API: Add Overload Manager ResetReason and ResponseFlag.

api/envoy/config/accesslog/v3/accesslog.proto

@@ -246,6 +246,7 @@ message ResponseFlagFilter {
         in: "DT"
         in: "UPE"
         in: "NC"
+        in: "OM"
       }
     }
   }];

api/envoy/data/accesslog/v3/accesslog.proto

@@ -186,7 +186,7 @@ message AccessLogCommon {
 }
 
 // Flags indicating occurrences during request/response processing.
-// [#next-free-field: 26]
+// [#next-free-field: 27]
 message ResponseFlags {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.data.accesslog.v2.ResponseFlags";
@@ -281,6 +281,9 @@ message ResponseFlags {
 
   // Indicates no cluster was found for the request.
   bool no_cluster_found = 25;
+
+  // Indicates overload manager terminated the request.
+  bool overload_manager = 26;
 }
 
 // Properties of a negotiated TLS connection.

docs/root/configuration/observability/access_log/usage.rst

@@ -323,6 +323,7 @@ The following command operators are supported:
     * **DPE**: The downstream request had an HTTP protocol error.
     * **UPE**: The upstream response had an HTTP protocol error.
     * **UMSDR**: The upstream request reached to max stream duration.
+    * **OM**: Overload Manager terminated the request.
 
 %ROUTE_NAME%
   Name of the route.

docs/root/version_history/current.rst

@@ -78,6 +78,7 @@ Removed Config or Runtime
 New Features
 ------------
 
+* access_log: added the new response flag for :ref:`overload manager termination <envoy_v3_api_field_data.accesslog.v3.ResponseFlags.overload_manager>`. The response flag will be set when the http stream is terminated by overload manager.
 * admission control: added :ref:`admission control <envoy_v3_api_field_extensions.filters.http.admission_control.v3alpha.AdmissionControl.rps_threshold>` option that when average RPS of the sampling window is below this threshold, the filter will not throttle requests. Added :ref:`admission control <envoy_v3_api_field_extensions.filters.http.admission_control.v3alpha.AdmissionControl.max_rejection_probability>` option to set an upper limit on the probability of rejection.
 * bandwidth_limit: added new :ref:`HTTP bandwidth limit filter <config_http_filters_bandwidth_limit>`.
 * bootstrap: added :ref:`dns_resolution_config <envoy_v3_api_field_config.bootstrap.v3.Bootstrap.dns_resolution_config>` to aggregate all of the DNS resolver configuration in a single message. By setting one such configuration option *no_default_search_domain* as true the DNS resolver will not use the default search domains. And by setting the configuration *resolvers* we can specify the external DNS servers to be used for external DNS query.

envoy/http/codec.h

@@ -284,7 +284,9 @@ enum class StreamResetReason {
   // Either there was an early TCP error for a CONNECT request or the peer reset with CONNECT_ERROR
   ConnectError,
   // Received payload did not conform to HTTP protocol.
-  ProtocolError
+  ProtocolError,
+  // If the stream was locally reset by the Overload Manager.
+  OverloadManager
 };
 
 /**

envoy/stream_info/stream_info.h

@@ -86,8 +86,10 @@ enum ResponseFlag {
   UpstreamProtocolError = 0x800000,
   // No cluster found for a given request.
   NoClusterFound = 0x1000000,
+  // Overload Manager terminated the stream.
+  OverloadManager = 0x2000000,
   // ATTENTION: MAKE SURE THIS REMAINS EQUAL TO THE LAST FLAG.
-  LastFlag = NoClusterFound,
+  LastFlag = OverloadManager,
 };
 
 /**

source/common/http/conn_pool_base.cc

@@ -154,6 +154,7 @@ void MultiplexedActiveClientBase::onStreamReset(Http::StreamResetReason reason)
     break;
   case StreamResetReason::LocalReset:
   case StreamResetReason::ProtocolError:
+  case StreamResetReason::OverloadManager:
     parent_.host()->cluster().stats().upstream_rq_tx_reset_.inc();
     break;
   case StreamResetReason::RemoteReset:

source/common/http/utility.cc

@@ -847,6 +847,8 @@ const std::string Utility::resetReasonToString(const Http::StreamResetReason res
     return "remote error with CONNECT request";
   case Http::StreamResetReason::ProtocolError:
     return "protocol error";
+  case Http::StreamResetReason::OverloadManager:
+    return "overload manager reset";
   }
 
   NOT_REACHED_GCOVR_EXCL_LINE;

source/common/router/router.cc

@@ -1144,6 +1144,8 @@ Filter::streamResetReasonToResponseFlag(Http::StreamResetReason reset_reason) {
     return StreamInfo::ResponseFlag::UpstreamRemoteReset;
   case Http::StreamResetReason::ProtocolError:
     return StreamInfo::ResponseFlag::UpstreamProtocolError;
+  case Http::StreamResetReason::OverloadManager:
+    return StreamInfo::ResponseFlag::OverloadManager;
   }
 
