Merge remote-tracking branch 'upstream/master' into feature/qps-bazel-test

20 files changed, 106 insertions, 249 deletions

diff --git a/test/core/bad_client/bad_client.cc b/test/core/bad_client/bad_client.cc
index ade23133c5..c03ebcf409 100644
--- a/test/core/bad_client/bad_client.cc
+++ b/test/core/bad_client/bad_client.cc
@@ -115,7 +115,7 @@ void grpc_run_client_side_validator(grpc_bad_client_arg* arg, uint32_t flags,
                     grpc_schedule_on_exec_ctx);
 
   /* Write data */
-  grpc_endpoint_write(sfd->client, &outgoing, &done_write_closure, nullptr);
+  grpc_endpoint_write(sfd->client, &outgoing, &done_write_closure);
   grpc_core::ExecCtx::Get()->Flush();
 
   /* Await completion, unless the request is large and write may not finish
diff --git a/test/core/end2end/bad_server_response_test.cc b/test/core/end2end/bad_server_response_test.cc
index f7396a1684..3d133cfc18 100644
--- a/test/core/end2end/bad_server_response_test.cc
+++ b/test/core/end2end/bad_server_response_test.cc
@@ -104,7 +104,7 @@ static void handle_write() {
 
   grpc_slice_buffer_reset_and_unref(&state.outgoing_buffer);
   grpc_slice_buffer_add(&state.outgoing_buffer, slice);
-  grpc_endpoint_write(state.tcp, &state.outgoing_buffer, &on_write, nullptr);
+  grpc_endpoint_write(state.tcp, &state.outgoing_buffer, &on_write);
 }
 
 static void handle_read(void* arg, grpc_error* error) {
diff --git a/test/core/end2end/fixtures/http_proxy_fixture.cc b/test/core/end2end/fixtures/http_proxy_fixture.cc
index ea9c000efb..f02fa9d998 100644
--- a/test/core/end2end/fixtures/http_proxy_fixture.cc
+++ b/test/core/end2end/fixtures/http_proxy_fixture.cc
@@ -201,7 +201,7 @@ static void on_client_write_done(void* arg, grpc_error* error) {
                                 &conn->client_write_buffer);
     conn->client_is_writing = true;
     grpc_endpoint_write(conn->client_endpoint, &conn->client_write_buffer,
-                        &conn->on_client_write_done, nullptr);
+                        &conn->on_client_write_done);
   } else {
     // No more writes.  Unref the connection.
     proxy_connection_unref(conn, "write_done");
@@ -226,7 +226,7 @@ static void on_server_write_done(void* arg, grpc_error* error) {
                                 &conn->server_write_buffer);
     conn->server_is_writing = true;
     grpc_endpoint_write(conn->server_endpoint, &conn->server_write_buffer,
-                        &conn->on_server_write_done, nullptr);
+                        &conn->on_server_write_done);
   } else {
     // No more writes.  Unref the connection.
     proxy_connection_unref(conn, "server_write");
@@ -257,7 +257,7 @@ static void on_client_read_done(void* arg, grpc_error* error) {
     proxy_connection_ref(conn, "client_read");
     conn->server_is_writing = true;
     grpc_endpoint_write(conn->server_endpoint, &conn->server_write_buffer,
-                        &conn->on_server_write_done, nullptr);
+                        &conn->on_server_write_done);
   }
   // Read more data.
   grpc_endpoint_read(conn->client_endpoint, &conn->client_read_buffer,
@@ -288,7 +288,7 @@ static void on_server_read_done(void* arg, grpc_error* error) {
     proxy_connection_ref(conn, "server_read");
     conn->client_is_writing = true;
     grpc_endpoint_write(conn->client_endpoint, &conn->client_write_buffer,
-                        &conn->on_client_write_done, nullptr);
+                        &conn->on_client_write_done);
   }
   // Read more data.
   grpc_endpoint_read(conn->server_endpoint, &conn->server_read_buffer,
@@ -340,7 +340,7 @@ static void on_server_connect_done(void* arg, grpc_error* error) {
   grpc_slice_buffer_add(&conn->client_write_buffer, slice);
   conn->client_is_writing = true;
   grpc_endpoint_write(conn->client_endpoint, &conn->client_write_buffer,
-                      &conn->on_write_response_done, nullptr);
+                      &conn->on_write_response_done);
 }
 
