'puma', '~> 3.12', require: false
+  gem 'puma_worker_killer', require: false
+end
+
 # State machine
 gem 'state_machines-activerecord', '~> 0.5.1'
 

Gemfile.lock

@@ -598,6 +598,10 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.3)
+    puma (3.12.0)
+    puma_worker_killer (0.1.0)
+      get_process_mem (~> 0.2)
+      puma (>= 2.7, < 4)
     pyu-ruby-sasl (0.0.3.3)
     rack (1.6.10)
     rack-accept (0.4.5)
@@ -1076,6 +1080,8 @@ DEPENDENCIES
   prometheus-client-mmap (~> 0.9.4)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
+  puma (~> 3.12)
+  puma_worker_killer
   rack-attack (~> 4.4.1)
   rack-cors (~> 1.0.0)
   rack-oauth2 (~> 1.2.1)

Gemfile.rails5.lock

@@ -602,6 +602,10 @@ GEM
     pry-rails (0.3.6)
       pry (>= 0.10.4)
     public_suffix (3.0.3)
+    puma (3.12.0)
+    puma_worker_killer (0.1.0)
+      get_process_mem (~> 0.2)
+      puma (>= 2.7, < 4)
     pyu-ruby-sasl (0.0.3.3)
     rack (2.0.5)
     rack-accept (0.4.5)
@@ -1085,6 +1089,8 @@ DEPENDENCIES
   prometheus-client-mmap (~> 0.9.4)
   pry-byebug (~> 3.4.1)
   pry-rails (~> 0.3.4)
+  puma (~> 3.12)
+  puma_worker_killer
   rack-attack (~> 4.4.1)
   rack-cors (~> 1.0.0)
   rack-oauth2 (~> 1.2.1)

bin/web

@@ -3,6 +3,11 @@
 cd $(dirname $0)/..
 app_root=$(pwd)
 
+# Switch to experimental PUMA configuration
+if [ -n "${EXPERIMENTAL_PUMA}" ]; then
+  exec bin/web_puma "$@"
+fi
+
 unicorn_pidfile="$app_root/tmp/pids/unicorn.pid"
 unicorn_config="$app_root/config/unicorn.rb"
 unicorn_cmd="bundle exec unicorn_rails -c $unicorn_config -E $RAILS_ENV"

bin/web_puma

+#!/bin/sh
+
+set -e
+
+cd $(dirname $0)/..
+app_root=$(pwd)
+
+puma_pidfile="$app_root/tmp/pids/puma.pid"
+puma_config="$app_root/config/puma.rb"
+
+spawn_puma()
+{
+  exec bundle exec puma --config "${puma_config}" "$@"
+}
+
+get_puma_pid()
+{
+  pid=$(cat "${puma_pidfile}")
+  if [ -z "$pid" ] ; then
+    echo "Could not find a PID in $puma_pidfile"
+    exit 1
+  fi
+  echo "${pid}"
+}
+
+start()
+{
+  spawn_puma -d
+}
+
+start_foreground()
+{
+  spawn_puma
+}
+
+stop()
+{
+  get_puma_pid
+  kill -QUIT "$(get_puma_pid)"
+}
+
+reload()
+{
+  kill -USR2 "$(get_puma_pid)"
+}
+
+case "$1" in
+  start)
+    start
+    ;;
+  start_foreground)
+    start_foreground
+    ;;
+  stop)
+    stop
+    ;;
+  reload)
+    reload
+    ;;
+  *)
+    echo "Usage: RAILS_ENV=your_env $0 {start|stop|reload}"
+    ;;
+esac

changelogs/unreleased/an-multithreading.yml

+---
+title: Experimental support for running Puma multithreaded web-server
+merge_request: 22372
+author:
+type: performance

config/initializers/7_prometheus_metrics.rb

@@ -26,9 +26,25 @@ Sidekiq.configure_server do |config|
 end
 
 if !Rails.env.test? && Gitlab::Metrics.prometheus_metrics_enabled?
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    defined?(::Prometheus::Client.reinitialize_on_pid_change) && Prometheus::Client.reinitialize_on_pid_change
+
     unless Sidekiq.server?
       Gitlab::Metrics::Samplers::UnicornSampler.initialize_instance(Settings.monitoring.unicorn_sampler_interval).start
     end
 
