Fix re-resolution in pick_first

1 files changed, 38 insertions, 2 deletions

diff --git a/test/cpp/end2end/client_lb_end2end_test.cc b/test/cpp/end2end/client_lb_end2end_test.cc
index 8896fc6cae..c5a73a2469 100644
--- a/test/cpp/end2end/client_lb_end2end_test.cc
+++ b/test/cpp/end2end/client_lb_end2end_test.cc
@@ -279,9 +279,14 @@ class ClientLbEnd2endTest : public ::testing::Test {
 
   void WaitForServer(
       const std::unique_ptr<grpc::testing::EchoTestService::Stub>& stub,
-      size_t server_idx, const grpc_core::DebugLocation& location) {
+      size_t server_idx, const grpc_core::DebugLocation& location,
+      bool ignore_failure = false) {
     do {
-      CheckRpcSendOk(stub, location);
+      if (ignore_failure) {
+        SendRpc(stub);
+      } else {
+        CheckRpcSendOk(stub, location);
+      }
     } while (servers_[server_idx]->service_.request_count() == 0);
     ResetCounters();
   }
@@ -507,6 +512,37 @@ TEST_F(ClientLbEnd2endTest, PickFirstManyUpdates) {
   EXPECT_EQ("pick_first", channel->GetLoadBalancingPolicyName());
 }
 
+TEST_F(ClientLbEnd2endTest, PickFirstReresolutionNoSelected) {
+  // Prepare the ports for up servers and down servers.
+  const int kNumServers = 3;
+  const int kNumAliveServers = 1;
+  StartServers(kNumAliveServers);
+  std::vector<int> alive_ports, dead_ports;
+  for (size_t i = 0; i < kNumServers; ++i) {
+    if (i < kNumAliveServers) {
+      alive_ports.emplace_back(servers_[i]->port_);
+    } else {
+      dead_ports.emplace_back(grpc_pick_unused_port_or_die());
+    }
+  }
+  auto channel = BuildChannel("pick_first");
+  auto stub = BuildStub(channel);
+  // The initial resolution only contains dead ports. There won't be any
+  // selected subchannel. Re-resolution will return the same result.
+  SetNextResolution(dead_ports);
+  gpr_log(GPR_INFO, "****** INITIAL RESOLUTION SET *******");
+  for (size_t i = 0; i < 10; ++i) CheckRpcSendFailure(stub);
+  // Set a re-resolution result that contains reachable ports, so that the
+  // pick_first LB policy can recover soon.
+  SetNextResolutionUponError(alive_ports);
+  gpr_log(GPR_INFO, "****** RE-RESOLUTION SET *******");
+  WaitForServer(stub, 0, DEBUG_LOCATION, true /* ignore_failure */);
+  CheckRpcSendOk(stub, DEBUG_LOCATION);
+  EXPECT_EQ(servers_[0]->service_.request_count(), 1);
+  // Check LB policy name for the channel.
+  EXPECT_EQ("pick_first", channel->GetLoadBalancingPolicyName());
+}
+
 TEST_F(ClientLbEnd2endTest, RoundRobin) {
   // Start servers and send one RPC per server.
   const int kNumServers = 3;