xds: Add a KeyValueStore-backed xDS delegate extension to contrib (#22921)

An xDS delegate extension point was added in
#22473 to enable custom behavior upon
receiving and loading xDS resources. This change creates an implementation of
the XdsResourcesDelegate interface that is backed by a KeyValueStore.

The intended use case is to enable persisting xDS resources and loading them on
startup in Envoy Mobile, in the event that the xDS control plane is unreachable.

Signed-off-by: Ali Beyad abeyad@google.com

Risk Level: Low
Testing: Unit & Integration tests
Docs Changes: N/A (hidden experimental feature)
Release Notes: N/A
Platform Specific Features: N/A

Signed-off-by: Ali Beyad <abeyad@google.com>

Mirrored from https://github.com/envoyproxy/envoy @ f28db324be3fcb6e91eb5a89d90c08617f76a2b2

contrib/envoy/extensions/config/v3alpha/BUILD

@@ -0,0 +1,12 @@
+# DO NOT EDIT. This file is generated by tools/proto_format/proto_sync.py.
+
+load("@envoy_api//bazel:api_build_system.bzl", "api_proto_package")
+
+licenses(["notice"])  # Apache 2
+
+api_proto_package(
+    deps = [
+        "//envoy/config/common/key_value/v3:pkg",
+        "@com_github_cncf_udpa//udpa/annotations:pkg",
+    ],
+)

contrib/envoy/extensions/config/v3alpha/kv_store_xds_delegate_config.proto

@@ -0,0 +1,29 @@
+syntax = "proto3";
+
+package envoy.extensions.config.v3alpha;
+
+import "envoy/config/common/key_value/v3/config.proto";
+
+import "udpa/annotations/status.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.config.v3alpha";
+option java_outer_classname = "KvStoreXdsDelegateConfigProto";
+option java_multiple_files = true;
+option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/config/v3alpha";
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+
+// [#extension: envoy.xds_delegates.kv_store]
+//
+// Configuration for a KeyValueStore-based XdsResourcesDelegate implementation. This implementation
+// updates the underlying KV store with xDS resources received from the configured management
+// servers, enabling configuration to be persisted locally and used on startup in case connectivity
+// with the xDS management servers could not be established.
+//
+// The KV Store based delegate's handling of wildcard resources (empty resource list or "*") is
+// designed for use with O(100) resources or fewer, so it's not currently advised to use this
+// feature for large configurations with heavy use of wildcard resources.
+message KeyValueStoreXdsDelegateConfig {
+  // Configuration for the KeyValueStore that holds the xDS resources.
+  // [#allow-fully-qualified-name:]
+  .envoy.config.common.key_value.v3.KeyValueStoreConfig key_value_store_config = 1;
+}

versioning/BUILD

@@ -9,6 +9,7 @@ proto_library(
     name = "active_protos",
     visibility = ["//visibility:public"],
     deps = [
+        "//contrib/envoy/extensions/config/v3alpha:pkg",
         "//contrib/envoy/extensions/filters/http/dynamo/v3:pkg",
         "//contrib/envoy/extensions/filters/http/language/v3alpha:pkg",
         "//contrib/envoy/extensions/filters/http/squash/v3:pkg",