WiP: Local reply mapper

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

@@ -45,6 +45,8 @@ message AccessLog {
   }
 }
 
+// [#next-major-version: In the v3 API, we should consider renaming
+// it to more generic filter]
 message AccessLogFilter {
   oneof filter_specifier {
     option (validate.required) = true;

api/envoy/config/filter/network/http_connection_manager/v2/BUILD

@@ -21,6 +21,7 @@ api_proto_library_internal(
         "//envoy/api/v2/core:config_source",
         "//envoy/api/v2/core:protocol",
         "//envoy/config/filter/accesslog/v2:accesslog",
+        "//envoy/type:format",
         "//envoy/type:percent",
     ],
 )

api/envoy/config/filter/network/http_connection_manager/v2/http_connection_manager.proto

@@ -12,6 +12,7 @@ import "envoy/api/v2/rds.proto";
 import "envoy/api/v2/srds.proto";
 import "envoy/config/filter/accesslog/v2/accesslog.proto";
 import "envoy/type/percent.proto";
+import "envoy/type/format.proto";
 
 import "google/protobuf/any.proto";
 import "google/protobuf/duration.proto";
@@ -23,7 +24,7 @@ import "validate/validate.proto";
 // [#protodoc-title: HTTP connection manager]
 // HTTP connection manager :ref:`configuration overview <config_http_conn_man>`.
 
-// [#comment:next free field: 35]
+// [#comment:next free field: 36]
 message HttpConnectionManager {
   enum CodecType {
     // For every new connection, the connection manager will determine which
@@ -456,6 +457,37 @@ message HttpConnectionManager {
   // with `prefix` match set to `/dir`. Defaults to `false`. Note that slash merging is not part of
   // `HTTP spec <https://tools.ietf.org/html/rfc3986>` and is provided for convenience.
   bool merge_slashes = 33;
+
+  // [#not-implemented-hide:]
+  // Configuration of local reply returned by Envoy. Allows to specify mappings and format of
+  // response.
+  LocalReplyConfig local_reply_config = 35;
+}
+
+message LocalReplyConfig {
+  // Configuration of list of mappers which allows to filter and change local response.
+  // Code iterate through mappers until first match of filter.
+  repeated ResponseMapper mapper = 1;
+
+  // Allows to define custom format of local reply.
+  type.StringOrJson format = 2;
+};
+
+message ResponseMapper {
+  // Filter is used to determine if the response should be changed.
+  envoy.config.filter.accesslog.v2.AccessLogFilter filter = 1
+      [(validate.rules).message.required = true];
+
+  // Rewriter defines which values in local reply should be changed.
+  ResponseRewriter rewriter = 2 [(validate.rules).message.required = true];
+}
+
+// Configuration of new value for matched local response.
+message ResponseRewriter {
+  // Status code for matched response.
+  google.protobuf.UInt32Value status_code = 1;
+
+  // TODO: add support for GRPC rewrite.
 }
 
 message Rds {

api/envoy/type/BUILD

@@ -6,6 +6,12 @@ api_proto_package(
     name = "type",
 )
 
+api_proto_library_internal(
+    name = "format",
+    srcs = ["format.proto"],
+    visibility = ["//visibility:public"],
+)
+
 api_proto_library_internal(
     name = "http_status",
     srcs = ["http_status.proto"],

api/envoy/type/format.proto

@@ -0,0 +1,20 @@
+syntax = "proto3";
+
+package envoy.type;
+
+option java_outer_classname = "FormatProto";
+option java_multiple_files = true;
+option java_package = "io.envoyproxy.envoy.type";
+
+import "google/protobuf/struct.proto";
+
+message StringOrJson {
+  // Allows to define custom format of returned data.
+  oneof format {
+    // Plain text format.
+    string string_format = 2;
+
+    // Json format as dictionary.
+    google.protobuf.Struct json_format = 3;
+  }
+}

tools/spelling_dictionary.txt

@@ -713,6 +713,7 @@ resolvers
 resync
 ret
 retriable
+rewriter
 rpcs
 rq
 rtrim