Merge branch 'master' of github.com:grpc/grpc into lb_pollset_propagation

25 files changed, 98 insertions, 83 deletions

diff --git a/test/core/channel/channel_stack_test.c b/test/core/channel/channel_stack_test.c
index 34180ed279..37481a9342 100644
--- a/test/core/channel/channel_stack_test.c
+++ b/test/core/channel/channel_stack_test.c
@@ -62,8 +62,8 @@ static void call_init_func(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
 static void channel_destroy_func(grpc_exec_ctx *exec_ctx,
                                  grpc_channel_element *elem) {}
 
-static void call_destroy_func(grpc_exec_ctx *exec_ctx,
-                              grpc_call_element *elem) {
+static void call_destroy_func(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+                              void *ignored) {
   ++*(int *)(elem->channel_data);
 }
 
@@ -87,7 +87,7 @@ static void free_channel(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
 }
 
 static void free_call(grpc_exec_ctx *exec_ctx, void *arg, bool success) {
-  grpc_call_stack_destroy(exec_ctx, arg);
+  grpc_call_stack_destroy(exec_ctx, arg, NULL);
   gpr_free(arg);
 }
 
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/03a72675e1969f836094f1ecfec2a7b34418e306 b/test/core/end2end/fuzzers/server_fuzzer_corpus/03a72675e1969f836094f1ecfec2a7b34418e306
new file mode 100644
index 0000000000..503af15fe8
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/03a72675e1969f836094f1ecfec2a7b34418e306
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/0416afd6875d9ba55f1e5f86a6456a5445d5e576 b/test/core/end2end/fuzzers/server_fuzzer_corpus/0416afd6875d9ba55f1e5f86a6456a5445d5e576
new file mode 100644
index 0000000000..30229f98fd
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/0416afd6875d9ba55f1e5f86a6456a5445d5e576
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/08c42ef29eff83052c5887855f2fa3e07ebe470c b/test/core/end2end/fuzzers/server_fuzzer_corpus/08c42ef29eff83052c5887855f2fa3e07ebe470c
new file mode 100644
index 0000000000..828275ee3c
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/08c42ef29eff83052c5887855f2fa3e07ebe470c
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/1ba889ea1543297824e99e641e6ca8b91f45732e b/test/core/end2end/fuzzers/server_fuzzer_corpus/1ba889ea1543297824e99e641e6ca8b91f45732e
new file mode 100644
index 0000000000..6ed060d1e3
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/1ba889ea1543297824e99e641e6ca8b91f45732e
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/3b09bf453c6f93983c24c4d5481e55d66213f93a b/test/core/end2end/fuzzers/server_fuzzer_corpus/3b09bf453c6f93983c24c4d5481e55d66213f93a
new file mode 100644
index 0000000000..1a7a213cd7
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/3b09bf453c6f93983c24c4d5481e55d66213f93a
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/49cb33cbb60f041e8e99dd718993acd2c3354416 b/test/core/end2end/fuzzers/server_fuzzer_corpus/49cb33cbb60f041e8e99dd718993acd2c3354416
new file mode 100644
index 0000000000..7f975251dd
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/49cb33cbb60f041e8e99dd718993acd2c3354416
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/59743fe120be6ae1aed1c02230ee1bb460f621ee b/test/core/end2end/fuzzers/server_fuzzer_corpus/59743fe120be6ae1aed1c02230ee1bb460f621ee
new file mode 100644
index 0000000000..3038fde547
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/59743fe120be6ae1aed1c02230ee1bb460f621ee
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/a5ccb8f124d8ddb5350b90bc0d6b96db280cb7c9 b/test/core/end2end/fuzzers/server_fuzzer_corpus/a5ccb8f124d8ddb5350b90bc0d6b96db280cb7c9
new file mode 100644
index 0000000000..9d39854fc9
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/a5ccb8f124d8ddb5350b90bc0d6b96db280cb7c9
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/a7fac1265a384fe9e45a9ee3d708b79c4e80505e b/test/core/end2end/fuzzers/server_fuzzer_corpus/a7fac1265a384fe9e45a9ee3d708b79c4e80505e
new file mode 100644
index 0000000000..338f61bdce
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/a7fac1265a384fe9e45a9ee3d708b79c4e80505e
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/aaf049720c707d4e14e47e7eb31d6a2dda60e66a b/test/core/end2end/fuzzers/server_fuzzer_corpus/aaf049720c707d4e14e47e7eb31d6a2dda60e66a
new file mode 100644
index 0000000000..dab9c75822
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/aaf049720c707d4e14e47e7eb31d6a2dda60e66a
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/c4e4c7572e005e18d56eac407033da058737a5ab b/test/core/end2end/fuzzers/server_fuzzer_corpus/c4e4c7572e005e18d56eac407033da058737a5ab
new file mode 100644
index 0000000000..070a581b37
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/c4e4c7572e005e18d56eac407033da058737a5ab
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/crash-dae0f07934a527989f23f06e630710ff6ca8c809 b/test/core/end2end/fuzzers/server_fuzzer_corpus/crash-dae0f07934a527989f23f06e630710ff6ca8c809
new file mode 100644
index 0000000000..b6dfd77e67
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/crash-dae0f07934a527989f23f06e630710ff6ca8c809
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/e96ad9c17795e52edc810a08d4fc61fe8790002a b/test/core/end2end/fuzzers/server_fuzzer_corpus/e96ad9c17795e52edc810a08d4fc61fe8790002a
new file mode 100644
index 0000000000..df9241dd0c
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/e96ad9c17795e52edc810a08d4fc61fe8790002a
diff --git a/test/core/end2end/fuzzers/server_fuzzer_corpus/fa202a5f51cd49f8ea5af60c5f403f797c01c504 b/test/core/end2end/fuzzers/server_fuzzer_corpus/fa202a5f51cd49f8ea5af60c5f403f797c01c504
new file mode 100644
index 0000000000..0ba5935164
--- /dev/null
+++ b/test/core/end2end/fuzzers/server_fuzzer_corpus/fa202a5f51cd49f8ea5af60c5f403f797c01c504
diff --git a/test/core/end2end/tests/filter_causes_close.c b/test/core/end2end/tests/filter_causes_close.c
index df36eb7cdf..1a8f531f38 100644
--- a/test/core/end2end/tests/filter_causes_close.c
+++ b/test/core/end2end/tests/filter_causes_close.c
@@ -232,8 +232,8 @@ static void start_transport_stream_op(grpc_exec_ctx *exec_ctx,
 static void init_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
                            grpc_call_element_args *args) {}
 