 /**
diff --git a/test/core/iomgr/BUILD b/test/core/iomgr/BUILD
index 675d9e6278..002671a5fa 100644
--- a/test/core/iomgr/BUILD
+++ b/test/core/iomgr/BUILD
@@ -247,19 +247,6 @@ grpc_cc_test(
 )
 
 grpc_cc_test(
-    name = "buffer_list_test",
-    srcs = ["buffer_list_test.cc"],
-    language = "C++",
-    deps = [
-        "//:gpr",
-        "//:grpc",
-        "//test/core/util:gpr_test_util",
-        "//test/core/util:grpc_test_util",
-    ],
-)
-
-
-grpc_cc_test(
     name = "tcp_server_posix_test",
     srcs = ["tcp_server_posix_test.cc"],
     language = "C++",
diff --git a/test/core/iomgr/buffer_list_test.cc b/test/core/iomgr/buffer_list_test.cc
deleted file mode 100644
index f1773580bd..0000000000
--- a/test/core/iomgr/buffer_list_test.cc
+++ /dev/null
@@ -1,111 +0,0 @@
-/*
- *
- * Copyright 2018 gRPC authors.
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *     http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- *
- */
-
-#include "src/core/lib/iomgr/port.h"
-
-#include "src/core/lib/iomgr/buffer_list.h"
-
-#include <grpc/grpc.h>
-
-#include "test/core/util/test_config.h"
-
-#ifdef GRPC_LINUX_ERRQUEUE
-
-static void TestShutdownFlushesListVerifier(void* arg,
-                                            grpc_core::Timestamps* ts,
-                                            grpc_error* error) {
-  GPR_ASSERT(error == GRPC_ERROR_NONE);
-  GPR_ASSERT(arg != nullptr);
-  gpr_atm* done = reinterpret_cast<gpr_atm*>(arg);
-  gpr_atm_rel_store(done, static_cast<gpr_atm>(1));
-}
-
-/** Tests that all TracedBuffer elements in the list are flushed out on
- * shutdown.
- * Also tests that arg is passed correctly.
- */
-static void TestShutdownFlushesList() {
-  grpc_core::grpc_tcp_set_write_timestamps_callback(
-      TestShutdownFlushesListVerifier);
-  grpc_core::TracedBuffer* list = nullptr;
-#define NUM_ELEM 5
-  gpr_atm verifier_called[NUM_ELEM];
-  for (auto i = 0; i < NUM_ELEM; i++) {
-    gpr_atm_rel_store(&verifier_called[i], static_cast<gpr_atm>(0));
-    grpc_core::TracedBuffer::AddNewEntry(
-        &list, i, static_cast<void*>(&verifier_called[i]));
-  }
-  grpc_core::TracedBuffer::Shutdown(&list, GRPC_ERROR_NONE);
-  GPR_ASSERT(list == nullptr);
-  for (auto i = 0; i < NUM_ELEM; i++) {
-    GPR_ASSERT(gpr_atm_acq_load(&verifier_called[i]) ==
-               static_cast<gpr_atm>(1));
-  }
-}
-
-static void TestVerifierCalledOnAckVerifier(void* arg,
-                                            grpc_core::Timestamps* ts,
-                                            grpc_error* error) {
-  GPR_ASSERT(error == GRPC_ERROR_NONE);
-  GPR_ASSERT(arg != nullptr);
-  GPR_ASSERT(ts->acked_time.clock_type == GPR_CLOCK_REALTIME);
-  GPR_ASSERT(ts->acked_time.tv_sec == 123);
-  GPR_ASSERT(ts->acked_time.tv_nsec == 456);
-  gpr_atm* done = reinterpret_cast<gpr_atm*>(arg);
-  gpr_atm_rel_store(done, static_cast<gpr_atm>(1));
-}
-
-/** Tests that the timestamp verifier is called on an ACK timestamp.
- */
-static void TestVerifierCalledOnAck() {
-  struct sock_extended_err serr;
-  serr.ee_data = 213;
-  serr.ee_info = SCM_TSTAMP_ACK;
-  struct scm_timestamping tss;
-  tss.ts[0].tv_sec = 123;
-  tss.ts[0].tv_nsec = 456;
-  grpc_core::grpc_tcp_set_write_timestamps_callback(
-      TestVerifierCalledOnAckVerifier);
-  grpc_core::TracedBuffer* list = nullptr;
-  gpr_atm verifier_called;
-  gpr_atm_rel_store(&verifier_called, static_cast<gpr_atm>(0));
-  grpc_core::TracedBuffer::AddNewEntry(&list, 213, &verifier_called);
-  grpc_core::TracedBuffer::ProcessTimestamp(&list, &serr, &tss);
-  GPR_ASSERT(gpr_atm_acq_load(&verifier_called) == static_cast<gpr_atm>(1));
-  GPR_ASSERT(list == nullptr);
-  grpc_core::TracedBuffer::Shutdown(&list, GRPC_ERROR_NONE);
-}
-
-static void TestTcpBufferList() {
-  TestVerifierCalledOnAck();
-  TestShutdownFlushesList();
-}
-
-int main(int argc, char** argv) {
-  grpc_test_init(argc, argv);
-  grpc_init();
-  TestTcpBufferList();
-  grpc_shutdown();
-  return 0;
-}
-
-#else /* GRPC_LINUX_ERRQUEUE */
-
-int main(int argc, char** argv) { return 0; }
-
-#endif /* GRPC_LINUX_ERRQUEUE */
diff --git a/test/core/iomgr/endpoint_tests.cc b/test/core/iomgr/endpoint_tests.cc
index a9e8ba86c5..8db8ac5ed6 100644
--- a/test/core/iomgr/endpoint_tests.cc
+++ b/test/core/iomgr/endpoint_tests.cc
@@ -150,8 +150,8 @@ static void read_and_write_test_write_handler(void* data, grpc_error* error) {
                                &state->current_write_data);
       grpc_slice_buffer_reset_and_unref(&state->outgoing);
       grpc_slice_buffer_addn(&state->outgoing, slices, nslices);
-      grpc_endpoint_write(state->write_ep, &state->outgoing, &state->done_write,
-                          nullptr);
+      grpc_endpoint_write(state->write_ep, &state->outgoing,
+                          &state->done_write);
       gpr_free(slices);
       return;
     }
@@ -294,8 +294,7 @@ static void multiple_shutdown_test(grpc_endpoint_test_config config) {
   grpc_slice_buffer_add(&slice_buffer, grpc_slice_from_copied_string("a"));
   grpc_endpoint_write(f.client_ep, &slice_buffer,
                       GRPC_CLOSURE_CREATE(inc_on_failure, &fail_count,
-                                          grpc_schedule_on_exec_ctx),
-                      nullptr);
+                                          grpc_schedule_on_exec_ctx));
   wait_for_fail_count(&fail_count, 3);
   grpc_endpoint_shutdown(f.client_ep,
                          GRPC_ERROR_CREATE_FROM_STATIC_STRING("Test Shutdown"));
diff --git a/test/core/iomgr/tcp_posix_test.cc b/test/core/iomgr/tcp_posix_test.cc
index 6447cc234d..3e87831e44 100644
--- a/test/core/iomgr/tcp_posix_test.cc
+++ b/test/core/iomgr/tcp_posix_test.cc
@@ -36,9 +36,6 @@
 #include <grpc/support/time.h>
 
