conn pool: fixing overly aggressive connect

source/common/conn_pool/conn_pool_base.cc

@@ -106,6 +106,7 @@ float ConnPoolImplBase::perUpstreamPreconnectRatio() const {
 }
 
 ConnPoolImplBase::ConnectionResult ConnPoolImplBase::tryCreateNewConnections() {
+  ASSERT(!is_draining_for_deletion_);
   ConnPoolImplBase::ConnectionResult result;
   // Somewhat arbitrarily cap the number of connections preconnected due to new
   // incoming connections. The preconnect ratio is capped at 3, so in steady
@@ -462,7 +463,9 @@ void ConnPoolImplBase::onConnectionEvent(ActiveClient& client, absl::string_view
       //       if retry logic submits a new stream to the pool, we don't fail it inline.
       purgePendingStreams(client.real_host_description_, failure_reason, reason);
       // See if we should preconnect based on active connections.
-      tryCreateNewConnections();
+      if (!is_draining_for_deletion_) {
+        tryCreateNewConnections();
+      }
     }
 
     // We need to release our resourceManager() resources before checking below for

test/integration/cds_integration_test.cc

@@ -182,6 +182,32 @@ TEST_P(CdsIntegrationTest, CdsClusterUpDownUp) {
   cleanupUpstreamAndDownstream();
 }
 
+// Make sure that clusters won't create new connections on teardown.
+TEST_P(CdsIntegrationTest, CdsClusterTeardownWhileConnecting) {
+  initialize();
+  test_server_->waitForCounterGe("cluster_manager.cluster_added", 1);
+
+  // Make the upstreams stop working, to ensure the connection was not
+  // established.
+  fake_upstreams_[1]->dispatcher()->exit();
+  fake_upstreams_[2]->dispatcher()->exit();
+  codec_client_ = makeHttpConnection(lookupPort("http"));
+  auto encoder_decoder = codec_client_->startRequest(Http::TestRequestHeaderMapImpl{
+      {":method", "GET"}, {":path", "/cluster1"}, {":scheme", "http"}, {":authority", "host"}});
+
+  // Tell Envoy that cluster_1 is gone.
+  EXPECT_TRUE(compareDiscoveryRequest(Config::TypeUrl::get().Cluster, "55", {}, {}, {}));
+  sendDiscoveryResponse<envoy::config::cluster::v3::Cluster>(Config::TypeUrl::get().Cluster, {}, {},
+                                                             {ClusterName1}, "42");
+  // We can continue the test once we're sure that Envoy's ClusterManager has made use of
+  // the DiscoveryResponse that says cluster_1 is gone.
+  test_server_->waitForCounterGe("cluster_manager.cluster_removed", 1);
+  codec_client_->sendReset(encoder_decoder.first);
+  cleanupUpstreamAndDownstream();
+  // Make sure there was only one connection attempt.
+  EXPECT_LE(test_server_->counter("cluster.cluster_1.upstream_cx_total")->value(), 1);
+}
+
 // Test the fast addition and removal of clusters when they use ThreadAwareLb.
 TEST_P(CdsIntegrationTest, CdsClusterWithThreadAwareLbCycleUpDownUp) {
   // Calls our initialize(), which includes establishing a listener, route, and cluster.

tools/base/envoy_python.bzl

@@ -1,4 +1,4 @@
-load("@rules_python//python:defs.bzl", "py_binary", "py_library")
+load("@rules_python//python:defs.bzl", "py_binary")
 load("@base_pip3//:requirements.bzl", base_entry_point = "entry_point")
 
 def envoy_py_test(name, package, visibility, envoy_prefix = "@envoy"):