1 files changed, 41 insertions, 10 deletions

diff --git a/test/cpp/end2end/client_lb_end2end_test.cc b/test/cpp/end2end/client_lb_end2end_test.cc
index 54408db600..c236f76e89 100644
--- a/test/cpp/end2end/client_lb_end2end_test.cc
+++ b/test/cpp/end2end/client_lb_end2end_test.cc
@@ -226,6 +226,31 @@ class ClientLbEnd2endTest : public ::testing::Test {
     ResetCounters();
   }
 
+  bool SeenAllServers() {
+    for (const auto& server : servers_) {
+      if (server->service_.request_count() == 0) return false;
+    }
+    return true;
+  }
+
+  // Updates \a connection_order by appending to it the index of the newly
+  // connected server. Must be called after every single RPC.
+  void UpdateConnectionOrder(
+      const std::vector<std::unique_ptr<ServerData>>& servers,
+      std::vector<int>* connection_order) {
+    for (size_t i = 0; i < servers.size(); ++i) {
+      if (servers[i]->service_.request_count() == 1) {
+        // Was the server index known? If not, update connection_order.
+        const auto it =
+            std::find(connection_order->begin(), connection_order->end(), i);
+        if (it == connection_order->end()) {
+          connection_order->push_back(i);
+          return;
+        }
+      }
+    }
+  }
+
   const grpc::string server_host_;
   std::shared_ptr<Channel> channel_;
   std::unique_ptr<grpc::testing::EchoTestService::Stub> stub_;
@@ -370,13 +395,23 @@ TEST_F(ClientLbEnd2endTest, RoundRobin) {
     ports.emplace_back(server->port_);
   }
   SetNextResolution(ports);
-  for (size_t i = 0; i < servers_.size(); ++i) {
+  // Wait until all backends are ready.
+  do {
     CheckRpcSendOk();
-  }
-  // One request should have gone to each server.
+  } while (!SeenAllServers());
+  ResetCounters();
+  // "Sync" to the end of the list. Next sequence of picks will start at the
+  // first server (index 0).
+  WaitForServer(servers_.size() - 1);
+  std::vector<int> connection_order;
   for (size_t i = 0; i < servers_.size(); ++i) {
-    EXPECT_EQ(1, servers_[i]->service_.request_count());
+    CheckRpcSendOk();
+    UpdateConnectionOrder(servers_, &connection_order);
   }
+  // Backends should be iterated over in the order in which the addresses were
+  // given.
+  const auto expected = std::vector<int>{0, 1, 2};
+  EXPECT_EQ(expected, connection_order);
   // Check LB policy name for the channel.
   EXPECT_EQ("round_robin", channel_->GetLoadBalancingPolicyName());
 }
@@ -529,13 +564,9 @@ TEST_F(ClientLbEnd2endTest, RoundRobinReresolve) {
   StartServers(kNumServers, ports);
   ResetStub("round_robin");
   SetNextResolution(ports);
-  // Send one RPC per backend and make sure they are used in order.
-  // Note: This relies on the fact that the subchannels are reported in
-  // state READY in the order in which the addresses are specified,
-  // which is only true because the backends are all local.
-  for (size_t i = 0; i < servers_.size(); ++i) {
+  // Send a number of RPCs, which succeed.
+  for (size_t i = 0; i < 100; ++i) {
     CheckRpcSendOk();
-    EXPECT_EQ(1, servers_[i]->service_.request_count()) << "for backend #" << i;
   }
   // Kill all servers
   for (size_t i = 0; i < servers_.size(); ++i) {