 #include "src/core/lib/gpr/useful.h"
-#include "src/core/lib/iomgr/buffer_list.h"
-#include "src/core/lib/iomgr/ev_posix.h"
-#include "src/core/lib/iomgr/sockaddr_posix.h"
 #include "src/core/lib/slice/slice_internal.h"
 #include "test/core/iomgr/endpoint_tests.h"
 #include "test/core/util/test_config.h"
@@ -71,43 +68,6 @@ static void create_sockets(int sv[2]) {
   GPR_ASSERT(fcntl(sv[1], F_SETFL, flags | O_NONBLOCK) == 0);
 }
 
-static void create_inet_sockets(int sv[2]) {
-  /* Prepare listening socket */
-  struct sockaddr_in addr;
-  memset(&addr, 0, sizeof(struct sockaddr_in));
-  addr.sin_family = AF_INET;
-  int sock = socket(AF_INET, SOCK_STREAM, 0);
-  GPR_ASSERT(sock);
-  GPR_ASSERT(bind(sock, (sockaddr*)&addr, sizeof(sockaddr_in)) == 0);
-  listen(sock, 1);
-
-  /* Prepare client socket and connect to server */
-  socklen_t len = sizeof(sockaddr_in);
-  GPR_ASSERT(getsockname(sock, (sockaddr*)&addr, &len) == 0);
-
-  int client = socket(AF_INET, SOCK_STREAM, 0);
-  GPR_ASSERT(client);
-  int ret;
-  do {
-    ret = connect(client, (sockaddr*)&addr, sizeof(sockaddr_in));
-  } while (ret == -1 && errno == EINTR);
-
-  /* Accept client connection */
-  len = sizeof(socklen_t);
-  int server;
-  do {
-    server = accept(sock, (sockaddr*)&addr, (socklen_t*)&len);
-  } while (server == -1 && errno == EINTR);
-  GPR_ASSERT(server != -1);
-
-  sv[0] = server;
-  sv[1] = client;
-  int flags = fcntl(sv[0], F_GETFL, 0);
-  GPR_ASSERT(fcntl(sv[0], F_SETFL, flags | O_NONBLOCK) == 0);
-  flags = fcntl(sv[1], F_GETFL, 0);
-  GPR_ASSERT(fcntl(sv[1], F_SETFL, flags | O_NONBLOCK) == 0);
-}
-
 static ssize_t fill_socket(int fd) {
   ssize_t write_bytes;
   ssize_t total_bytes = 0;
@@ -329,10 +289,11 @@ static grpc_slice* allocate_blocks(size_t num_bytes, size_t slice_size,
 