   NOT_REACHED_GCOVR_EXCL_LINE;

source/common/stream_info/utility.cc

@@ -21,7 +21,7 @@ const std::string ResponseFlagUtils::toShortString(const StreamInfo& stream_info
 }
 
 absl::flat_hash_map<std::string, ResponseFlag> ResponseFlagUtils::getFlagMap() {
-  static_assert(ResponseFlag::LastFlag == 0x1000000,
+  static_assert(ResponseFlag::LastFlag == 0x2000000,
                 "A flag has been added. Add the new flag to ALL_RESPONSE_STRING_FLAGS.");
   absl::flat_hash_map<std::string, ResponseFlag> res;
   for (auto [str, flag] : ResponseFlagUtils::ALL_RESPONSE_STRING_FLAGS) {

source/common/stream_info/utility.h

@@ -44,6 +44,7 @@ class ResponseFlagUtils {
   constexpr static absl::string_view DURATION_TIMEOUT = "DT";
   constexpr static absl::string_view UPSTREAM_PROTOCOL_ERROR = "UPE";
   constexpr static absl::string_view NO_CLUSTER_FOUND = "NC";
+  constexpr static absl::string_view OVERLOAD_MANAGER = "OM";
 
   static constexpr std::array ALL_RESPONSE_STRING_FLAGS{
       FlagStringAndEnum{FAILED_LOCAL_HEALTH_CHECK, ResponseFlag::FailedLocalHealthCheck},
@@ -74,6 +75,7 @@ class ResponseFlagUtils {
       FlagStringAndEnum{DURATION_TIMEOUT, ResponseFlag::DurationTimeout},
       FlagStringAndEnum{UPSTREAM_PROTOCOL_ERROR, ResponseFlag::UpstreamProtocolError},
       FlagStringAndEnum{NO_CLUSTER_FOUND, ResponseFlag::NoClusterFound},
+      FlagStringAndEnum{OVERLOAD_MANAGER, ResponseFlag::OverloadManager},
   };
 
 private:

source/extensions/access_loggers/grpc/grpc_access_log_utils.cc

@@ -37,7 +37,7 @@ void Utility::responseFlagsToAccessLogResponseFlags(
     envoy::data::accesslog::v3::AccessLogCommon& common_access_log,
     const StreamInfo::StreamInfo& stream_info) {
 
-  static_assert(StreamInfo::ResponseFlag::LastFlag == 0x1000000,
+  static_assert(StreamInfo::ResponseFlag::LastFlag == 0x2000000,
                 "A flag has been added. Fix this code.");
 
   if (stream_info.hasResponseFlag(StreamInfo::ResponseFlag::FailedLocalHealthCheck)) {
@@ -140,6 +140,10 @@ void Utility::responseFlagsToAccessLogResponseFlags(
   if (stream_info.hasResponseFlag(StreamInfo::ResponseFlag::NoClusterFound)) {
     common_access_log.mutable_response_flags()->set_no_cluster_found(true);
   }
+
+  if (stream_info.hasResponseFlag(StreamInfo::ResponseFlag::OverloadManager)) {
+    common_access_log.mutable_response_flags()->set_overload_manager(true);
+  }
 }
 
 void Utility::extractCommonAccessLogProperties(

test/common/access_log/access_log_impl_test.cc

@@ -989,6 +989,7 @@ name: accesslog
       - DT
       - UPE
       - NC
+      - OM
 typed_config:
   "@type": type.googleapis.com/envoy.extensions.access_loggers.file.v3.FileAccessLog
   path: /dev/null

test/common/http/utility_test.cc

@@ -870,6 +870,8 @@ TEST(HttpUtility, ResetReasonToString) {
             Utility::resetReasonToString(Http::StreamResetReason::RemoteRefusedStreamReset));
   EXPECT_EQ("remote error with CONNECT request",
             Utility::resetReasonToString(Http::StreamResetReason::ConnectError));
+  EXPECT_EQ("overload manager reset",
+            Utility::resetReasonToString(Http::StreamResetReason::OverloadManager));
 }
 
 class TestConfig : public Router::RouteSpecificFilterConfig {

test/extensions/access_loggers/grpc/grpc_access_log_utils_test.cc

@@ -47,6 +47,7 @@ TEST(UtilityResponseFlagsToAccessLogResponseFlagsTest, All) {
   common_access_log_expected.mutable_response_flags()->set_duration_timeout(true);
   common_access_log_expected.mutable_response_flags()->set_upstream_protocol_error(true);
   common_access_log_expected.mutable_response_flags()->set_no_cluster_found(true);
+  common_access_log_expected.mutable_response_flags()->set_overload_manager(true);
 
   EXPECT_EQ(common_access_log_expected.DebugString(), common_access_log.DebugString());
 }