api: add filter config discovery (#11571)

Define filter config discovery. Add FDS for HTTP filters (HTTP extensions is where the pain is felt the most). Modelled after RDS with a twist of config override for re-use.

Risk Level: low (not implemented)
Testing:
Docs Changes:
Release Notes:

Issue: #7867

Signed-off-by: Kuat Yessenov <kuat@google.com>

api/envoy/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto

@@ -750,22 +750,52 @@ message ScopedRds {
       [(validate.rules).message = {required: true}];
 }
 
+// [#next-free-field: 6]
 message HttpFilter {
   option (udpa.annotations.versioning).previous_message_type =
       "envoy.config.filter.network.http_connection_manager.v2.HttpFilter";
 
+  // [#not-implemented-hide:] Configuration source specifier for the late-bound
+  // filter configuration. The HTTP Listener is warmed until all the initial
+  // filter configurations are received, unless the flag to apply the default
+  // configuration is set. Subsequent filter updates are atomic on a per-worker
+  // basis, and apply to new streams while the active streams continue using
+  // the older filter configurations. If the initial delivery of the filter
+  // configuration fails, due to a timeout for example, the optional default
+  // configuration is applied. Without a default configuration, the filter is
+  // disabled, and the HTTP listener responds with 500 immediately. After the
+  // failure, the listener continues subscribing to the subsequent filter
+  // configurations.
+  message HttpFilterConfigSource {
+    config.core.v3.ConfigSource config_source = 1;
+
+    // Optional default configuration to use as the initial configuration if
+    // there is a failure to receive the initial filter configuration or if
+    // `apply_default_config_without_warming` flag is set.
+    google.protobuf.Any default_config = 2;
+
+    // Use the default config as the initial configuration without warming and
+    // waiting for the first xDS response. Requires the default configuration
+    // to be supplied.
+    bool apply_default_config_without_warming = 3;
+  }
+
   reserved 3, 2;
 
   reserved "config";
 
-  // The name of the filter to instantiate. The name must match a
-  // :ref:`supported filter <config_http_filters>`.
+  // The name of the filter configuration. The name is used as a fallback to
+  // select an extension if the type of the configuration proto is not
+  // sufficient. It also serves as a resource name in FilterConfigDS.
   string name = 1 [(validate.rules).string = {min_bytes: 1}];
 
   // Filter specific configuration which depends on the filter being instantiated. See the supported
   // filters for further documentation.
   oneof config_type {
     google.protobuf.Any typed_config = 4;
+
+    // [#not-implemented-hide:] Configuration source specifier for FilterConfigDS.
+    HttpFilterConfigSource filter_config_ds = 5;
   }
 }
 

api/envoy/service/filter/v3/BUILD

@@ -0,0 +1,14 @@
+# DO NOT EDIT. This file is generated by tools/proto_sync.py.
+
+load("@envoy_api//bazel:api_build_system.bzl", "api_proto_package")
+
+licenses(["notice"])  # Apache 2
+
+api_proto_package(
+    has_services = True,
+    deps = [
+        "//envoy/annotations:pkg",
+        "//envoy/service/discovery/v3:pkg",
+        "@com_github_cncf_udpa//udpa/annotations:pkg",
+    ],
+)

api/envoy/service/filter/v3/filter_config_discovery.proto

@@ -0,0 +1,37 @@
+syntax = "proto3";
+
+package envoy.service.filter.v3;
+
+import "envoy/service/discovery/v3/discovery.proto";
+
+import "google/api/annotations.proto";
+
+import "envoy/annotations/resource.proto";
+import "udpa/annotations/status.proto";
+import "udpa/annotations/versioning.proto";
+
+option java_package = "io.envoyproxy.envoy.service.filter.v3";
+option java_outer_classname = "FilterConfigDiscoveryProto";
+option java_multiple_files = true;
+option java_generic_services = true;
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+
+// [#protodoc-title: FilterConfigDS]
+
+// Return filter configurations.
+service FilterConfigDiscoveryService {
+  option (envoy.annotations.resource).type = "envoy.config.core.v3.TypedExtensionConfig";
+
+  rpc StreamFilterConfigs(stream discovery.v3.DiscoveryRequest)
+      returns (stream discovery.v3.DiscoveryResponse) {
+  }
+
+  rpc DeltaFilterConfigs(stream discovery.v3.DeltaDiscoveryRequest)
+      returns (stream discovery.v3.DeltaDiscoveryResponse) {
+  }
+
+  rpc FetchFilterConfigs(discovery.v3.DiscoveryRequest) returns (discovery.v3.DiscoveryResponse) {
+    option (google.api.http).post = "/v3/discovery:filter_configs";
+    option (google.api.http).body = "*";
+  }
+}

api/versioning/BUILD

@@ -127,6 +127,7 @@ proto_library(
         "//envoy/service/discovery/v3:pkg",
         "//envoy/service/endpoint/v3:pkg",
         "//envoy/service/event_reporting/v3:pkg",
+        "//envoy/service/filter/v3:pkg",
         "//envoy/service/health/v3:pkg",
         "//envoy/service/listener/v3:pkg",
         "//envoy/service/load_stats/v3:pkg",