 static void write_done(void* user_data /* write_socket_state */,
                        grpc_error* error) {
-  GPR_ASSERT(error == GRPC_ERROR_NONE);
   struct write_socket_state* state =
       static_cast<struct write_socket_state*>(user_data);
+  gpr_log(GPR_INFO, "Write done callback called");
   gpr_mu_lock(g_mu);
+  gpr_log(GPR_INFO, "Signalling write done");
   state->write_done = 1;
   GPR_ASSERT(
       GRPC_LOG_IF_ERROR("pollset_kick", grpc_pollset_kick(g_pollset, nullptr)));
@@ -379,24 +340,10 @@ void drain_socket_blocking(int fd, size_t num_bytes, size_t read_size) {
   gpr_free(buf);
 }
 
-/* Verifier for timestamps callback for write_test */
-void timestamps_verifier(void* arg, grpc_core::Timestamps* ts,
-                         grpc_error* error) {
-  GPR_ASSERT(error == GRPC_ERROR_NONE);
-  GPR_ASSERT(arg != nullptr);
-  GPR_ASSERT(ts->sendmsg_time.clock_type == GPR_CLOCK_REALTIME);
-  GPR_ASSERT(ts->scheduled_time.clock_type == GPR_CLOCK_REALTIME);
-  GPR_ASSERT(ts->acked_time.clock_type == GPR_CLOCK_REALTIME);
-  gpr_atm* done_timestamps = (gpr_atm*)arg;
-  gpr_atm_rel_store(done_timestamps, static_cast<gpr_atm>(1));
-}
-
 /* Write to a socket using the grpc_tcp API, then drain it directly.
    Note that if the write does not complete immediately we need to drain the
-   socket in parallel with the read. If collect_timestamps is true, it will
-   try to get timestamps for the write. */
-static void write_test(size_t num_bytes, size_t slice_size,
-                       bool collect_timestamps) {
+   socket in parallel with the read. */
+static void write_test(size_t num_bytes, size_t slice_size) {
   int sv[2];
   grpc_endpoint* ep;
   struct write_socket_state state;
@@ -409,27 +356,19 @@ static void write_test(size_t num_bytes, size_t slice_size,
       grpc_timespec_to_millis_round_up(grpc_timeout_seconds_to_deadline(20));
   grpc_core::ExecCtx exec_ctx;
 
-  if (collect_timestamps && !grpc_event_engine_can_track_errors()) {
-    return;
-  }
-
   gpr_log(GPR_INFO,
           "Start write test with %" PRIuPTR " bytes, slice size %" PRIuPTR,
           num_bytes, slice_size);
 
-  if (collect_timestamps) {
-    create_inet_sockets(sv);
-  } else {
-    create_sockets(sv);
-  }
+  create_sockets(sv);
 
   grpc_arg a[1];
   a[0].key = const_cast<char*>(GRPC_ARG_TCP_READ_CHUNK_SIZE);
   a[0].type = GRPC_ARG_INTEGER,
   a[0].value.integer = static_cast<int>(slice_size);
   grpc_channel_args args = {GPR_ARRAY_SIZE(a), a};
-  ep = grpc_tcp_create(grpc_fd_create(sv[1], "write_test", collect_timestamps),
-                       &args, "test");
+  ep = grpc_tcp_create(grpc_fd_create(sv[1], "write_test", false), &args,
+                       "test");
   grpc_endpoint_add_to_pollset(ep, g_pollset);
 
   state.ep = ep;
@@ -442,26 +381,18 @@ static void write_test(size_t num_bytes, size_t slice_size,
   GRPC_CLOSURE_INIT(&write_done_closure, write_done, &state,
                     grpc_schedule_on_exec_ctx);
 
