access log: add response flag filter

api/envoy/config/filter/accesslog/v2/accesslog.proto

@@ -61,6 +61,9 @@ message AccessLogFilter {
 
     // Header filter.
     HeaderFilter header_filter = 8;
+
+    // Response flag filter.
+    ResponseFlagFilter response_flag_filter = 9;
   }
 }
 
@@ -150,3 +153,9 @@ message HeaderFilter {
   // check.
   envoy.api.v2.route.HeaderMatcher header = 1 [(validate.rules).message.required = true];
 }
+
+// Filters requests that received responses with an Envoy response flag set.
+// A list of the response flags can be found
+// in the access log formatter :ref:`documentation<config_access_log_format_response_flags>`.
+message ResponseFlagFilter {
+}

docs/root/configuration/access_log.rst

@@ -78,6 +78,8 @@ The following command operators are supported:
   TCP
     Total duration in milliseconds of the downstream connection.
 
+.. _config_access_log_format_response_flags:
+
 %RESPONSE_FLAGS%
   Additional details about the response or connection, if any. For TCP connections, the response codes mentioned in
   the descriptions do not apply. Possible values are:

docs/root/intro/version_history.rst

@@ -8,6 +8,8 @@ Version history
 * access log: added ability to format START_TIME.
 * access log: added DYNAMIC_METADATA :ref:`access log formatter <config_access_log_format>`.
 * access log: added :ref:`HeaderFilter <envoy_api_msg_config.filter.accesslog.v2.HeaderFilter>`
+  to filter logs based on request headers
+* access log: added :ref:`response flag filter <envoy_api_msg_config.filter.accesslog.v2.ResponseFlagFilter>` to filter based on the presence of Envoy response flags. 
   to filter logs based on request headers.
 * access log: gRPC Access Log Service (ALS) support added for :ref:`HTTP access logs
   <envoy_api_msg_config.accesslog.v2.HttpGrpcAccessLogConfig>`.

include/envoy/request_info/request_info.h

@@ -208,6 +208,11 @@ class RequestInfo {
    */
   virtual bool getResponseFlag(ResponseFlag response_flag) const PURE;
 
+  /**
+   * @return whether any response flag is set or not.
+   */
+  virtual bool getResponseFlag() const PURE;
+
   /**
    * @return upstream host description.
    */

source/common/access_log/access_log_impl.cc

@@ -68,6 +68,8 @@ FilterFactory::fromProto(const envoy::config::filter::accesslog::v2::AccessLogFi
     return FilterPtr{new OrFilter(config.or_filter(), runtime, random)};
   case envoy::config::filter::accesslog::v2::AccessLogFilter::kHeaderFilter:
     return FilterPtr{new HeaderFilter(config.header_filter())};
+  case envoy::config::filter::accesslog::v2::AccessLogFilter::kResponseFlagFilter:
+    return FilterPtr{new ResponseFlagFilter()};
   default:
     NOT_REACHED;
   }
@@ -174,6 +176,10 @@ bool HeaderFilter::evaluate(const RequestInfo::RequestInfo&,
   return Http::HeaderUtility::matchHeaders(request_headers, header_data_);
 }
 
+bool ResponseFlagFilter::evaluate(const RequestInfo::RequestInfo& info, const Http::HeaderMap&) {
+  return info.getResponseFlag();
+}
+
 InstanceSharedPtr
 AccessLogFactory::fromProto(const envoy::config::filter::accesslog::v2::AccessLog& config,
                             Server::Configuration::FactoryContext& context) {

source/common/access_log/access_log_impl.h

@@ -166,6 +166,18 @@ class HeaderFilter : public Filter {
   std::vector<Http::HeaderUtility::HeaderData> header_data_;
 };
 