-static void destroy_call_elem(grpc_exec_ctx *exec_ctx,
-                              grpc_call_element *elem) {}
+static void destroy_call_elem(grpc_exec_ctx *exec_ctx, grpc_call_element *elem,
+                              void *and_free_memory) {}
 
 static void init_channel_elem(grpc_exec_ctx *exec_ctx,
                               grpc_channel_element *elem,
diff --git a/test/core/util/passthru_endpoint.c b/test/core/util/passthru_endpoint.c
index 168ae59e91..ae955b1f68 100644
--- a/test/core/util/passthru_endpoint.c
+++ b/test/core/util/passthru_endpoint.c
@@ -83,11 +83,15 @@ static void me_write(grpc_exec_ctx *exec_ctx, grpc_endpoint *ep,
   if (m->parent->shutdown) {
     ok = false;
   } else if (m->on_read != NULL) {
-    gpr_slice_buffer_addn(m->on_read_out, slices->slices, slices->count);
+    for (size_t i = 0; i < slices->count; i++) {
+      gpr_slice_buffer_add(m->on_read_out, gpr_slice_ref(slices->slices[i]));
+    }
     grpc_exec_ctx_enqueue(exec_ctx, m->on_read, true, NULL);
     m->on_read = NULL;
   } else {
-    gpr_slice_buffer_addn(&m->read_buffer, slices->slices, slices->count);
+    for (size_t i = 0; i < slices->count; i++) {
+      gpr_slice_buffer_add(&m->read_buffer, gpr_slice_ref(slices->slices[i]));
+    }
   }
   gpr_mu_unlock(&m->parent->mu);
   grpc_exec_ctx_enqueue(exec_ctx, cb, ok, NULL);
diff --git a/test/core/util/test_config.c b/test/core/util/test_config.c
index 62468a5a61..270d16600d 100644
--- a/test/core/util/test_config.c
+++ b/test/core/util/test_config.c
@@ -210,7 +210,7 @@ static void install_crash_handler() {
 #include <stdio.h>
 #include <string.h>
 