-  gpr_atm done_timestamps;
-  gpr_atm_rel_store(&done_timestamps, static_cast<gpr_atm>(0));
-  grpc_endpoint_write(ep, &outgoing, &write_done_closure,
-                      grpc_event_engine_can_track_errors() && collect_timestamps
-                          ? (void*)&done_timestamps
-                          : nullptr);
+  grpc_endpoint_write(ep, &outgoing, &write_done_closure);
   drain_socket_blocking(sv[0], num_bytes, num_bytes);
-  exec_ctx.Flush();
   gpr_mu_lock(g_mu);
   for (;;) {
     grpc_pollset_worker* worker = nullptr;
-    if (state.write_done &&
-        (!(grpc_event_engine_can_track_errors() && collect_timestamps) ||
-         gpr_atm_acq_load(&done_timestamps) == static_cast<gpr_atm>(1))) {
+    if (state.write_done) {
       break;
     }
     GPR_ASSERT(GRPC_LOG_IF_ERROR(
         "pollset_work", grpc_pollset_work(g_pollset, &worker, deadline)));
     gpr_mu_unlock(g_mu);
-    exec_ctx.Flush();
+
     gpr_mu_lock(g_mu);
   }
   gpr_mu_unlock(g_mu);
@@ -566,21 +497,14 @@ void run_tests(void) {
   large_read_test(8192);
   large_read_test(1);
 
-  write_test(100, 8192, false);
-  write_test(100, 1, false);
-  write_test(100000, 8192, false);
-  write_test(100000, 1, false);
-  write_test(100000, 137, false);
-
-  write_test(100, 8192, true);
-  write_test(100, 1, true);
-  write_test(100000, 8192, true);
-  write_test(100000, 1, true);
-  write_test(100, 137, true);
+  write_test(100, 8192);
+  write_test(100, 1);
+  write_test(100000, 8192);
+  write_test(100000, 1);
+  write_test(100000, 137);
 
   for (i = 1; i < 1000; i = GPR_MAX(i + 1, i * 5 / 4)) {
-    write_test(40320, i, false);
-    write_test(40320, i, true);
+    write_test(40320, i);
   }
 
   release_fd_test(100, 8192);
@@ -625,7 +549,6 @@ int main(int argc, char** argv) {
   grpc_closure destroyed;
   grpc_test_init(argc, argv);
   grpc_init();
-  grpc_core::grpc_tcp_set_write_timestamps_callback(timestamps_verifier);
   {
     grpc_core::ExecCtx exec_ctx;
     g_pollset = static_cast<grpc_pollset*>(gpr_zalloc(grpc_pollset_size()));
diff --git a/test/core/tsi/ssl_transport_security_test.cc b/test/core/tsi/ssl_transport_security_test.cc
index b477904d60..baffad6ea3 100644
--- a/test/core/tsi/ssl_transport_security_test.cc
+++ b/test/core/tsi/ssl_transport_security_test.cc
@@ -208,9 +208,11 @@ static void check_session_reusage(ssl_tsi_test_fixture* ssl_fixture,
       tsi_peer_get_property_by_name(peer, TSI_SSL_SESSION_REUSED_PEER_PROPERTY);
   GPR_ASSERT(session_reused != nullptr);
   if (ssl_fixture->session_reused) {
-    GPR_ASSERT(strcmp(session_reused->value.data, "true") == 0);
+    GPR_ASSERT(strncmp(session_reused->value.data, "true",
+                       session_reused->value.length) == 0);
   } else {
-    GPR_ASSERT(strcmp(session_reused->value.data, "false") == 0);
+    GPR_ASSERT(strncmp(session_reused->value.data, "false",
+                       session_reused->value.length) == 0);
   }
 }
 
diff --git a/test/core/util/mock_endpoint.cc b/test/core/util/mock_endpoint.cc
index ef6fd62b51..1156cd5fc5 100644
--- a/test/core/util/mock_endpoint.cc
+++ b/test/core/util/mock_endpoint.cc
@@ -55,7 +55,7 @@ static void me_read(grpc_endpoint* ep, grpc_slice_buffer* slices,
 }
 
 static void me_write(grpc_endpoint* ep, grpc_slice_buffer* slices,
-                     grpc_closure* cb, void* arg) {
+                     grpc_closure* cb) {
   mock_endpoint* m = reinterpret_cast<mock_endpoint*>(ep);
   for (size_t i = 0; i < slices->count; i++) {
     m->on_write(slices->slices[i]);
diff --git a/test/core/util/passthru_endpoint.cc b/test/core/util/passthru_endpoint.cc
index 3cc8ad6fe1..5958216747 100644
--- a/test/core/util/passthru_endpoint.cc
+++ b/test/core/util/passthru_endpoint.cc
@@ -76,7 +76,7 @@ static half* other_half(half* h) {
 }
 
