http: reinstating prior connect timeout behavior

docs/root/version_history/current.rst

@@ -22,6 +22,7 @@ Bug Fixes
 
 * active http health checks: properly handles HTTP/2 GOAWAY frames from the upstream. Previously a GOAWAY frame due to a graceful listener drain could cause improper failed health checks due to streams being refused by the upstream on a connection that is going away. To revert to old GOAWAY handling behavior, set the runtime feature `envoy.reloadable_features.health_check.graceful_goaway_handling` to false.
 * buffer: tighten network connection read and write buffer high watermarks in preparation to more careful enforcement of read limits. Buffer high-watermark is now set to the exact configured value; previously it was set to value + 1.
+* http: reverting a behavioral change where upstream connect timeouts were temporarily treated differently from other connection failures. The change back to the original behavior can be temporarily reverted by setting `envoy.reloadable_features.treat_upstream_connect_timeout_as_connect_failure` to false.
 * upstream: fix handling of moving endpoints between priorities when active health checks are enabled. Previously moving to a higher numbered priority was a NOOP, and moving to a lower numbered priority caused an abort.
 
 Removed Config or Runtime

source/common/router/upstream_request.cc

@@ -337,7 +337,12 @@ void UpstreamRequest::onPoolFailure(ConnectionPool::PoolFailureReason reason,
     reset_reason = Http::StreamResetReason::ConnectionFailure;
     break;
   case ConnectionPool::PoolFailureReason::Timeout:
-    reset_reason = Http::StreamResetReason::LocalReset;
+    if (Runtime::runtimeFeatureEnabled(
+            "envoy.reloadable_features.treat_upstream_connect_timeout_as_connect_failure")) {
+      reset_reason = Http::StreamResetReason::ConnectionFailure;
+    } else {
+      reset_reason = Http::StreamResetReason::LocalReset;
+    }
   }
 
   // Mimic an upstream reset.

source/common/runtime/runtime_features.cc

@@ -85,6 +85,7 @@ constexpr const char* runtime_features[] = {
     "envoy.reloadable_features.stop_faking_paths",
     "envoy.reloadable_features.strict_1xx_and_204_response_headers",
     "envoy.reloadable_features.tls_use_io_handle_bio",
+    "envoy.reloadable_features.treat_upstream_connect_timeout_as_connect_failure",
     "envoy.reloadable_features.upstream_host_weight_change_causes_rebuild",
     "envoy.reloadable_features.vhds_heartbeats",
     "envoy.reloadable_features.unify_grpc_handling",

test/common/router/router_test.cc

@@ -555,6 +555,78 @@ TEST_F(RouterTest, PoolFailureWithPriority) {
             "upstream_reset_before_response_started{connection failure,tls version mismatch}");
 }
 