     Gitlab::Metrics::Samplers::RubySampler.initialize_instance(Settings.monitoring.ruby_sampler_interval).start
+  end
+end
+
+Gitlab::Cluster::LifecycleEvents.on_master_restart do
+  # The following is necessary to ensure stale Prometheus metrics don't
+  # accumulate over time. It needs to be done in this hook as opposed to
+  # inside an init script to ensure metrics files aren't deleted after new
+  # unicorn workers start after a SIGUSR2 is received.
+  prometheus_multiproc_dir = ENV['prometheus_multiproc_dir']
+  if prometheus_multiproc_dir
+    old_metrics = Dir[File.join(prometheus_multiproc_dir, '*.db')]
+    FileUtils.rm_rf(old_metrics)
+  end
 end

config/initializers/8_metrics.rb

@@ -158,7 +158,9 @@ if Gitlab::Metrics.enabled? && !Rails.env.test?
 
   GC::Profiler.enable
 
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
     Gitlab::Metrics::Samplers::InfluxSampler.initialize_instance.start
+  end
 
   module TrackNewRedisConnections
     def connect(*args)

config/initializers/active_record_lifecycle.rb

+# frozen_string_literal: true
+
+# Don't handle sidekiq configuration as it
+# has its own special active record configuration here
+if defined?(ActiveRecord::Base) && !Sidekiq.server?
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    ActiveSupport.on_load(:active_record) do
+      ActiveRecord::Base.establish_connection
+
+      Rails.logger.debug("ActiveRecord connection established")
+    end
+  end
+end
+
+if defined?(ActiveRecord::Base)
+  Gitlab::Cluster::LifecycleEvents.on_before_fork do
+    # the following is highly recommended for Rails + "preload_app true"
+    # as there's no need for the master process to hold a connection
+    ActiveRecord::Base.connection.disconnect!
+
+    Rails.logger.debug("ActiveRecord connection disconnected")
+  end
+end

config/initializers/macos.rb

+# frozen_string_literal: true
+
+if /darwin/ =~ RUBY_PLATFORM
+  Gitlab::Cluster::LifecycleEvents.on_before_fork do
+    require 'fiddle'
+
+    # Dynamically load Foundation.framework, ~implicitly~ initialising
+    # the Objective-C runtime before any forking happens in Unicorn
+    #
+    # From https://bugs.ruby-lang.org/issues/14009
+    Fiddle.dlopen '/System/Library/Frameworks/Foundation.framework/Foundation'
+  end
+end

config/initializers/rbtrace.rb

+# frozen_string_literal: true
+
+if ENV['ENABLE_RBTRACE']
+  Gitlab::Cluster::LifecycleEvents.on_worker_start do
+    # Unicorn clears out signals before it forks, so rbtrace won't work
+    # unless it is enabled after the fork.
+    require 'rbtrace'
+  end
+end

config/initializers/sidekiq.rb

@@ -14,8 +14,6 @@ Sidekiq.default_worker_options = { retry: 3 }
 enable_json_logs = Gitlab.config.sidekiq.log_format == 'json'
 
 Sidekiq.configure_server do |config|
-  require 'rbtrace' if ENV['ENABLE_RBTRACE']
-
   config.redis = queues_config_hash
 
