correct regression where monitoring thread crashed out

add logging

lib/demon/base.rb

@@ -50,9 +50,10 @@ class Demon::Base
     "#{Rails.root}/tmp/pids/#{self.class.prefix}_#{@index}.pid"
   end
 
-  def alive?
-    if @pid
-      Demon::Base.alive?(@pid)
+  def alive?(pid=nil)
+    pid ||= @pid
+    if pid
+      Demon::Base.alive?(pid)
     else
       false
     end
@@ -145,13 +146,11 @@ class Demon::Base
   end
 
   def self.alive?(pid)
-    begin
     Process.kill(0, pid)
     true
   rescue
     false
   end
-  end
 
   private
 
@@ -169,11 +168,15 @@ class Demon::Base
   def monitor_parent
     Thread.new do
       while true
+        begin
           unless alive?(@parent_pid)
             Process.kill "TERM", Process.pid
             sleep 10
             Process.kill "KILL", Process.pid
           end
+        rescue => e
+          STDERR.puts "URGENT monitoring thread had an exception #{e}"
+        end
         sleep 1
       end
     end