-static char g_alt_stack[MINSIGSTKSZ];
+static char g_alt_stack[GPR_MAX(MINSIGSTKSZ, 65536)];
 
 #define MAX_FRAMES 32
 
diff --git a/test/cpp/interop/stress_interop_client.cc b/test/cpp/interop/stress_interop_client.cc
index 04671fb935..f287a5aa3b 100644
--- a/test/cpp/interop/stress_interop_client.cc
+++ b/test/cpp/interop/stress_interop_client.cc
@@ -84,49 +84,37 @@ StressTestInteropClient::StressTestInteropClient(
     int test_id, const grpc::string& server_address,
     std::shared_ptr<Channel> channel,
     const WeightedRandomTestSelector& test_selector, long test_duration_secs,
-    long sleep_duration_ms, long metrics_collection_interval_secs)
+    long sleep_duration_ms)
     : test_id_(test_id),
       server_address_(server_address),
       channel_(channel),
       interop_client_(new InteropClient(channel, false)),
       test_selector_(test_selector),
       test_duration_secs_(test_duration_secs),
-      sleep_duration_ms_(sleep_duration_ms),
-      metrics_collection_interval_secs_(metrics_collection_interval_secs) {}
+      sleep_duration_ms_(sleep_duration_ms) {}
 
-void StressTestInteropClient::MainLoop(std::shared_ptr<Gauge> qps_gauge) {
+void StressTestInteropClient::MainLoop(std::shared_ptr<QpsGauge> qps_gauge) {
   gpr_log(GPR_INFO, "Running test %d. ServerAddr: %s", test_id_,
           server_address_.c_str());
 
-  gpr_timespec test_end_time =
-      gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
-                   gpr_time_from_seconds(test_duration_secs_, GPR_TIMESPAN));
+  gpr_timespec test_end_time;
+  if (test_duration_secs_ < 0) {
+    test_end_time = gpr_inf_future(GPR_CLOCK_REALTIME);
+  } else {
+    test_end_time =
+        gpr_time_add(gpr_now(GPR_CLOCK_REALTIME),
+                     gpr_time_from_seconds(test_duration_secs_, GPR_TIMESPAN));
+  }
 
-  gpr_timespec current_time = gpr_now(GPR_CLOCK_REALTIME);
-  gpr_timespec next_stat_collection_time = current_time;
-  gpr_timespec collection_interval =
-      gpr_time_from_seconds(metrics_collection_interval_secs_, GPR_TIMESPAN);
-  long num_calls_per_interval = 0;
+  qps_gauge->Reset();
 
-  while (test_duration_secs_ < 0 ||
-         gpr_time_cmp(gpr_now(GPR_CLOCK_REALTIME), test_end_time) < 0) {
+  while (gpr_time_cmp(gpr_now(GPR_CLOCK_REALTIME), test_end_time) < 0) {
     // Select the test case to execute based on the weights and execute it
     TestCaseType test_case = test_selector_.GetNextTest();
     gpr_log(GPR_DEBUG, "%d - Executing the test case %d", test_id_, test_case);
     RunTest(test_case);
 
-    num_calls_per_interval++;
-
-    // See if its time to collect stats yet
-    current_time = gpr_now(GPR_CLOCK_REALTIME);
-    if (gpr_time_cmp(next_stat_collection_time, current_time) < 0) {
-      qps_gauge->Set(num_calls_per_interval /
-                     metrics_collection_interval_secs_);
-
-      num_calls_per_interval = 0;
-      next_stat_collection_time =
-          gpr_time_add(current_time, collection_interval);
-    }
+    qps_gauge->Incr();
 
     // Sleep between successive calls if needed
     if (sleep_duration_ms_ > 0) {
diff --git a/test/cpp/interop/stress_interop_client.h b/test/cpp/interop/stress_interop_client.h
index 6fd303d6b7..cb0cd98821 100644
--- a/test/cpp/interop/stress_interop_client.h
+++ b/test/cpp/interop/stress_interop_client.h
@@ -87,12 +87,11 @@ class StressTestInteropClient {
   StressTestInteropClient(int test_id, const grpc::string& server_address,
                           std::shared_ptr<Channel> channel,
                           const WeightedRandomTestSelector& test_selector,
-                          long test_duration_secs, long sleep_duration_ms,
-                          long metrics_collection_interval_secs);
+                          long test_duration_secs, long sleep_duration_ms);
 