   config.server_middleware do |chain|

config/puma.example.development.rb

+# frozen_string_literal: true
+
+# -----------------------------------------------------------------------
+# This file is used by the GDK to generate a default config/puma.rb file
+# Note that `/home/git` will be substituted for the actual GDK root
+# directory when this file is generated
+# -----------------------------------------------------------------------
+
+# Load "path" as a rackup file.
+#
+# The default is "config.ru".
+#
+rackup 'config.ru'
+pidfile '/home/git/gitlab/tmp/pids/puma.pid'
+state_path '/home/git/gitlab/tmp/pids/puma.state'
+
+stdout_redirect '/home/git/gitlab/log/puma.stdout.log',
+  '/home/git/gitlab/log/puma.stderr.log',
+  true
+
+# Configure "min" to be the minimum number of threads to use to answer
+# requests and "max" the maximum.
+#
+# The default is "0, 16".
+#
+threads 1, 4
+
+# By default, workers accept all requests and queue them to pass to handlers.
+# When false, workers accept the number of simultaneous requests configured.
+#
+# Queueing requests generally improves performance, but can cause deadlocks if
+# the app is waiting on a request to itself. See https://github.com/puma/puma/issues/612
+#
+# When set to false this may require a reverse proxy to handle slow clients and
+# queue requests before they reach puma. This is due to disabling HTTP keepalive
+queue_requests false
+
+# Bind the server to "url". "tcp://", "unix://" and "ssl://" are the only
+# accepted protocols.
+bind 'unix:///home/git/gitlab.socket'
+
+workers 2
+
+require_relative "/home/git/gitlab/lib/gitlab/cluster/lifecycle_events"
+require_relative "/home/git/gitlab/lib/gitlab/cluster/puma_worker_killer_initializer"
+
+on_restart do
+  # Signal application hooks that we're about to restart
+  Gitlab::Cluster::LifecycleEvents.do_master_restart
+end
+
+before_fork do
+  # Signal to the puma killer
+  Gitlab::Cluster::PumaWorkerKillerInitializer.start @config.options unless ENV['DISABLE_PUMA_WORKER_KILLER']
+
+  # Signal application hooks that we're about to fork
+  Gitlab::Cluster::LifecycleEvents.do_before_fork
+end
+
+Gitlab::Cluster::LifecycleEvents.set_puma_options @config.options
+on_worker_boot do
+  # Signal application hooks of worker start
+  Gitlab::Cluster::LifecycleEvents.do_worker_start
+end
+
+# Preload the application before starting the workers; this conflicts with
+# phased restart feature. (off by default)
+
+preload_app!
+
+tag 'gitlab-puma-worker'
+
+# Verifies that all workers have checked in to the master process within
+# the given timeout. If not the worker process will be restarted. Default
+# value is 60 seconds.
+#
+worker_timeout 60

config/unicorn.rb.example

@@ -81,22 +81,16 @@ preload_app true
 # fast LAN.
 check_client_connection false
 
+require_relative "/home/git/gitlab/lib/gitlab/cluster/lifecycle_events"
+
 before_exec do |server|
-  # The following is necessary to ensure stale Prometheus metrics don't
-  # accumulate over time. It needs to be done in this hook as opposed to
-  # inside an init script to ensure metrics files aren't deleted after new
-  # unicorn workers start after a SIGUSR2 is received.
-  if ENV['prometheus_multiproc_dir']
-    old_metrics = Dir[File.join(ENV['prometheus_multiproc_dir'], '*.db')]
-    FileUtils.rm_rf(old_metrics)
-  end
+  # Signal application hooks that we're about to restart
+  Gitlab::Cluster::LifecycleEvents.do_master_restart
 end
 
 before_fork do |server, worker|
-  # the following is highly recommended for Rails + "preload_app true"
-  # as there's no need for the master process to hold a connection
-  defined?(ActiveRecord::Base) &&
-    ActiveRecord::Base.connection.disconnect!
+  # Signal application hooks that we're about to fork
+  Gitlab::Cluster::LifecycleEvents.do_before_fork
 
   # The following is only recommended for memory/DB-constrained
   # installations.  It is not needed if your system can house
@@ -124,25 +118,10 @@ before_fork do |server, worker|
 end
 
 after_fork do |server, worker|
-  # Unicorn clears out signals before it forks, so rbtrace won't work
-  # unless it is enabled after the fork.
-  require 'rbtrace' if ENV['ENABLE_RBTRACE']
+  # Signal application hooks of worker start
+  Gitlab::Cluster::LifecycleEvents.do_worker_start
 
   # per-process listener ports for debugging/admin/migrations
   # addr = "127.0.0.1:#{9293 + worker.nr}"
   # server.listen(addr, :tries => -1, :delay => 5, :tcp_nopush => true)
-
-  # the following is *required* for Rails + "preload_app true",
-  defined?(ActiveRecord::Base) &&
-    ActiveRecord::Base.establish_connection
-
-  # reset prometheus client, this will cause any opened metrics files to be closed
-  defined?(::Prometheus::Client.reinitialize_on_pid_change) &&
-    Prometheus::Client.reinitialize_on_pid_change
-
-  # if preload_app is true, then you may also want to check and
-  # restart any other shared sockets/descriptors such as Memcached,
-  # and Redis.  TokyoCabinet file handles are safe to reuse
-  # between any number of forked children (assuming your kernel
-  # correctly implements pread()/pwrite() system calls)
 end

config/unicorn.rb.example.development

+# frozen_string_literal: true
+
+# -------------------------------------------------------------------------
+# This file is used by the GDK to generate a default config/unicorn.rb file
+# Note that `/home/git` will be substituted for the actual GDK root
+# directory when this file is generated
+# -------------------------------------------------------------------------
+
 worker_processes 2
 timeout 60
 
+listen '/home/git/gitlab.socket'
+
 preload_app true
 check_client_connection false
 
