fail benchmarks with errors in a child rpc thread

src/ruby/qps/client.rb

@@ -89,12 +89,14 @@ class BenchmarkClient
                    payload: gtp.new(type: gtpt::COMPRESSABLE,
                                     body: nulls(simple_params.req_size)))
 
+    @child_threads = []
+
     (0..config.client_channels-1).each do |chan|
       gtbss = Grpc::Testing::BenchmarkService::Stub
       st = config.server_targets
       stub = gtbss.new(st[chan % st.length], cred, **opts)
       (0..config.outstanding_rpcs_per_channel-1).each do |r|
-        Thread.new {
+        @child_threads << Thread.new {
           case config.load_params.load.to_s
           when 'closed_loop'
             waiter = nil
@@ -162,5 +164,8 @@ class BenchmarkClient
   end
   def shutdown
     @done = true
+    @child_threads.each do |thread|
+      thread.join
+    end
   end
 end

src/ruby/qps/server.rb

@@ -71,7 +71,8 @@ class BenchmarkServer
     else
       cred = :this_port_is_insecure
     end
-    @server = GRPC::RpcServer.new
+    # Make sure server can handle the large number of calls in benchmarks
+    @server = GRPC::RpcServer.new(pool_size: 100, max_waiting_requests: 100)
     @port = @server.add_http2_port("0.0.0.0:" + port.to_s, cred)
     @server.handle(BenchmarkServiceImpl.new)
     @start_time = Time.now

src/ruby/qps/worker.rb

@@ -64,8 +64,8 @@ class WorkerServiceImpl < Grpc::Testing::WorkerService::Service
           q.push(gtss.new(stats: bms.mark(req.mark.reset), cores: cpu_cores))
         end
       end
-      q.push(self)
       bms.stop
+      q.push(self)
     }
     q.each_item
   end
@@ -83,8 +83,8 @@ class WorkerServiceImpl < Grpc::Testing::WorkerService::Service
                                                    client.mark(req.mark.reset)))
         end
       end
-      q.push(self)
       client.shutdown
+      q.push(self)
     }
     q.each_item
   end
@@ -118,6 +118,10 @@ def main
       options['server_port'] = v
     end
   end.parse!
+
+  # Configure any errors with client or server child threads to surface
+  Thread.abort_on_exception = true
+  
   s = GRPC::RpcServer.new
   s.add_http2_port("0.0.0.0:" + options['driver_port'].to_s,
                    :this_port_is_insecure)