syntax = "proto3";

package envoy.api.v2;

import "api/base.proto";

import "google/protobuf/any.proto";

// [#protodoc-title: Common discovery API components]

// See https://github.com/lyft/envoy-api#apis for a description of the role of
// ADS and how it is intended to be used by a management server. ADS requests
// have the same structure as their singleton xDS counterparts, but can
// multiplex many resource types on a single stream. The type_url in the
// DiscoveryRequest/DiscoveryResponse provides sufficient information to recover
// the multiplexed singleton APIs at the Envoy instance and management server.
service AggregatedDiscoveryService {
  // This is a gRPC-only API.
  rpc StreamAggregatedResources(stream DiscoveryRequest)
      returns (stream DiscoveryResponse) {
  }
}

// A DiscoveryRequest requests a set of versioned resources of the same type for
// a given Envoy node on some API.
message DiscoveryRequest {
  // The version_info provided in the request messages will be the version_info
  // received with the most recent successfully processed response or empty on
  // the first request. It is expected that no new request is sent after a
  // response is received until the Envoy instance is ready to ACK/NACK the new
  // configuration. ACK/NACK takes place by returning the new API config version
  // as applied or the previous API config version respectively. Each type_url
  // (see below) has an independent version associated with it.
  string version_info = 1;
  Node node = 2;
  // List of resources to subscribe to, e.g. list of cluster names or a route
  // configuration name. If this is empty, all resources for the API are
  // returned. LDS/CDS expect empty resource_names, since this is global
  // discovery for the Envoy instance. The LDS and CDS responses will then imply
  // a number of resources that need to be fetched via EDS/RDS, which will be
  // explicitly enumerated in resource_names.
  repeated string resource_names = 3;
  // Type of the resource that is being requested, e.g.
  // "type.googleapis.com/envoy.api.v2.ClusterLoadAssignment". This is implicit
  // in requests made via singleton xDS APIs such as CDS, LDS, etc. but is
  // required for ADS.
  string type_url = 4;
  // nonce corresponding to DiscoveryResponse being ACK/NACKed. See above
  // discussion on version_info and the DiscoveryResponse nonce comment. This
  // may be empty if no nonce is available, e.g. at startup or for non-stream
  // xDS implementations.
  string response_nonce = 5;
}

message DiscoveryResponse {
  string version_info = 1;
  repeated google.protobuf.Any resources = 2;
  // Canary is used to support two Envoy command line flags:
  //
  // * --terminate-on-canary-transition-failure. When set, Envoy is able to
  //   terminate if it detects that configuration is stuck at canary. Consider
  //   this example sequence of updates:
  //   - Management server applies a canary config successfully.
  //   - Management server rolls back to a production config.
  //   - Envoy rejects the new production config.
  //   Since there is no sensible way to continue receiving configuration
  //   updates, Envoy will then terminate and apply production config from a
  //   clean slate.
  // * --dry-run-canary. When set, a canary response will never be applied, only
  //   validated via a dry run.
  bool canary = 3;
  // Type URL for resources. This must be consistent with the type_url in the
  // Any messages for resources if resources is non-empty. This effectively
  // identifies the xDS API when muxing over ADS.
  string type_url = 4;
  // For gRPC based subscriptions, the nonce provides a way to explicitly ack a
  // specific DiscoveryResponse in a following DiscoveryRequest. Additional
  // messages may have been sent by Envoy to the management server for the
  // previous version on the stream prior to this DiscoveryResponse, that were
  // unprocessed at response send time. The nonce allows the management server
  // to ignore any further DiscoveryRequests for the previous version until a
  // DiscoveryRequest bearing the nonce. The nonce is optional and is not
  // required for non-stream based xDS implementations.
  string nonce = 5;
}