-before_fork do |server, worker|
-  # the following is highly recommended for Rails + "preload_app true"
-  # as there's no need for the master process to hold a connection
-  defined?(ActiveRecord::Base) &&
-    ActiveRecord::Base.connection.disconnect!
+require_relative "/home/git/gitlab/lib/gitlab/cluster/lifecycle_events"
+
+before_exec do |server|
+  # Signal application hooks that we're about to restart
+  Gitlab::Cluster::LifecycleEvents.do_master_restart
+end
 
-  if /darwin/ =~ RUBY_PLATFORM
-    require 'fiddle'
+before_fork do |server, worker|
+  # Signal application hooks that we're about to fork
+  Gitlab::Cluster::LifecycleEvents.do_before_fork
 
-    # Dynamically load Foundation.framework, ~implicitly~ initialising
-    # the Objective-C runtime before any forking happens in Unicorn
+  # The following is only recommended for memory/DB-constrained
+  # installations.  It is not needed if your system can house
+  # twice as many worker_processes as you have configured.
   #
-    # From https://bugs.ruby-lang.org/issues/14009
-    Fiddle.dlopen '/System/Library/Frameworks/Foundation.framework/Foundation'
+  # This allows a new master process to incrementally
+  # phase out the old master process with SIGTTOU to avoid a
+  # thundering herd (especially in the "preload_app false" case)
+  # when doing a transparent upgrade.  The last worker spawned
+  # will then kill off the old master process with a SIGQUIT.
+  old_pid = "#{server.config[:pid]}.oldbin"
+  if old_pid != server.pid
+    begin
+      sig = (worker.nr + 1) >= server.worker_processes ? :QUIT : :TTOU
+      Process.kill(sig, File.read(old_pid).to_i)
+    rescue Errno::ENOENT, Errno::ESRCH
+    end
   end
+  #
+  # Throttle the master from forking too quickly by sleeping.  Due
+  # to the implementation of standard Unix signal handlers, this
+  # helps (but does not completely) prevent identical, repeated signals
+  # from being lost when the receiving process is busy.
+  # sleep 1
 end
 
 after_fork do |server, worker|
-  # Unicorn clears out signals before it forks, so rbtrace won't work
-  # unless it is enabled after the fork.
-  require 'rbtrace' if ENV['ENABLE_RBTRACE']
+  # Signal application hooks of worker start
+  Gitlab::Cluster::LifecycleEvents.do_worker_start
 
-  # the following is *required* for Rails + "preload_app true",
-  defined?(ActiveRecord::Base) &&
-    ActiveRecord::Base.establish_connection
+  # per-process listener ports for debugging/admin/migrations
+  # addr = "127.0.0.1:#{9293 + worker.nr}"
+  # server.listen(addr, :tries => -1, :delay => 5, :tcp_nopush => true)
 end
+

lib/gitlab/cluster/lifecycle_events.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Cluster
+    #
+    # LifecycleEvents lets Rails initializers register application startup hooks
+    # that are sensitive to forking. For example, to defer the creation of
+    # watchdog threads. This lets us abstract away the Unix process
+    # lifecycles of Unicorn, Sidekiq, Puma, Puma Cluster, etc.
+    #
+    # We have three lifecycle events.
+    #
+    # - before_fork (only in forking processes)
+    # - worker_start
+    # - before_master_restart (only in forking processes)
+    #
+    # Blocks will be executed in the order in which they are registered.
+    #
+    class LifecycleEvents
+      class << self
+        #
+        # Hook registration methods (called from initializers)
+        #
+        def on_worker_start(&block)
+          if in_clustered_environment?
+            # Defer block execution
+            (@worker_start_hooks ||= []) << block
+          else
+            yield
+          end
+        end
+
+        def on_before_fork(&block)
+          return unless in_clustered_environment?
+
+          # Defer block execution
+          (@before_fork_hooks ||= []) << block
+        end
+
+        def on_master_restart(&block)
+          return unless in_clustered_environment?
+
+          # Defer block execution
+          (@master_restart_hooks ||= []) << block
+        end
+
+        #
+        # Lifecycle integration methods (called from unicorn.rb, puma.rb, etc.)
+        #
+        def do_worker_start
+          @worker_start_hooks&.each do |block|
+            block.call
+          end
+        end
+
+        def do_before_fork
+          @before_fork_hooks&.each do |block|
+            block.call
+          end
+        end
+
+        def do_master_restart
+          @master_restart_hooks && @master_restart_hooks.each do |block|
+            block.call
+          end
+        end
+
+        # Puma doesn't use singletons (which is good) but
+        # this means we need to pass through whether the
+        # puma server is running in single mode or cluster mode
+        def set_puma_options(options)
+          @puma_options = options
+        end
+
+        private
+
+        def in_clustered_environment?
+          # Sidekiq doesn't fork
+          return false if Sidekiq.server?
+
+          # Unicorn always forks
+          return true if defined?(::Unicorn)
+
+          # Puma sometimes forks
+          return true if in_clustered_puma?
+
+          # Default assumption is that we don't fork
+          false
+        end
+
+        def in_clustered_puma?
+          return false unless defined?(::Puma)
+
+          @puma_options && @puma_options[:workers] && @puma_options[:workers] > 0
+        end
+      end
+    end
+  end
+end