 static void me_write(grpc_endpoint* ep, grpc_slice_buffer* slices,
-                     grpc_closure* cb, void* arg) {
+                     grpc_closure* cb) {
   half* m = other_half(reinterpret_cast<half*>(ep));
   gpr_mu_lock(&m->parent->mu);
   grpc_error* error = GRPC_ERROR_NONE;
diff --git a/test/core/util/trickle_endpoint.cc b/test/core/util/trickle_endpoint.cc
index 62ed72a629..f2efb049b4 100644
--- a/test/core/util/trickle_endpoint.cc
+++ b/test/core/util/trickle_endpoint.cc
@@ -62,7 +62,7 @@ static void maybe_call_write_cb_locked(trickle_endpoint* te) {
 }
 
 static void te_write(grpc_endpoint* ep, grpc_slice_buffer* slices,
-                     grpc_closure* cb, void* arg) {
+                     grpc_closure* cb) {
   trickle_endpoint* te = reinterpret_cast<trickle_endpoint*>(ep);
   gpr_mu_lock(&te->mu);
   GPR_ASSERT(te->write_cb == nullptr);
@@ -186,8 +186,7 @@ size_t grpc_trickle_endpoint_trickle(grpc_endpoint* ep) {
       te->last_write = now;
       grpc_endpoint_write(
           te->wrapped, &te->writing_buffer,
-          GRPC_CLOSURE_CREATE(te_finish_write, te, grpc_schedule_on_exec_ctx),
-          nullptr);
+          GRPC_CLOSURE_CREATE(te_finish_write, te, grpc_schedule_on_exec_ctx));
       maybe_call_write_cb_locked(te);
     }
   }
diff --git a/test/cpp/microbenchmarks/bm_chttp2_transport.cc b/test/cpp/microbenchmarks/bm_chttp2_transport.cc
index 189923a841..1e9bd273aa 100644
--- a/test/cpp/microbenchmarks/bm_chttp2_transport.cc
+++ b/test/cpp/microbenchmarks/bm_chttp2_transport.cc
@@ -96,7 +96,7 @@ class DummyEndpoint : public grpc_endpoint {
   }
 
   static void write(grpc_endpoint* ep, grpc_slice_buffer* slices,
-                    grpc_closure* cb, void* arg) {
+                    grpc_closure* cb) {
     GRPC_CLOSURE_SCHED(cb, GRPC_ERROR_NONE);
   }
 
diff --git a/test/cpp/qps/client.h b/test/cpp/qps/client.h
index 9d7469c9b5..0b4b2ff0a9 100644
--- a/test/cpp/qps/client.h
+++ b/test/cpp/qps/client.h
@@ -180,6 +180,19 @@ class Client {
       timer_result = timer_->Mark();
     }
 
+    // Print the median latency per interval for one thread.
+    // If the number of warmup seconds is x, then the first x + 1 numbers in the
+    // vector are from the warmup period and should be discarded.
+    if (median_latency_collection_interval_seconds_ > 0) {
+      std::vector<double> medians_per_interval =
+          threads_[0]->GetMedianPerIntervalList();
+      gpr_log(GPR_INFO, "Num threads: %ld", threads_.size());
+      gpr_log(GPR_INFO, "Number of medians: %ld", medians_per_interval.size());
+      for (size_t j = 0; j < medians_per_interval.size(); j++) {
+        gpr_log(GPR_INFO, "%f", medians_per_interval[j]);
+      }
+    }
+
     grpc_stats_data core_stats;
     grpc_stats_collect(&core_stats);
 
@@ -210,6 +223,12 @@ class Client {
     }
   }
 
+  // Returns the interval (in seconds) between collecting latency medians. If 0,
+  // no periodic median latencies will be collected.
+  double GetLatencyCollectionIntervalInSeconds() {
+    return median_latency_collection_interval_seconds_;
+  }
+
   virtual int GetPollCount() {
     // For sync client.
     return 0;
@@ -218,6 +237,7 @@ class Client {
  protected:
   bool closed_loop_;
   gpr_atm thread_pool_done_;
+  double median_latency_collection_interval_seconds_;  // In seconds
 
   void StartThreads(size_t num_threads) {
     gpr_atm_rel_store(&thread_pool_done_, static_cast<gpr_atm>(false));
@@ -299,10 +319,27 @@ class Client {
       MergeStatusHistogram(statuses_, s);
     }
 
