added changes for graceful shutdown for agent in linux

cr https://code.amazon.com/reviews/CR-1313840

Author: Katyal

lib/instance_agent/plugins/codedeploy/command_poller.rb

@@ -89,13 +89,13 @@ def perform
         end
 
         def graceful_shutdown
-          log(:info, "Gracefully shutting down command execution threads now, will wait up to #{WAIT_FOR_ALL_THREADS_TIMEOUT_SECONDS} seconds")
+          log(:info, "Gracefully shutting down agent child threads now, will wait up to #{WAIT_FOR_ALL_THREADS_TIMEOUT_SECONDS} seconds")
           # tell the pool to shutdown in an orderly fashion, allowing in progress work to complete
           @thread_pool.shutdown
           # now wait for all work to complete, wait till the timeout value
           # TODO: Make the timeout configurable in the agent configuration
           @thread_pool.wait_for_termination WAIT_FOR_ALL_THREADS_TIMEOUT_SECONDS
-          log(:info, 'All command execution threads have been shut down')
+          log(:info, 'All agent child threads have been shut down')
         end
 
         def next_command

lib/instance_agent/runner/child.rb

@@ -1,5 +1,6 @@
 # encoding: UTF-8
 require 'process_manager/child'
+require 'thread'
 
 module InstanceAgent
   module Runner
@@ -38,6 +39,28 @@ def run
           runner.run
         end
       end
+      
+      # Stops the master after recieving the kill signal
+      # is overriden from ProcessManager::Daemon::Child 
+      def stop
+        @runner.graceful_shutdown
+        ProcessManager::Log.info('agent exiting now')
+        super
+      end
+
+      # Catches the trap signals and does a default or custom action 
+      # is overriden from ProcessManager::Daemon::Child
+      def trap_signals
+        [:INT, :QUIT, :TERM].each do |sig|
+          trap(sig) do
+            ProcessManager::Log.info "#{description}: Received #{sig} - setting internal shutting down flag and possibly finishing last run"
+            stop_thread = Thread.new {stop}
+            stop_thread.join
+          end
+        end
+        # make sure we do not handle children like the master process
+        trap(:CHLD, 'DEFAULT')
+      end
 
       def description
         if runner

lib/instance_agent/runner/master.rb

@@ -28,6 +28,8 @@ def self.pid_file
         File.join(ProcessManager::Config.config[:pid_dir], "#{ProcessManager::Config.config[:program_name]}.pid")
       end
 
+      # Stops the master after recieving the kill signal
+      # is overriden from ProcessManager::Daemon::Master
       def stop
         if (pid = self.class.find_pid)
           puts "Stopping #{description(pid)}"

lib/winagent.rb

@@ -58,7 +58,7 @@ def service_stop
     log(:info, 'stopping the agent')
     @polling_mutex.synchronize do
       @runner.graceful_shutdown
-      log(:info, 'command execution threads shutdown, agent exiting now')
+      log(:info, 'agent exiting now')
     end
   end