increase max thread pool size in benchmarks and fix shutdown ordering

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

@@ -54,6 +54,7 @@ module GRPC
     DEFAULT_MAX_WAITING_REQUESTS = 60
 
     # Default poll period is 1s
+    # Used for grpc server shutdown and thread pool shutdown timeouts
     DEFAULT_POLL_PERIOD = 1
 
     # Signal check period is 0.25s
@@ -124,10 +125,10 @@ module GRPC
         return if @running_state != :running
         transition_running_state(:stopping)
       end
+      @pool.shutdown
+      @pool.wait_for_termination(@poll_period)
       deadline = from_relative_time(@poll_period)
       @server.close(deadline)
-      @pool.shutdown
-      @pool.wait_for_termination
     end
 
     def running_state

src/ruby/qps/server.rb

@@ -63,7 +63,9 @@ class BenchmarkServer
       cred = :this_port_is_insecure
     end
     # Make sure server can handle the large number of calls in benchmarks
-    @server = GRPC::RpcServer.new(pool_size: 100, max_waiting_requests: 100)
+    # TODO: @apolcyn, if scenario config increases total outstanding
+    # calls then will need to increase the pool size too
+    @server = GRPC::RpcServer.new(pool_size: 1024, max_waiting_requests: 1024)
     @port = @server.add_http2_port("0.0.0.0:" + port.to_s, cred)
     @server.handle(BenchmarkServiceImpl.new)
     @start_time = Time.now