diff --git a/CHANGELOG b/CHANGELOG
index 1bf2ce7..ab803e3 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -5,6 +5,7 @@
 - Support changing the name of the "git" user / group (Michael Fenn)
 - Configure omniauth in gitlab.yml
 - Expose more fields under 'extra' in gitlab.yml
+- Zero-downtime Unicorn restarts
 
 6.9.0
 - Make SSH port in clone URLs configurable (Julien Pivotto)
diff --git a/README.md b/README.md
index 992f8eb..5d988f8 100644
--- a/README.md
+++ b/README.md
@@ -131,7 +131,13 @@ sudo gitlab-ctl restart
 It is also possible to start, stop or restart individual components.
 
 ```shell
-sudo gitlab-ctl restart unicorn
+sudo gitlab-ctl restart sidekiq
+```
+
+Unicorn supports zero-downtime reloads. These can be triggered as follows:
+
+```shell
+sudo gitlab-ctl hup unicorn
 ```
 
 ## Configuration
diff --git a/files/gitlab-cookbooks/gitlab/attributes/default.rb b/files/gitlab-cookbooks/gitlab/attributes/default.rb
index 22f1bdb..2580d72 100644
--- a/files/gitlab-cookbooks/gitlab/attributes/default.rb
+++ b/files/gitlab-cookbooks/gitlab/attributes/default.rb
@@ -146,6 +146,7 @@ default['gitlab']['unicorn']['worker_processes'] = 2
 default['gitlab']['unicorn']['listen'] = '127.0.0.1'
 default['gitlab']['unicorn']['port'] = 8080
 default['gitlab']['unicorn']['socket'] = '/var/opt/gitlab/gitlab-rails/tmp/sockets/gitlab.socket'
+default['gitlab']['unicorn']['pidfile'] = '/opt/gitlab/var/unicorn/unicorn.pid'
 default['gitlab']['unicorn']['tcp_nopush'] = true
 default['gitlab']['unicorn']['backlog_socket'] = 64
 default['gitlab']['unicorn']['worker_timeout'] = 30
diff --git a/files/gitlab-cookbooks/gitlab/recipes/unicorn.rb b/files/gitlab-cookbooks/gitlab/recipes/unicorn.rb
index 5f5b49f..0984b4f 100644
--- a/files/gitlab-cookbooks/gitlab/recipes/unicorn.rb
+++ b/files/gitlab-cookbooks/gitlab/recipes/unicorn.rb
@@ -21,12 +21,14 @@ gitlab_rails_etc_dir = File.join(gitlab_rails_dir, "etc")
 gitlab_rails_working_dir = File.join(gitlab_rails_dir, "working")
 
 unicorn_listen_socket = node['gitlab']['unicorn']['socket']
+unicorn_pidfile = node['gitlab']['unicorn']['pidfile']
 unicorn_log_dir = node['gitlab']['unicorn']['log_directory']
 unicorn_socket_dir = File.dirname(unicorn_listen_socket)
 
 [
   unicorn_log_dir,
-  unicorn_socket_dir
+  unicorn_socket_dir,
+  File.dirname(unicorn_pidfile)
 ].each do |dir_name|
   directory dir_name do
     owner node['gitlab']['user']['username']
@@ -51,6 +53,19 @@ unicorn_config File.join(gitlab_rails_etc_dir, "unicorn.rb") do
   working_directory gitlab_rails_working_dir
   worker_processes node['gitlab']['unicorn']['worker_processes']
   preload_app true
+  stderr_path File.join(unicorn_log_dir, "unicorn_stderr.log")
+  stdout_path File.join(unicorn_log_dir, "unicorn_stdout.log")
+  pid unicorn_pidfile
+  before_fork <<-'EOS'
+    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
+  EOS
   owner "root"
   group "root"
   mode "0644"
@@ -59,6 +74,7 @@ end
 
 runit_service "unicorn" do
   down node['gitlab']['unicorn']['ha']
+  restart_command 2 # Restart Unicorn using SIGUSR2
   options({
     :log_directory => unicorn_log_dir
   }.merge(params))
diff --git a/files/gitlab-cookbooks/gitlab/templates/default/sv-unicorn-run.erb b/files/gitlab-cookbooks/gitlab/templates/default/sv-unicorn-run.erb
index 90bf977..32967d6 100644
--- a/files/gitlab-cookbooks/gitlab/templates/default/sv-unicorn-run.erb
+++ b/files/gitlab-cookbooks/gitlab/templates/default/sv-unicorn-run.erb
@@ -1,6 +1,99 @@
-#!/bin/sh
-
-cd /opt/gitlab/embedded/service/gitlab-rails
+#!/bin/bash
 
