[Overload] Active downstream connections resource monitor (#23361)

* [Overload] Active downstream connections resource monitor

Signed-off-by: Kateryna Nezdolii <nezdolik@spotify.com>

Mirrored from https://github.com/envoyproxy/envoy @ c5199512e9d3d0c393dfdfbb815f5796b1c3940b

BUILD

@@ -257,6 +257,7 @@ proto_library(
         "//envoy/extensions/rbac/matchers/upstream_ip_port/v3:pkg",
         "//envoy/extensions/regex_engines/v3:pkg",
         "//envoy/extensions/request_id/uuid/v3:pkg",
+        "//envoy/extensions/resource_monitors/downstream_connections/v3:pkg",
         "//envoy/extensions/resource_monitors/fixed_heap/v3:pkg",
         "//envoy/extensions/resource_monitors/injected_resource/v3:pkg",
         "//envoy/extensions/retry/host/omit_canary_hosts/v3:pkg",

envoy/extensions/resource_monitors/downstream_connections/v3/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 = [
+        "@com_github_cncf_udpa//udpa/annotations:pkg",
+        "@com_github_cncf_udpa//xds/annotations/v3:pkg",
+    ],
+)

envoy/extensions/resource_monitors/downstream_connections/v3/downstream_connections.proto

@@ -0,0 +1,25 @@
+syntax = "proto3";
+
+package envoy.extensions.resource_monitors.downstream_connections.v3;
+
+import "xds/annotations/v3/status.proto";
+
+import "udpa/annotations/status.proto";
+import "validate/validate.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.resource_monitors.downstream_connections.v3";
+option java_outer_classname = "DownstreamConnectionsProto";
+option java_multiple_files = true;
+option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/resource_monitors/downstream_connections/v3;downstream_connectionsv3";
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+option (xds.annotations.v3.file_status).work_in_progress = true;
+
+// [#protodoc-title: Downstream connections]
+// [#extension: envoy.resource_monitors.downstream_connections]
+
+// The downstream connections resource monitor tracks the global number of open downstream connections.
+message DownstreamConnectionsConfig {
+  // Maximum threshold for global open downstream connections, defaults to 0.
+  // If monitor is enabled in Overload manager api, this field should be explicitly configured with value greater than 0.
+  int64 max_active_downstream_connections = 1 [(validate.rules).int64 = {gt: 0}];
+}

versioning/BUILD

@@ -202,6 +202,7 @@ proto_library(
         "//envoy/extensions/rbac/matchers/upstream_ip_port/v3:pkg",
         "//envoy/extensions/regex_engines/v3:pkg",
         "//envoy/extensions/request_id/uuid/v3:pkg",
+        "//envoy/extensions/resource_monitors/downstream_connections/v3:pkg",
         "//envoy/extensions/resource_monitors/fixed_heap/v3:pkg",
         "//envoy/extensions/resource_monitors/injected_resource/v3:pkg",
         "//envoy/extensions/retry/host/omit_canary_hosts/v3:pkg",