Using a global lock: only one instance at a time

bin/cerberus

@@ -1,7 +1,13 @@
 #!/usr/bin/env ruby
 
-$: << File.expand_path(File.dirname(__FILE__)) + '/../lib'
+# Add lib dir to load path so that we don't have to be installed in rubygems
+require 'pathname' # Use Pathname to follow symlinks
+CERBERUS_LIB_DIR = File.join(File.dirname(Pathname.new(__FILE__).realpath),'..','lib')
+$: << CERBERUS_LIB_DIR 
 
 require 'cerberus/cli'
+require 'cerberus/latch'
 
-Cerberus::CLI.new(*ARGV)
+Cerberus::Latch.lock('/tmp/cerberus.lock', :lock_ttl => 2 * Cerberus::LOCK_WAIT ) do
+  Cerberus::CLI.new(*ARGV)
+end