+/**
+ * Filter requests that had a response with an Envoy response flag set.
+ */
+class ResponseFlagFilter : public Filter {
+public:
+  ResponseFlagFilter() {}
+
+  // AccessLog::Filter
+  bool evaluate(const RequestInfo::RequestInfo& info,
+                const Http::HeaderMap& request_headers) override;
+};
+
 /**
  * Access log factory that reads the configuration from proto.
  */

source/common/request_info/request_info_impl.h

@@ -123,6 +123,8 @@ struct RequestInfoImpl : public RequestInfo {
 
   bool getResponseFlag(ResponseFlag flag) const override { return response_flags_ & flag; }
 
+  bool getResponseFlag() const override { return response_flags_ != 0; }
+
   void onUpstreamHostSelected(Upstream::HostDescriptionConstSharedPtr host) override {
     upstream_host_ = host;
   }

test/common/access_log/access_log_impl_test.cc

@@ -724,6 +724,25 @@ name: envoy.file_access_log
   log->log(&request_headers_, &response_headers_, &response_trailers_, request_info_);
 }
 
+TEST_F(AccessLogImplTest, ResponseFlagFilter) {
+  const std::string yaml = R"EOF(
+name: envoy.file_access_log
+filter:
+  response_flag_filter: {}
+config:
+  path: /dev/null
+  )EOF";
+
+  InstanceSharedPtr log = AccessLogFactory::fromProto(parseAccessLogFromV2Yaml(yaml), context_);
+
+  EXPECT_CALL(*file_, write(_)).Times(0);
+  log->log(&request_headers_, &response_headers_, &response_trailers_, request_info_);
+
+  request_info_.setResponseFlag(RequestInfo::ResponseFlag::NoRouteFound);
+  EXPECT_CALL(*file_, write(_));
+  log->log(&request_headers_, &response_headers_, &response_trailers_, request_info_);
+}
+
 } // namespace
 } // namespace AccessLog
 } // namespace Envoy

test/common/access_log/test_util.h

@@ -30,6 +30,7 @@ class TestRequestInfo : public RequestInfo::RequestInfo {
   bool getResponseFlag(Envoy::RequestInfo::ResponseFlag response_flag) const override {
     return response_flags_ & response_flag;
   }
+  bool getResponseFlag() const override { return response_flags_ != 0; }
   void setResponseFlag(Envoy::RequestInfo::ResponseFlag response_flag) override {
     response_flags_ |= response_flag;
   }

test/common/request_info/request_info_impl_test.cc

@@ -96,6 +96,7 @@ TEST(RequestInfoImplTest, ResponseFlagTest) {
                                                    RateLimited};
 
   RequestInfoImpl request_info(Http::Protocol::Http2);
+  EXPECT_FALSE(request_info.getResponseFlag());
   for (ResponseFlag flag : responseFlags) {
     // Test cumulative setting of response flags.
     EXPECT_FALSE(request_info.getResponseFlag(flag))
@@ -104,6 +105,7 @@ TEST(RequestInfoImplTest, ResponseFlagTest) {
     EXPECT_TRUE(request_info.getResponseFlag(flag))
         << fmt::format("Flag: {} was expected to be set", flag);
   }
+  EXPECT_TRUE(request_info.getResponseFlag());
 }
 
 TEST(RequestInfoImplTest, MiscSettersAndGetters) {

test/mocks/request_info/mocks.h

@@ -42,6 +42,7 @@ class MockRequestInfo : public RequestInfo {
   MOCK_CONST_METHOD0(responseCode, absl::optional<uint32_t>());
   MOCK_CONST_METHOD0(bytesSent, uint64_t());
   MOCK_CONST_METHOD1(getResponseFlag, bool(ResponseFlag));
+  MOCK_CONST_METHOD0(getResponseFlag, bool());
   MOCK_CONST_METHOD0(upstreamHost, Upstream::HostDescriptionConstSharedPtr());
   MOCK_CONST_METHOD0(upstreamLocalAddress, const Network::Address::InstanceConstSharedPtr&());
   MOCK_CONST_METHOD0(healthCheck, bool());