+# Let runit capture all script error messages
 exec 2>&1
-exec chpst -P -U <%= node['gitlab']['user']['username'] %> -u <%= node['gitlab']['user']['username'] %> /usr/bin/env HOME="<%= node['gitlab']['user']['home'] %>" /opt/gitlab/embedded/bin/bundle exec unicorn -E <%= node['gitlab']['gitlab-rails']['environment'] %> -c <%= File.join(node['gitlab']['gitlab-rails']['dir'], "etc", "unicorn.rb") %> /opt/gitlab/embedded/service/gitlab-rails/config.ru
+
+readonly current_pidfile=<%= node['gitlab']['unicorn']['pidfile'] %>
+readonly oldbin_pidfile=${current_pidfile}.oldbin
+readonly unicorn_wait_start=1 # time in seconds
+readonly unicorn_poll_alive=1 # time in seconds
+
+function main
+{
+  cd /opt/gitlab/embedded/service/gitlab-rails
+  find_us_a_unicorn
+  trap_signals
+  wait_for_unicorn_to_exit
+}
+
+function find_us_a_unicorn
+{
+  adopt ${current_pidfile}
+  if [[ ${unicorn_pid} ]]; then
+    echo "adopted existing unicorn master ${unicorn_pid}"
+    return
+  fi
+
+  adopt ${oldbin_pidfile}
+  if [[ ${unicorn_pid} ]]; then
+    echo "adopted existing oldbin unicorn master ${unicorn_pid}"
+    return
+  fi
+
+  echo "starting new unicorn master"
+  start_unicorn_master
+  sleep ${unicorn_wait_start}
+
+  adopt ${current_pidfile}
+  if [[ ${unicorn_pid} ]]; then
+    echo "adopted new unicorn master ${unicorn_pid}"
+    return
+  fi
+
+  echo "failed to start a new unicorn master"
+  exit
+}
+
+function adopt
+{
+  local pid=$(cat $1 2>/dev/null)
+  if alive ${pid} && is_unicorn ${pid}; then
+    readonly unicorn_pid=${pid}
+  fi
+}
+
+function alive
+{
+  kill -0 $1 > /dev/null 2>&1
+}
+
+function is_unicorn
+{
+  ps -p $1 -o args | grep -q unicorn
+}
+
+function start_unicorn_master
+{
+  chpst -P -U <%= node['gitlab']['user']['username'] %> -u <%= node['gitlab']['user']['username'] %> /usr/bin/env HOME="<%= node['gitlab']['user']['home'] %>" /opt/gitlab/embedded/bin/bundle exec unicorn -D -E <%= node['gitlab']['gitlab-rails']['environment'] %> -c <%= File.join(node['gitlab']['gitlab-rails']['dir'], "etc", "unicorn.rb") %> /opt/gitlab/embedded/service/gitlab-rails/config.ru
+}
+
+function trap_signals
+{
+  # Forward all common runit signals except:
+  # - HUP which we handle below;
+  # - KILL which cannot be caught.
+  for sig in STOP CONT ALRM INT QUIT USR1 USR2 TERM; do
+    trap "forward_signal ${sig}" ${sig}
+  done
+
+  # Omnibus-ctl does not have a subcommand that sends USR2 but it can send HUP.
+  # To allow for reloading unicorn from the command line, translate HUP to
+  # USR2.
+  trap "echo 'wrapper received HUP'; forward_signal USR2" HUP
+}
+
+function forward_signal
+{
+  echo "forwarding $1 to unicorn master ${unicorn_pid}"
+  kill -$1 ${unicorn_pid}
+}
+
+function wait_for_unicorn_to_exit
+{
+  while sleep ${unicorn_poll_alive}; do
+    alive ${unicorn_pid} || break
+  done
+}
+
+main
+echo "wrapper for unicorn master ${unicorn_pid} exiting"
--
libgit2 0.21.2