   // The main function. Use this as the thread entry point.
-  // qps_gauge is the Gauge to record the requests per second metric
-  void MainLoop(std::shared_ptr<Gauge> qps_gauge);
+  // qps_gauge is the QpsGauge to record the requests per second metric
+  void MainLoop(std::shared_ptr<QpsGauge> qps_gauge);
 
  private:
   void RunTest(TestCaseType test_case);
@@ -104,7 +103,6 @@ class StressTestInteropClient {
   const WeightedRandomTestSelector& test_selector_;
   long test_duration_secs_;
   long sleep_duration_ms_;
-  long metrics_collection_interval_secs_;
 };
 
 }  // namespace testing
diff --git a/test/cpp/interop/stress_test.cc b/test/cpp/interop/stress_test.cc
index 38caf31b76..d9e3fd25c5 100644
--- a/test/cpp/interop/stress_test.cc
+++ b/test/cpp/interop/stress_test.cc
@@ -56,9 +56,6 @@ extern void gpr_default_log(gpr_log_func_args* args);
 
 DEFINE_int32(metrics_port, 8081, "The metrics server port.");
 
-DEFINE_int32(metrics_collection_interval_secs, 5,
-             "How often (in seconds) should metrics be recorded.");
-
 DEFINE_int32(sleep_duration_ms, 0,
              "The duration (in millisec) between two"
              " consecutive test calls (per server) issued by the server.");
@@ -275,19 +272,19 @@ int main(int argc, char** argv) {
            stub_idx++) {
         StressTestInteropClient* client = new StressTestInteropClient(
             ++thread_idx, *it, channel, test_selector, FLAGS_test_duration_secs,
-            FLAGS_sleep_duration_ms, FLAGS_metrics_collection_interval_secs);
+            FLAGS_sleep_duration_ms);
 
-        bool is_already_created;
-        // Gauge name
+        bool is_already_created = false;
+        // QpsGauge name
         std::snprintf(buffer, sizeof(buffer),
                       "/stress_test/server_%d/channel_%d/stub_%d/qps",
                       server_idx, channel_idx, stub_idx);
 
         test_threads.emplace_back(grpc::thread(
             &StressTestInteropClient::MainLoop, client,
-            metrics_service.CreateGauge(buffer, &is_already_created)));
+            metrics_service.CreateQpsGauge(buffer, &is_already_created)));
 
-        // The Gauge should not have been already created
+        // The QpsGauge should not have been already created
         GPR_ASSERT(!is_already_created);
       }
     }
diff --git a/test/cpp/qps/client.h b/test/cpp/qps/client.h
index 5a9027a4a2..175529f01b 100644
--- a/test/cpp/qps/client.h
+++ b/test/cpp/qps/client.h
@@ -39,6 +39,7 @@
 #include <vector>
 
 #include <grpc++/support/byte_buffer.h>
+#include <grpc++/support/channel_arguments.h>
 #include <grpc++/support/slice.h>
 #include <grpc/support/log.h>
 #include <grpc/support/time.h>
@@ -280,7 +281,7 @@ class ClientImpl : public Client {
         create_stub_(create_stub) {
     for (int i = 0; i < config.client_channels(); i++) {
       channels_[i].init(config.server_targets(i % config.server_targets_size()),
-                        config, create_stub_);
+                        config, create_stub_, i);
     }
 