+TEST_F(RouterTest, PoolFailureDueToConnectTimeout) {
+  ON_CALL(callbacks_.route_->route_entry_, priority())
+      .WillByDefault(Return(Upstream::ResourcePriority::High));
+  EXPECT_CALL(cm_.thread_local_cluster_,
+              httpConnPool(Upstream::ResourcePriority::High, _, &router_));
+  EXPECT_CALL(cm_.thread_local_cluster_.conn_pool_, newStream(_, _))
+      .WillOnce(Invoke([&](Http::StreamDecoder&, Http::ConnectionPool::Callbacks& callbacks)
+                           -> Http::ConnectionPool::Cancellable* {
+        callbacks.onPoolFailure(ConnectionPool::PoolFailureReason::Timeout, "connect_timeout",
+                                cm_.thread_local_cluster_.conn_pool_.host_);
+        return nullptr;
+      }));
+
+  Http::TestResponseHeaderMapImpl response_headers{
+      {":status", "503"}, {"content-length", "134"}, {"content-type", "text/plain"}};
+  EXPECT_CALL(callbacks_, encodeHeaders_(HeaderMapEqualRef(&response_headers), false));
+  EXPECT_CALL(callbacks_, encodeData(_, true));
+  EXPECT_CALL(callbacks_.stream_info_,
+              setResponseFlag(StreamInfo::ResponseFlag::UpstreamConnectionFailure));
+  EXPECT_CALL(callbacks_.stream_info_, onUpstreamHostSelected(_))
+      .WillOnce(Invoke([&](const Upstream::HostDescriptionConstSharedPtr host) -> void {
+        EXPECT_EQ(host_address_, host->address());
+      }));
+
+  Http::TestRequestHeaderMapImpl headers;
+  HttpTestUtility::addDefaultHeaders(headers);
+  router_.decodeHeaders(headers, true);
+  EXPECT_TRUE(verifyHostUpstreamStats(0, 1));
+  // Pool failure, so upstream request was not initiated.
+  EXPECT_EQ(0U,
+            callbacks_.route_->route_entry_.virtual_cluster_.stats().upstream_rq_total_.value());
+  EXPECT_EQ(callbacks_.details(),
+            "upstream_reset_before_response_started{connection failure,connect_timeout}");
+}
+
+TEST_F(RouterTest, PoolFailureDueToConnectTimeoutLegacy) {
+  TestScopedRuntime scoped_runtime;
+  Runtime::LoaderSingleton::getExisting()->mergeValues(
+      {{"envoy.reloadable_features.treat_upstream_connect_timeout_as_connect_failure", "false"}});
+  ON_CALL(callbacks_.route_->route_entry_, priority())
+      .WillByDefault(Return(Upstream::ResourcePriority::High));
+  EXPECT_CALL(cm_.thread_local_cluster_,
+              httpConnPool(Upstream::ResourcePriority::High, _, &router_));
+  EXPECT_CALL(cm_.thread_local_cluster_.conn_pool_, newStream(_, _))
+      .WillOnce(Invoke([&](Http::StreamDecoder&, Http::ConnectionPool::Callbacks& callbacks)
+                           -> Http::ConnectionPool::Cancellable* {
+        callbacks.onPoolFailure(ConnectionPool::PoolFailureReason::Timeout, "connect_timeout",
+                                cm_.thread_local_cluster_.conn_pool_.host_);
+        return nullptr;
+      }));
+
+  Http::TestResponseHeaderMapImpl response_headers{
+      {":status", "503"}, {"content-length", "127"}, {"content-type", "text/plain"}};
+  EXPECT_CALL(callbacks_, encodeHeaders_(HeaderMapEqualRef(&response_headers), false));
+  EXPECT_CALL(callbacks_, encodeData(_, true));
+  EXPECT_CALL(callbacks_.stream_info_, setResponseFlag(StreamInfo::ResponseFlag::LocalReset));
+  EXPECT_CALL(callbacks_.stream_info_, onUpstreamHostSelected(_))
+      .WillOnce(Invoke([&](const Upstream::HostDescriptionConstSharedPtr host) -> void {
+        EXPECT_EQ(host_address_, host->address());
+      }));
+
+  Http::TestRequestHeaderMapImpl headers;
+  HttpTestUtility::addDefaultHeaders(headers);
+  router_.decodeHeaders(headers, true);
+  EXPECT_TRUE(verifyHostUpstreamStats(0, 1));
+  // Pool failure, so upstream request was not initiated.
+  EXPECT_EQ(0U,
+            callbacks_.route_->route_entry_.virtual_cluster_.stats().upstream_rq_total_.value());
+  EXPECT_EQ(callbacks_.details(),
+            "upstream_reset_before_response_started{local reset,connect_timeout}");
+}
+
 TEST_F(RouterTest, Http1Upstream) {
   EXPECT_CALL(cm_.thread_local_cluster_, httpConnPool(_, absl::optional<Http::Protocol>(), _));
   EXPECT_CALL(cm_.thread_local_cluster_.conn_pool_, newStream(_, _))