From 861cd5d9b08aabb05164e42f464ea3fa34dfefcd Mon Sep 17 00:00:00 2001
From: Sam <sam.saffron@gmail.com>
Date: Mon, 15 Jun 2015 12:36:47 +1000
Subject: [PATCH] FIX: ensure child demon is correctly terminated from parent
 on stop

---
 lib/demon/base.rb                  | 59 +++++++++++++++++++++++++-----
 spec/components/demon/base_spec.rb | 40 ++++++++++++++++++++
 2 files changed, 90 insertions(+), 9 deletions(-)
 create mode 100644 spec/components/demon/base_spec.rb

diff --git a/lib/demon/base.rb b/lib/demon/base.rb
index e7cffd419b..0a7f201726 100644
--- a/lib/demon/base.rb
+++ b/lib/demon/base.rb
@@ -3,6 +3,10 @@ module Demon; end
 # intelligent fork based demonizer
 class Demon::Base
 
+  def self.demons
+    @demons
+  end
+
   def self.start(count=1)
     @demons ||= {}
     count.times do |i|
@@ -31,21 +35,57 @@ class Demon::Base
     end
   end
 
+  attr_reader :pid, :parent_pid, :started, :index
+  attr_accessor :stop_timeout
+
   def initialize(index)
     @index = index
     @pid = nil
     @parent_pid = Process.pid
     @started = false
+    @stop_timeout = 10
   end
 
   def pid_file
     "#{Rails.root}/tmp/pids/#{self.class.prefix}_#{@index}.pid"
   end
 
+  def alive?
+    if @pid
+      Demon::Base.alive?(@pid)
+    else
+      false
+    end
+  end
+
   def stop
     @started = false
     if @pid
+      # TODO configurable stop signal
       Process.kill("HUP",@pid)
+
+      wait_for_stop = lambda {
+        timeout = @stop_timeout
+
+        while alive? && timeout > 0
+          timeout -= (@stop_timeout/10.0)
+          sleep(@stop_timeout/10.0)
+          Process.waitpid(@pid, Process::WNOHANG) rescue -1
+        end
+
+        Process.waitpid(@pid, Process::WNOHANG) rescue -1
+      }
+
+      wait_for_stop.call
+
+      if alive?
+        STDERR.puts "Process would not terminate cleanly, force quitting. pid: #{@pid}"
+        Process.kill("KILL", @pid)
+      end
+
+      wait_for_stop.call
+
+
       @pid = nil
       @started = false
     end
@@ -96,7 +136,7 @@ class Demon::Base
   def already_running?
     if File.exists? pid_file
       pid = File.read(pid_file).to_i
-      if alive?(pid)
+      if Demon::Base.alive?(pid)
         return pid
       end
     end
@@ -104,6 +144,15 @@ class Demon::Base
     nil
   end
 
+  def self.alive?(pid)
+    begin
+      Process.kill(0, pid)
+      true
+    rescue
+      false
+    end
+  end
+
   private
 
   def write_pid_file
@@ -130,14 +179,6 @@ class Demon::Base
     end
   end
 
-  def alive?(pid)
-    begin
-      Process.kill(0, pid)
-      true
-    rescue
-      false
-    end
-  end
 
   def suppress_stdout
     true
diff --git a/spec/components/demon/base_spec.rb b/spec/components/demon/base_spec.rb
new file mode 100644
index 0000000000..58a5811d8b
--- /dev/null
+++ b/spec/components/demon/base_spec.rb
@@ -0,0 +1,40 @@
+require 'spec_helper'
+require 'demon/base'
+
+describe Demon do
+
+  class RudeDemon < Demon::Base
+    def self.prefix
+      "rude"
+    end
+
+    def after_fork
+      Signal.trap("HUP"){}
+      Signal.trap("TERM"){}
+      sleep 999999
+    end
+  end
+
+  it "can terminate rude demons" do
+
+    skip("forking rspec has side effects")
+    # Forking rspec has all sorts of weird side effects
+    #  this spec works but we must skip it to keep rspec
+    #  state happy
+
+
+    RudeDemon.start
+    _,demon = RudeDemon.demons.first
+    pid = demon.pid
+    wait_for {
+      demon.alive?
+    }
+
+    demon.stop_timeout = 0.05
+    demon.stop
+    demon.start
+
+    running = !!(Process.kill(0, pid)) rescue false
+    expect(running).to eq(false)
+  end
+end