     ClientRequestCreator<RequestType> create_req(&request_,
@@ -303,14 +304,17 @@ class ClientImpl : public Client {
     }
     void init(const grpc::string& target, const ClientConfig& config,
               std::function<std::unique_ptr<StubType>(std::shared_ptr<Channel>)>
-                  create_stub) {
+                  create_stub,
+              int shard) {
       // We have to use a 2-phase init like this with a default
       // constructor followed by an initializer function to make
       // old compilers happy with using this in std::vector
+      ChannelArguments args;
+      args.SetInt("shard_to_ensure_no_subchannel_merges", shard);
       channel_ = CreateTestChannel(
           target, config.security_params().server_host_override(),
-          config.has_security_params(),
-          !config.security_params().use_test_ca());
+          config.has_security_params(), !config.security_params().use_test_ca(),
+          std::shared_ptr<CallCredentials>(), args);
       stub_ = create_stub(channel_);
     }
     Channel* get_channel() { return channel_.get(); }
diff --git a/test/cpp/qps/driver.cc b/test/cpp/qps/driver.cc
index 2583ceb819..04b2b453f9 100644
--- a/test/cpp/qps/driver.cc
+++ b/test/cpp/qps/driver.cc
@@ -83,6 +83,7 @@ static std::unordered_map<string, std::deque<int>> get_hosts_and_cores(
       auto stub = WorkerService::NewStub(
           CreateChannel(*it, InsecureChannelCredentials()));
       grpc::ClientContext ctx;
+      ctx.set_fail_fast(false);
       CoreRequest dummy;
       CoreResponse cores;
       grpc::Status s = stub->CoreCount(&ctx, dummy, &cores);
@@ -166,6 +167,7 @@ namespace runsc {
 static ClientContext* AllocContext(list<ClientContext>* contexts) {
   contexts->emplace_back();
   auto context = &contexts->back();
+  context->set_fail_fast(false);
   return context;
 }
 
@@ -435,6 +437,7 @@ void RunQuit() {
         CreateChannel(workers[i], InsecureChannelCredentials()));
     Void dummy;
     grpc::ClientContext ctx;
+    ctx.set_fail_fast(false);
     GPR_ASSERT(stub->QuitWorker(&ctx, dummy, &dummy).ok());
   }
 }
diff --git a/test/cpp/util/metrics_server.cc b/test/cpp/util/metrics_server.cc
index d9b44a6a92..cc6b39b753 100644
--- a/test/cpp/util/metrics_server.cc
+++ b/test/cpp/util/metrics_server.cc
@@ -42,16 +42,26 @@
 namespace grpc {
 namespace testing {
 
-Gauge::Gauge(long initial_val) : val_(initial_val) {}
+QpsGauge::QpsGauge()
+    : start_time_(gpr_now(GPR_CLOCK_REALTIME)), num_queries_(0) {}
 
-void Gauge::Set(long new_val) {
-  std::lock_guard<std::mutex> lock(val_mu_);
-  val_ = new_val;
+void QpsGauge::Reset() {
+  std::lock_guard<std::mutex> lock(num_queries_mu_);
+  num_queries_ = 0;
+  start_time_ = gpr_now(GPR_CLOCK_REALTIME);
 }
 
-long Gauge::Get() {
-  std::lock_guard<std::mutex> lock(val_mu_);
-  return val_;
+void QpsGauge::Incr() {
+  std::lock_guard<std::mutex> lock(num_queries_mu_);
+  num_queries_++;
+}
+
+long QpsGauge::Get() {
+  std::lock_guard<std::mutex> lock(num_queries_mu_);
+  gpr_timespec time_diff =
+      gpr_time_sub(gpr_now(GPR_CLOCK_REALTIME), start_time_);
+  long duration_secs = time_diff.tv_sec > 0 ? time_diff.tv_sec : 1;
+  return num_queries_ / duration_secs;
 }
 
 grpc::Status MetricsServiceImpl::GetAllGauges(
@@ -60,7 +70,7 @@ grpc::Status MetricsServiceImpl::GetAllGauges(
   gpr_log(GPR_DEBUG, "GetAllGauges called");
 
   std::lock_guard<std::mutex> lock(mu_);
-  for (auto it = gauges_.begin(); it != gauges_.end(); it++) {
+  for (auto it = qps_gauges_.begin(); it != qps_gauges_.end(); it++) {
     GaugeResponse resp;
     resp.set_name(it->first);                // Gauge name
     resp.set_long_value(it->second->Get());  // Gauge value
@@ -75,8 +85,8 @@ grpc::Status MetricsServiceImpl::GetGauge(ServerContext* context,
                                           GaugeResponse* response) {
   std::lock_guard<std::mutex> lock(mu_);
 
-  const auto it = gauges_.find(request->name());
-  if (it != gauges_.end()) {
+  const auto it = qps_gauges_.find(request->name());
+  if (it != qps_gauges_.end()) {
     response->set_name(it->first);
     response->set_long_value(it->second->Get());
   }
@@ -84,16 +94,17 @@ grpc::Status MetricsServiceImpl::GetGauge(ServerContext* context,
   return Status::OK;
 }
 
