BG-poll very frequently to pick up subchannels's updates in LB tests

test/cpp/end2end/client_lb_end2end_test.cc

@@ -36,6 +36,7 @@
 extern "C" {
 #include "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h"
 #include "src/core/ext/filters/client_channel/subchannel_index.h"
+#include "src/core/lib/support/env.h"
 }
 
 #include "src/proto/grpc/testing/echo.grpc.pb.h"
@@ -86,7 +87,11 @@ class MyTestServiceImpl : public TestServiceImpl {
 class ClientLbEnd2endTest : public ::testing::Test {
  protected:
   ClientLbEnd2endTest()
-      : server_host_("localhost"), kRequestMessage_("Live long and prosper.") {}
+      : server_host_("localhost"), kRequestMessage_("Live long and prosper.") {
+    // Make the backup poller poll very frequently in order to pick up
+    // updates from all the subchannels's FDs.
+    gpr_setenv("GRPC_CLIENT_CHANNEL_BACKUP_POLL_INTERVAL_MS", "1");
+  }
 
   void SetUp() override {
     response_generator_ = grpc_fake_resolver_response_generator_create();

test/cpp/end2end/grpclb_end2end_test.cc

@@ -36,6 +36,7 @@
 extern "C" {
 #include "src/core/ext/filters/client_channel/resolver/fake/fake_resolver.h"
 #include "src/core/lib/iomgr/sockaddr.h"
+#include "src/core/lib/support/env.h"
 }
 
 #include "test/core/util/port.h"
@@ -74,9 +75,9 @@ extern "C" {
 
 using std::chrono::system_clock;
 
+using grpc::lb::v1::LoadBalancer;
 using grpc::lb::v1::LoadBalanceRequest;
 using grpc::lb::v1::LoadBalanceResponse;
-using grpc::lb::v1::LoadBalancer;
 
 namespace grpc {
 namespace testing {
@@ -332,7 +333,11 @@ class GrpclbEnd2endTest : public ::testing::Test {
         num_backends_(num_backends),
         num_balancers_(num_balancers),
         client_load_reporting_interval_seconds_(
-            client_load_reporting_interval_seconds) {}
+            client_load_reporting_interval_seconds) {
+    // Make the backup poller poll very frequently in order to pick up
+    // updates from all the subchannels's FDs.
+    gpr_setenv("GRPC_CLIENT_CHANNEL_BACKUP_POLL_INTERVAL_MS", "1");
+  }
 
   void SetUp() override {
     response_generator_ = grpc_fake_resolver_response_generator_create();

test/cpp/grpclb/grpclb_test.cc

@@ -42,6 +42,7 @@ extern "C" {
 #include "src/core/lib/channel/channel_stack.h"
 #include "src/core/lib/iomgr/sockaddr.h"
 #include "src/core/lib/security/credentials/fake/fake_credentials.h"
+#include "src/core/lib/support/env.h"
 #include "src/core/lib/support/string.h"
 #include "src/core/lib/support/tmpfile.h"
 #include "src/core/lib/surface/channel.h"
@@ -790,6 +791,9 @@ TEST(GrpclbTest, InvalidAddressInServerlist) {}
 int main(int argc, char **argv) {
   ::testing::InitGoogleTest(&argc, argv);
   grpc_test_init(argc, argv);
+  // Make the backup poller poll very frequently in order to pick up
+  // updates from all the subchannels's FDs.
+  gpr_setenv("GRPC_CLIENT_CHANNEL_BACKUP_POLL_INTERVAL_MS", "1");
   grpc_init();
   const auto result = RUN_ALL_TESTS();
   grpc_shutdown();