alpn: adding a connection fail test (envoyproxy#31965)

Signed-off-by: Alyssa Wilk <alyssar@chromium.org>

test/integration/BUILD

@@ -82,6 +82,7 @@ envoy_cc_test(
     name = "alpn_integration_test",
     size = "large",
     srcs = ["alpn_integration_test.cc"],
+    shard_count = 2,
     tags = [
         "cpu:3",
     ],

test/integration/alpn_integration_test.cc

@@ -185,5 +185,34 @@ TEST_P(AlpnIntegrationTest, Mixed) {
   EXPECT_EQ("200", response2->headers().Status()->value().getStringView());
 }
 
+TEST_P(AlpnIntegrationTest, DisconnectDuringHandshake) {
+  DISABLE_UNDER_WINDOWS;
+  setUpstreamProtocol(Http::CodecType::HTTP2);
+  protocols_ = {Http::CodecType::HTTP2};
+  setUpstreamCount(1);
+  initialize();
+
+  absl::Notification unblock_accept;
+  absl::Notification accept_blocked;
+  fake_upstreams_[0]->runOnDispatcherThread([&] {
+    accept_blocked.Notify();
+    unblock_accept.WaitForNotification();
+  });
+  accept_blocked.WaitForNotification();
+
+  // Connect and wait for the upstream connection to be established.
+  codec_client_ = makeHttpConnection(makeClientConnection((lookupPort("http"))));
+  auto response = codec_client_->makeHeaderOnlyRequest(default_request_headers_);
+  test_server_->waitForCounterGe("cluster.cluster_0.upstream_cx_total", 1);
+
+  // Close the downstream connection and wait for the upstream stream to go away.
+  codec_client_->close();
+  test_server_->waitForCounterEq("cluster.cluster_0.upstream_rq_cancelled", 1);
+
+  // Allow the connection to complete.
+  unblock_accept.Notify();
+  test_server_->waitForCounterGe("cluster.cluster_0.upstream_cx_http2_total", 1);
+}
+
 } // namespace
 } // namespace Envoy