-std::shared_ptr<Gauge> MetricsServiceImpl::CreateGauge(const grpc::string& name,
-                                                       bool* already_present) {
+std::shared_ptr<QpsGauge> MetricsServiceImpl::CreateQpsGauge(
+    const grpc::string& name, bool* already_present) {
   std::lock_guard<std::mutex> lock(mu_);
 
-  std::shared_ptr<Gauge> gauge(new Gauge(0));
-  const auto p = gauges_.emplace(name, gauge);
+  std::shared_ptr<QpsGauge> qps_gauge(new QpsGauge());
+  const auto p = qps_gauges_.emplace(name, qps_gauge);
 
-  // p.first is an iterator pointing to <name, shared_ptr<Gauge>> pair. p.second
-  // is a boolean which is set to 'true' if the Gauge is inserted in the guages_
-  // map and 'false' if it is already present in the map
+  // p.first is an iterator pointing to <name, shared_ptr<QpsGauge>> pair.
+  // p.second is a boolean which is set to 'true' if the QpsGauge is
+  // successfully inserted in the guages_ map and 'false' if it is already
+  // present in the map
   *already_present = !p.second;
   return p.first->second;
 }
diff --git a/test/cpp/util/metrics_server.h b/test/cpp/util/metrics_server.h
index ce05e0be64..aa9bfed23d 100644
--- a/test/cpp/util/metrics_server.h
+++ b/test/cpp/util/metrics_server.h
@@ -48,10 +48,13 @@
  * Example:
  *    MetricsServiceImpl metricsImpl;
  *    ..
- *    // Create Gauge(s). Note: Gauges can be created even after calling
+ *    // Create QpsGauge(s). Note: QpsGauges can be created even after calling
  *    // 'StartServer'.
- *    Gauge gauge1 = metricsImpl.CreateGauge("foo",is_present);
- *    // gauge1 can now be used anywhere in the program to set values.
+ *    QpsGauge qps_gauge1 = metricsImpl.CreateQpsGauge("foo", is_present);
+ *    // qps_gauge1 can now be used anywhere in the program by first making a
+ *    // one-time call qps_gauge1.Reset() and then calling qps_gauge1.Incr()
+ *    // every time to increment a query counter
+ *
  *    ...
  *    // Create the metrics server
  *    std::unique_ptr<grpc::Server> server = metricsImpl.StartServer(port);
@@ -60,17 +63,24 @@
 namespace grpc {
 namespace testing {
 
-// TODO(sreek): Add support for other types of Gauges like Double, String in
-// future
-class Gauge {
+class QpsGauge {
  public:
-  Gauge(long initial_val);
-  void Set(long new_val);
+  QpsGauge();
+
+  // Initialize the internal timer and reset the query count to 0
+  void Reset();
+
+  // Increment the query count by 1
+  void Incr();
+
+  // Return the current qps (i.e query count divided by the time since this
+  // QpsGauge object created (or Reset() was called))
   long Get();
 
  private:
-  long val_;
-  std::mutex val_mu_;
+  gpr_timespec start_time_;
+  long num_queries_;
+  std::mutex num_queries_mu_;
 };
 
 class MetricsServiceImpl GRPC_FINAL : public MetricsService::Service {
@@ -81,17 +91,17 @@ class MetricsServiceImpl GRPC_FINAL : public MetricsService::Service {
   grpc::Status GetGauge(ServerContext* context, const GaugeRequest* request,
                         GaugeResponse* response) GRPC_OVERRIDE;
 
-  // Create a Gauge with name 'name'. is_present is set to true if the Gauge
+  // Create a QpsGauge with name 'name'. is_present is set to true if the Gauge
   // is already present in the map.
-  // NOTE: CreateGauge can be called anytime (i.e before or after calling
+  // NOTE: CreateQpsGauge can be called anytime (i.e before or after calling
   // StartServer).
-  std::shared_ptr<Gauge> CreateGauge(const grpc::string& name,
-                                     bool* already_present);
+  std::shared_ptr<QpsGauge> CreateQpsGauge(const grpc::string& name,
+                                           bool* already_present);
 
   std::unique_ptr<grpc::Server> StartServer(int port);
 
  private:
-  std::map<string, std::shared_ptr<Gauge>> gauges_;
+  std::map<string, std::shared_ptr<QpsGauge>> qps_gauges_;
   std::mutex mu_;
 };