+    std::vector<double> GetMedianPerIntervalList() {
+      return medians_each_interval_list_;
+    }
+
     void UpdateHistogram(HistogramEntry* entry) {
       std::lock_guard<std::mutex> g(mu_);
       if (entry->value_used()) {
         histogram_.Add(entry->value());
+        if (client_->GetLatencyCollectionIntervalInSeconds() > 0) {
+          histogram_per_interval_.Add(entry->value());
+          double now = UsageTimer::Now();
+          if ((now - interval_start_time_) >=
+              client_->GetLatencyCollectionIntervalInSeconds()) {
+            // Record the median latency of requests from the last interval.
+            // Divide by 1e3 to get microseconds.
+            medians_each_interval_list_.push_back(
+                histogram_per_interval_.Percentile(50) / 1e3);
+            histogram_per_interval_.Reset();
+            interval_start_time_ = now;
+          }
+        }
       }
       if (entry->status_used()) {
         statuses_[entry->status()]++;
@@ -334,6 +371,11 @@ class Client {
     Client* client_;
     const size_t idx_;
     std::thread impl_;
+    // The following are used only if
+    // median_latency_collection_interval_seconds_ is greater than 0
+    Histogram histogram_per_interval_;
+    std::vector<double> medians_each_interval_list_;
+    double interval_start_time_;
   };
 
   bool ThreadCompleted() {
@@ -392,7 +434,8 @@ class ClientImpl : public Client {
     for (auto& t : connecting_threads) {
       t->join();
     }
-
+    median_latency_collection_interval_seconds_ =
+        config.median_latency_collection_interval_millis() / 1e3;
     ClientRequestCreator<RequestType> create_req(&request_,
                                                  config.payload_config());
   }
diff --git a/test/cpp/qps/driver.cc b/test/cpp/qps/driver.cc
index cabbd51843..11cfb4aa05 100644
--- a/test/cpp/qps/driver.cc
+++ b/test/cpp/qps/driver.cc
@@ -198,7 +198,8 @@ std::unique_ptr<ScenarioResult> RunScenario(
     const ServerConfig& initial_server_config, size_t num_servers,
     int warmup_seconds, int benchmark_seconds, int spawn_local_worker_count,
     const grpc::string& qps_server_target_override,
-    const grpc::string& credential_type, bool run_inproc) {
+    const grpc::string& credential_type, bool run_inproc,
+    int32_t median_latency_collection_interval_millis) {
   if (run_inproc) {
     g_inproc_servers = new std::vector<grpc::testing::Server*>;
   }
@@ -317,6 +318,9 @@ std::unique_ptr<ScenarioResult> RunScenario(
     }
   }
 
+  client_config.set_median_latency_collection_interval_millis(
+      median_latency_collection_interval_millis);
+
   // Targets are all set by now
   result_client_config = client_config;
   // Start clients
diff --git a/test/cpp/qps/driver.h b/test/cpp/qps/driver.h
index fede4d8045..cda89f7ddf 100644
--- a/test/cpp/qps/driver.h
+++ b/test/cpp/qps/driver.h
@@ -32,7 +32,8 @@ std::unique_ptr<ScenarioResult> RunScenario(
     const grpc::testing::ServerConfig& server_config, size_t num_servers,
     int warmup_seconds, int benchmark_seconds, int spawn_local_worker_count,
     const grpc::string& qps_server_target_override,
-    const grpc::string& credential_type, bool run_inproc);
+    const grpc::string& credential_type, bool run_inproc,
+    int32_t median_latency_collection_interval_millis);
 
 bool RunQuit(const grpc::string& credential_type);
 }  // namespace testing
diff --git a/test/cpp/qps/histogram.h b/test/cpp/qps/histogram.h
index ba72b5b332..6275128f34 100644
--- a/test/cpp/qps/histogram.h
+++ b/test/cpp/qps/histogram.h
@@ -34,6 +34,11 @@ class Histogram {
   ~Histogram() {
     if (impl_) grpc_histogram_destroy(impl_);
   }
+  void Reset() {
+    if (impl_) grpc_histogram_destroy(impl_);
+    impl_ = grpc_histogram_create(default_resolution(), default_max_possible());
+  }
+
   Histogram(Histogram&& other) : impl_(other.impl_) { other.impl_ = nullptr; }
 