lib/gitlab/cluster/puma_worker_killer_initializer.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Cluster
+    class PumaWorkerKillerInitializer
+      def self.start(puma_options, puma_per_worker_max_memory_mb: 650)
+        require 'puma_worker_killer'
+
+        PumaWorkerKiller.config do |config|
+          # Note! ram is expressed in megabytes (whereas GITLAB_UNICORN_MEMORY_MAX is in bytes)
+          # Importantly RAM is for _all_workers (ie, the cluster),
+          # not each worker as is the case with GITLAB_UNICORN_MEMORY_MAX
+          worker_count = puma_options[:workers] || 1
+          config.ram = worker_count * puma_per_worker_max_memory_mb
+
+          config.frequency = 20 # seconds
+
+          # We just want to limit to a fixed maximum, unrelated to the total amount
+          # of available RAM.
+          config.percent_usage = 0.98
+
+          # Ideally we'll never hit the maximum amount of memory. If so the worker
+          # is restarted already, thus periodically restarting workers shouldn't be
+          # needed.
+          config.rolling_restart_frequency = false
+        end
+
+        PumaWorkerKiller.start
+      end
+    end
+  end
+end

spec/rack_servers/configs/config.ru

+# frozen_string_literal: true
+
+app = proc do |env|
+  if env['REQUEST_METHOD'] == 'GET'
+    [200, {}, ["#{Process.pid}"]]
+  else
+    Process.kill(env['QUERY_STRING'], Process.pid)
+    [200, {}, ['Bye!']]
+  end
+end
+
+run app

spec/rack_servers/configs/puma.rb

+# frozen_string_literal: true
+
+# Note: this file is used for testing puma in `spec/rack_servers/puma_spec.rb` only
+# Note: as per the convention in `config/puma.example.development.rb`,
+# this file will replace `/home/git` with the actual working directory
+
+directory '/home/git'
+threads 1, 10
+queue_requests false
+pidfile '/home/git/gitlab/tmp/pids/puma.pid'
+bind 'unix:///home/git/gitlab/tmp/tests/puma.socket'
+workers 1
+preload_app!
+worker_timeout 60
+
+require_relative "/home/git/gitlab/lib/gitlab/cluster/lifecycle_events"
+require_relative "/home/git/gitlab/lib/gitlab/cluster/puma_worker_killer_initializer"
+
+before_fork do
+  Gitlab::Cluster::PumaWorkerKillerInitializer.start @config.options
+  Gitlab::Cluster::LifecycleEvents.do_before_fork
+end
+
+Gitlab::Cluster::LifecycleEvents.set_puma_options @config.options
+on_worker_boot do
+  Gitlab::Cluster::LifecycleEvents.do_worker_start
+  File.write('/home/git/gitlab/tmp/tests/puma-worker-ready', Process.pid)
+end
+
+on_restart do
+  Gitlab::Cluster::LifecycleEvents.do_master_restart
+end

