Adds a #run_till_terminated func to RpcServer

- adds signal handling to RpcServer
- ensures that very little behaviour occurs in the signal handling context
- adds #run_till_terminated that launches a server in a thread and then handles
  signals that can be used to stop it.

src/ruby/.rubocop_todo.yml

 # This configuration was generated by `rubocop --auto-gen-config`
-# on 2015-04-15 18:43:23 -0700 using RuboCop version 0.30.0.
+# on 2015-04-16 12:30:09 -0700 using RuboCop version 0.30.0.
 # The point is for the user to remove these configuration records
 # one by one as the offenses are removed from the code base.
 # Note that changes in the inspected code, or installation of new
 # versions of RuboCop, may require this file to be generated again.
 
-# Offense count: 32
+# Offense count: 34
 Metrics/AbcSize:
   Max: 36
 
 # Offense count: 3
 # Configuration parameters: CountComments.
 Metrics/ClassLength:
-  Max: 183
+  Max: 185
 
 # Offense count: 35
 # Configuration parameters: CountComments.
@@ -24,7 +24,7 @@ Metrics/MethodLength:
 Metrics/ParameterLists:
   Max: 8
 
-# Offense count: 6
+# Offense count: 9
 # Configuration parameters: AllowedVariables.
 Style/GlobalVars:
   Enabled: false

src/ruby/lib/grpc/generic/rpc_server.rb

@@ -33,6 +33,9 @@ require 'grpc/generic/service'
 require 'thread'
 require 'xray/thread_dump_signal_handler'
 
+# A global that contains signals the gRPC servers should respond to.
+$grpc_signals = []
+
 # GRPC contains the General RPC module.
 module GRPC
   # RpcServer hosts a number of services and makes them available on the
@@ -50,6 +53,23 @@ module GRPC
     # Default max_waiting_requests size is 20
     DEFAULT_MAX_WAITING_REQUESTS = 20
 
+    # Default poll period is 1s
+    DEFAULT_POLL_PERIOD = 1
+
+    # Signal check period is 0.25s
+    SIGNAL_CHECK_PERIOD = 0.25
+
+    # Sets up a signal handler that adds signals to the signal handling global.
+    #
+    # Signal handlers should do as little as humanly possible.
+    # Here, they just add themselves to $grpc_signals
+    #
+    # RpcServer (and later other parts of gRPC) monitors the signals
+    # $grpc_signals in its own non-signal context.
+    def self.trap_signals
+      %w(INT TERM).each { |sig| trap(sig) { $grpc_signals << sig } }
+    end
+
     # Creates a new RpcServer.
     #
     # The RPC server is configured using keyword arguments.
@@ -79,7 +99,7 @@ module GRPC
     # with not available to new requests
     def initialize(pool_size:DEFAULT_POOL_SIZE,
                    max_waiting_requests:DEFAULT_MAX_WAITING_REQUESTS,
-                   poll_period:INFINITE_FUTURE,
+                   poll_period:DEFAULT_POLL_PERIOD,
                    completion_queue_override:nil,
                    server_override:nil,
                    **kw)
@@ -117,6 +137,13 @@ module GRPC
       return unless @running
       @stopped = true
       @pool.stop
+
+      # TODO: uncomment this:
+      #
+      # This segfaults in the c layer, so its commented out for now.  Shutdown
+      # still occurs, but the c layer has to do the cleanup.
+      #
+      # @server.close
     end
 
     # determines if the server is currently running
@@ -139,7 +166,37 @@ module GRPC
       running?
     end
 
-    # determines if the server is currently stopped
+    # Runs the server in its own thread, then waits for signal INT or TERM on
+    # the current thread to terminate it.
+    def run_till_terminated
+      self.class.trap_signals
+      t = Thread.new { run }
+      wait_till_running
+      loop do
+        sleep SIGNAL_CHECK_PERIOD
+        break unless handle_signals
+      end
+      stop
+      t.join
+    end
+
+    # Handles the signals in $grpc_signals.
+    #
+    # @return false if the server should exit, true if not.
+    def handle_signals
+      loop do
+        sig = $grpc_signals.shift
+        case sig
+        when 'INT'
+          return false
+        when 'TERM'
+          return false
+        end
+      end
+      true
+    end
+
+    # Determines if the server is currently stopped
     def stopped?
       @stopped ||= false
     end
@@ -265,7 +322,10 @@ module GRPC
 
     # Pool is a simple thread pool for running server requests.
     class Pool
-      def initialize(size)
+      # Default keep alive period is 1s
+      DEFAULT_KEEP_ALIVE = 1
+
+      def initialize(size, keep_alive: DEFAULT_KEEP_ALIVE)
         fail 'pool size must be positive' unless size > 0
         @jobs = Queue.new
         @size = size
@@ -273,6 +333,7 @@ module GRPC
         @stop_mutex = Mutex.new
         @stop_cond = ConditionVariable.new
         @workers = []
+        @keep_alive = keep_alive
       end
 
       # Returns the number of jobs waiting
@@ -325,7 +386,6 @@ module GRPC
         @workers.size.times { schedule { throw :exit } }
         @stopped = true
 
-        # TODO: allow configuration of the keepalive period
         keep_alive = 5
         @stop_mutex.synchronize do
           @stop_cond.wait(@stop_mutex, keep_alive) if @workers.size > 0
@@ -333,7 +393,7 @@ module GRPC
 
         # Forcibly shutdown any threads that are still alive.
         if @workers.size > 0
-          logger.warn("forcibly terminating #{@workers.size} worker(s)")
+          logger.info("forcibly terminating #{@workers.size} worker(s)")
           @workers.each do |t|
             next unless t.alive?
             begin
@@ -344,7 +404,6 @@ module GRPC
             end
           end
         end
-
         logger.info('stopped, all workers are shutdown')
       end
     end