From 262440004b82dbf97b386374ae0897c4eec33b74 Mon Sep 17 00:00:00 2001
From: Daniel Beardsley <daniel@ifixit.com>
Date: Fri, 8 Mar 2013 03:39:45 -0700
Subject: [PATCH] Unicorn: shut down old master upon first fork

---
 config/unicorn.rb | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+), 0 deletions(-)

diff --git a/config/unicorn.rb b/config/unicorn.rb
index 31f3f45..58b2d13 100644
--- a/config/unicorn.rb
+++ b/config/unicorn.rb
@@ -3,3 +3,27 @@
 worker_processes 3 # amount of unicorn workers to spin up
 timeout 30         # restarts workers that hang for 30 seconds
 preload_app true
+
+# Taken from github: https://github.com/blog/517-unicorn
+# Though everyone uses pretty miuch the same code
+before_fork do |server, worker|
+  ##
+  # When sent a USR2, Unicorn will suffix its pidfile with .oldbin and
+  # immediately start loading up a new version of itself (loaded with a new
+  # version of our app). When this new Unicorn is completely loaded
+  # it will begin spawning workers. The first worker spawned will check to
+  # see if an .oldbin pidfile exists. If so, this means we've just booted up
+  # a new Unicorn and need to tell the old one that it can now die. To do so
+  # we send it a QUIT.
+  #
+  # Using this method we get 0 downtime deploys.
+ 
+  old_pid = "#{server.config[:pid]}.oldbin"
+  if File.exists?(old_pid) && server.pid != old_pid
+    begin
+      Process.kill("QUIT", File.read(old_pid).to_i)
+    rescue Errno::ENOENT, Errno::ESRCH
+      # someone else did our job for us
+    end
+  end
+end
--
libgit2 0.21.2