   void Merge(const Histogram& h) { grpc_histogram_merge(impl_, h.impl_); }
diff --git a/test/cpp/qps/inproc_sync_unary_ping_pong_test.cc b/test/cpp/qps/inproc_sync_unary_ping_pong_test.cc
index f2e977d48b..56d1730252 100644
--- a/test/cpp/qps/inproc_sync_unary_ping_pong_test.cc
+++ b/test/cpp/qps/inproc_sync_unary_ping_pong_test.cc
@@ -48,7 +48,7 @@ static void RunSynchronousUnaryPingPong() {
 
   const auto result =
       RunScenario(client_config, 1, server_config, 1, WARMUP, BENCHMARK, -2, "",
-                  kInsecureCredentialsType, true);
+                  kInsecureCredentialsType, true, 0);
 
   GetReporter()->ReportQPS(*result);
   GetReporter()->ReportLatency(*result);
diff --git a/test/cpp/qps/qps_json_driver.cc b/test/cpp/qps/qps_json_driver.cc
index 0ff692255c..eaa0dd992c 100644
--- a/test/cpp/qps/qps_json_driver.cc
+++ b/test/cpp/qps/qps_json_driver.cc
@@ -66,6 +66,11 @@ DEFINE_string(json_file_out, "", "File to write the JSON output to.");
 DEFINE_string(credential_type, grpc::testing::kInsecureCredentialsType,
               "Credential type for communication with workers");
 DEFINE_bool(run_inproc, false, "Perform an in-process transport test");
+DEFINE_int32(
+    median_latency_collection_interval_millis, 0,
+    "Specifies the period between gathering latency medians in "
+    "milliseconds. The medians will be logged out on the client at the "
+    "end of the benchmark run. If 0, this periodic collection is disabled.");
 
 namespace grpc {
 namespace testing {
@@ -73,13 +78,13 @@ namespace testing {
 static std::unique_ptr<ScenarioResult> RunAndReport(const Scenario& scenario,
                                                     bool* success) {
   std::cerr << "RUNNING SCENARIO: " << scenario.name() << "\n";
-  auto result =
-      RunScenario(scenario.client_config(), scenario.num_clients(),
-                  scenario.server_config(), scenario.num_servers(),
-                  scenario.warmup_seconds(), scenario.benchmark_seconds(),
-                  !FLAGS_run_inproc ? scenario.spawn_local_worker_count() : -2,
-                  FLAGS_qps_server_target_override, FLAGS_credential_type,
-                  FLAGS_run_inproc);
+  auto result = RunScenario(
+      scenario.client_config(), scenario.num_clients(),
+      scenario.server_config(), scenario.num_servers(),
+      scenario.warmup_seconds(), scenario.benchmark_seconds(),
+      !FLAGS_run_inproc ? scenario.spawn_local_worker_count() : -2,
+      FLAGS_qps_server_target_override, FLAGS_credential_type, FLAGS_run_inproc,
+      FLAGS_median_latency_collection_interval_millis);
 
   // Amend the result with scenario config. Eventually we should adjust
   // RunScenario contract so we don't need to touch the result here.
diff --git a/test/cpp/qps/qps_openloop_test.cc b/test/cpp/qps/qps_openloop_test.cc
index df929b9811..6044f4265a 100644
--- a/test/cpp/qps/qps_openloop_test.cc
+++ b/test/cpp/qps/qps_openloop_test.cc
@@ -52,7 +52,7 @@ static void RunQPS() {
 
   const auto result =
       RunScenario(client_config, 1, server_config, 1, WARMUP, BENCHMARK, -2, "",
-                  kInsecureCredentialsType, false);
+                  kInsecureCredentialsType, false, 0);
 
   GetReporter()->ReportQPSPerCore(*result);
   GetReporter()->ReportLatency(*result);
diff --git a/test/cpp/qps/secure_sync_unary_ping_pong_test.cc b/test/cpp/qps/secure_sync_unary_ping_pong_test.cc
index bb415e9d63..a559c82cc8 100644
--- a/test/cpp/qps/secure_sync_unary_ping_pong_test.cc
+++ b/test/cpp/qps/secure_sync_unary_ping_pong_test.cc
@@ -55,7 +55,7 @@ static void RunSynchronousUnaryPingPong() {
 
   const auto result =
       RunScenario(client_config, 1, server_config, 1, WARMUP, BENCHMARK, -2, "",
-                  kInsecureCredentialsType, false);
+                  kInsecureCredentialsType, false, 0);
 
   GetReporter()->ReportQPS(*result);
   GetReporter()->ReportLatency(*result);