From 9e1c2d2358117d0b9afad5da19df77e23ae17dc1 Mon Sep 17 00:00:00 2001
From: Craig Tiller <ctiller@google.com>
Date: Wed, 14 Sep 2016 08:37:10 -0700
Subject: [PATCH] Dont start requests until all clients have gotten connected

---
 test/cpp/qps/client.h | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/test/cpp/qps/client.h b/test/cpp/qps/client.h
index 86543e99fb5..c8809cbc5b6 100644
--- a/test/cpp/qps/client.h
+++ b/test/cpp/qps/client.h
@@ -129,13 +129,17 @@ class HistogramEntry GRPC_FINAL {
 
 class Client {
  public:
-  Client() : timer_(new UsageTimer), interarrival_timer_() {}
+  Client() : timer_(new UsageTimer), interarrival_timer_() {
+    gpr_event_init(&start_requests_);
+  }
   virtual ~Client() {}
 
   ClientStats Mark(bool reset) {
     Histogram latencies;
     UsageTimer::Result timer_result;
 
+    MaybeStartRequests();
+
     // avoid std::vector for old compilers that expect a copy constructor
     if (reset) {
       Histogram* to_merge = new Histogram[threads_.size()];
@@ -189,7 +193,10 @@ class Client {
     }
   }
 
-  void EndThreads() { threads_.clear(); }
+  void EndThreads() {
+    MaybeStartRequests();
+    threads_.clear();
+  }
 
   virtual void DestroyMultithreading() = 0;
   virtual bool ThreadFunc(HistogramEntry* histogram, size_t thread_idx) = 0;
@@ -265,6 +272,13 @@ class Client {
     Thread& operator=(const Thread&);
 
     void ThreadFunc() {
+      while (!gpr_event_wait(
+          &client_->start_requests_,
+          gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
+                       gpr_time_from_seconds(1, GPR_TIMESPAN)))) {
+        gpr_log(GPR_INFO, "Waiting for benchmark to start");
+      }
+
       for (;;) {
         // run the loop body
         HistogramEntry entry;
@@ -302,6 +316,16 @@ class Client {
   size_t threads_remaining_;
   std::condition_variable threads_complete_;
 
+  gpr_event start_requests_;
+  bool started_requests_;
+
+  void MaybeStartRequests() {
+    if (!started_requests_) {
+      started_requests_ = true;
+      gpr_event_set(&start_requests_, (void*)1);
+    }
+  }
+
   void CompleteThread() {
     std::lock_guard<std::mutex> g(thread_completion_mu_);
     threads_remaining_--;