spec/rack_servers/puma_spec.rb

+# frozen_string_literal: true
+
+require 'fileutils'
+
+require 'excon'
+
+require 'spec_helper'
+
+describe 'Puma' do
+  before(:all) do
+    project_root = File.expand_path('../..', __dir__)
+
+    config_lines = File.read('spec/rack_servers/configs/puma.rb')
+      .gsub('/home/git/gitlab', project_root)
+      .gsub('/home/git', project_root)
+
+    config_path = File.join(project_root, "tmp/tests/puma.rb")
+    @socket_path = File.join(project_root, 'tmp/tests/puma.socket')
+
+    File.write(config_path, config_lines)
+
+    cmd = %W[puma -e test -C #{config_path} #{File.join(__dir__, 'configs/config.ru')}]
+    @puma_master_pid = spawn(*cmd)
+    wait_puma_boot!(@puma_master_pid, File.join(project_root, 'tmp/tests/puma-worker-ready'))
+    WebMock.allow_net_connect!
+  end
+
+  %w[SIGQUIT SIGTERM SIGKILL].each do |signal|
+    it "has a worker that self-terminates on signal #{signal}" do
+      response = Excon.get('unix://', socket: @socket_path)
+      expect(response.status).to eq(200)
+
+      worker_pid = response.body.to_i
+      expect(worker_pid).to be > 0
+
+      begin
+        Excon.post("unix://?#{signal}", socket: @socket_path)
+      rescue Excon::Error::Socket
+        # The connection may be closed abruptly
+      end
+
+      expect(pid_gone?(worker_pid)).to eq(true)
+    end
+  end
+
+  after(:all) do
+    begin
+      WebMock.disable_net_connect!(allow_localhost: true)
+      Process.kill('TERM', @puma_master_pid)
+    rescue Errno::ESRCH
+    end
+  end
+
+  def wait_puma_boot!(master_pid, ready_file)
+    # We have seen the boot timeout after 2 minutes in CI so let's set it to 5 minutes.
+    timeout = 5 * 60
+    timeout.times do
+      return if File.exist?(ready_file)
+
+      pid = Process.waitpid(master_pid, Process::WNOHANG)
+      raise "puma failed to boot: #{$?}" unless pid.nil?
+
+      sleep 1
+    end
+
+    raise "puma boot timed out after #{timeout} seconds"
+  end
+
+  def pid_gone?(pid)
+    # Worker termination should take less than a second. That makes 10
+    # seconds a generous timeout.
+    10.times do
+      begin
+        Process.kill(0, pid)
+      rescue Errno::ESRCH
+        return true
+      end
+
+      sleep 1
+    end
+
+    false
+  end
+end

spec/unicorn/unicorn_spec.rb → spec/rack_servers/unicorn_spec.rb

+# frozen_string_literal: true
+
 require 'fileutils'
 
 require 'excon'
@@ -6,12 +8,16 @@ require 'spec_helper'
 
 describe 'Unicorn' do
   before(:all) do
-    config_lines = File.read('config/unicorn.rb.example').split("\n")
+    project_root = File.expand_path('../..', __dir__)
+
+    config_lines = File.read('config/unicorn.rb.example')
+      .gsub('/home/git/gitlab', project_root)
+      .gsub('/home/git', project_root)
+      .split("\n")
 
     # Remove these because they make setup harder.
     config_lines = config_lines.reject do |line|
       %w[
-        working_directory
         worker_processes
         listen
         pid
@@ -26,33 +32,18 @@ describe 'Unicorn' do
     # predictable which process will handle our requests.
     config_lines << 'worker_processes 1'
 
-    @socket_path = File.join(Dir.pwd, 'tmp/tests/unicorn.socket')
+    @socket_path = File.join(project_root, 'tmp/tests/unicorn.socket')
     config_lines << "listen '#{@socket_path}'"
 
-    ready_file = 'tmp/tests/unicorn-worker-ready'
+    ready_file = File.join(project_root, 'tmp/tests/unicorn-worker-ready')
     FileUtils.rm_f(ready_file)
     after_fork_index = config_lines.index { |l| l.start_with?('after_fork') }
     config_lines.insert(after_fork_index + 1, "File.write('#{ready_file}', Process.pid)")
 
-    config_path = 'tmp/tests/unicorn.rb'
+    config_path = File.join(project_root, 'tmp/tests/unicorn.rb')
     File.write(config_path, config_lines.join("\n") + "\n")
 
-    rackup_path = 'tmp/tests/config.ru'
-    File.write(rackup_path, <<~EOS)
-      app =
-        proc do |env|
-          if env['REQUEST_METHOD'] == 'GET'
-            [200, {}, [Process.pid]]
-          else
-            Process.kill(env['QUERY_STRING'], Process.pid)
-            [200, {}, ['Bye!']]
-          end
-        end
-
-      run app
-    EOS
-
-    cmd = %W[unicorn -E test -c #{config_path} #{rackup_path}]
+    cmd = %W[unicorn -E test -c #{config_path} spec/rack_servers/configs/config.ru]
     @unicorn_master_pid = spawn(*cmd)
     wait_unicorn_boot!(@unicorn_master_pid, ready_file)
     WebMock.allow_net_connect!