syntax = "proto3";

package envoy.api.v2;

import "api/address.proto";
import "api/base.proto";
import "api/health_check.proto";

import "google/protobuf/wrappers.proto";

service EndpointDiscoveryService {
  // Translation of REST API to gRPC
  rpc Get(stream EndpointDiscoveryRequest)
      returns (stream EndpointDiscoveryResponse) {
  }

  // Advanced API to allow for multi-dimensional load balancing by remote
  // server. The steps are:
  // 1, The management server is configured with per cluster/zone/load metric
  //    capacity configuration. The capacity configuration definition is
  //    outside of the scope of this document.
  // 2. Envoy issues LoadBalanceRequest for a list of clusters it wants to load
  //    balance to (instead of using a basic EndpointDiscoveryRequest).
  // 3. Once a connection establishes, the management server publishes
  //    LoadBalanceResponse for all clusters requested in the first
  //    LoadBalanceRequest. This message contains per cluster/per Locality
  //    information.
  // 4. For each cluster, Envoy load balances incoming traffic to upstream hosts
  //    based on per-zone weights and/or per-instance weights (if specified)
  //    based on intra-zone LbPolicy.
  // 5. When upstream hosts reply, they optionally add header <define header
  //    name> with ASCII representation of EndpointLoadMetricStats.
  // 6. Envoy aggregates load reports over the period of time given to it in
  //    LoadBalanceResponse.load_reporting_interval. This includes aggregation
  //    stats Envoy maintains by itself (total_requests, rpc_errors etc.) as
  //    well as load metrics from upstream hosts.
  // 7. When the timer of load_reporting_interval expires, Envoy sends new
  //    LoadBalanceRequest filled with load reports for each cluster.
  // 8. The management server uses the load reports from all reported Envoys
  //    from around the world, computes global assignment and prepares traffic
  //    assignment destined for each zone Envoys are located in. Goto 3.
  // TODO(htuch): Add @amb67's diagram.
  rpc BalanceLoad(stream LoadBalanceRequest)
      returns (stream LoadBalanceResponse) {
  }
}

message EndpointDiscoveryRequest {
  repeated string cluster_name = 1;
  Node node = 2;
}

message LbEndpoint {
  Endpoint endpoint = 1;

  // Optional health status when known and supplied by EDS server.
  HealthStatus health_status = 2;

  // The optional canary status of the upstream host. Envoy uses the canary
  // status for various statistics and load balancing tasks documented
  // elsewhere.
  google.protobuf.BoolValue canary = 3;
  // The optional load balancing weight of the upstream host, in the range 1 -
  // 100. Envoy uses the load balancing weight in some of the built in load
  // balancers. All load balancing weights in a locality must sum to 100%.
  // The effective load balancing weight is load_balancing_weight multiplied by
  // the locality wide load_balancing_weight. If unspecified, each host is
  // presumed to have equal weight in a locality.
  // TODO(htuch): [V2-API-DIFF] Do we want all weights to sum to 100%, or to
  // instead use the sum of all weights in the denominator when computing
  // effective the weight ratio as done in v1?
  google.protobuf.UInt32Value load_balancing_weight = 4;
}

// All endpoints belonging to a Locality.
message LocalityEndpoints {
  Locality locality = 1;
  repeated LbEndpoint lb_endpoints = 2;

  // Optional: Per region/zone/sub_zone weight - range 1-100. All load balancing
  // weights in a cluster must sum to 100%. If unspecified, each locality is
  // presumed to have equal weight in a cluster.
  // TODO(htuch): [V2-API-DIFF] Do we want all weights to sum to 100%, or to
  // instead use the sum of all weights in the denominator when computing
  // effective the weight ratio as done in v1?
  google.protobuf.UInt32Value load_balancing_weight = 3;
}

message EndpointDiscoveryResponse {
  repeated ClusterLoadBalance cluster_endpoints = 1;
}

// Example load report from a single request:
//
// [metric name, metric value]
// * cpu_seconds, 0.7
// * flash_utilization, 75
//
// When aggregating Envoy needs to count how many request's load reports
// included each metric type, so Envoy can account for requests that don't
// include that metric type. e.g.:
//
// [name, count, sum of values]
// * cpu_seconds, 10, 17.5
// * flash_utilization, 5, 375
message EndpointLoadMetricStats {
  // Name of the metric; may be empty.
  string metric_name = 1;
  // Number of calls that finished and included this metric.
  uint64 num_requests_finished_with_metric = 2;
  // Sum of metric values across all calls that finished with this metric for
  // load_reporting_interval.
  double total_metric_value = 3;
}

// These are stats Envoy reports to GLB every so often. Report frequency is
// defined by LoadBalanceResponse.interval
// Stats per upstream region/zone and optionally per subzone
message UpstreamLocalityStats {
  // Name of zone, region and optionally endpoint group this metrics was
  // collected from. Zone and region names could be empty if unknown.
  string Locality = 1;

  // The total number of requests sent by this Envoy since the last report.
  uint64 total_requests = 2;
  // The total number of unfinished requests
  uint64 total_requests_in_progress = 3;
  // The number of errors since the last report.
  enum TcpErrorType {
    TIMEOUT = 0;
    // TODO(htuch): Fill in additional TcpErrorType values.
  }
  // TODO(htuch): Ideally we would have the tcp_errors key be TcpErrorType, but
  // enums are not supported as map key types. Maybe make this a repeated
  // message with TcpErrorType x uint64 pairs.
  map<uint32, uint64> tcp_errors = 4;
  // HTTP status code, count
  map<uint32, uint64> http_errors = 5;
  // GRCP status code, count
  map<uint32, uint64> grpc_errors = 6;
  // The number of dropped requests since the last report.
  uint64 dropped_requests = 7;

  // Stats for multi-dimensional load balancing.
  repeated EndpointLoadMetricStats load_metric_stats = 8;
}

// Per cluster stats
message ClusterStats {
  string cluster_name = 1;
  // Need at least one.
  repeated UpstreamLocalityStats upstream_locality_stats = 2;
}

message LoadBalanceRequest {
  Node node = 1;  // zone/region where this Envoy runs
  repeated ClusterStats cluster_stats = 3;
}

// Each route from RDS will map to a single cluster or traffic split across
// clusters using weights expressed in the RDS WeightedCluster.
//
// With EDS, each cluster is treated independently from a LB perspective, with
// LB taking place between the Localities within a cluster and at a finer
// granularity between the hosts within a locality. For a given cluster, the
// effective weight of a host is its load_balancing_weight multiplied by the
// load_balancing_weight of its Locality.
message ClusterLoadBalance {
  string cluster_name = 1;
  repeated LocalityEndpoints endpoints = 2;
  // In the case where all endpoints for a particular zone/subzone are
  // unavailable/unhealthy, additional endpoints are given out for use in case
  // of catastrophic failure. They also have weights.
  repeated LocalityEndpoints failover_endpoints = 3;
  message Policy {
    // Percentage of traffic (0-100) that should be dropped. This
    // action allows protection of upstream hosts should they unable to
    // recover from an outage or should they be unable to autoscale and hence
    // overall incoming traffic volume need to be trimmed to protect them.
    // [V2-API-DIFF] This is known as maintenance mode in v1.
    double drop_overload = 1;
  }
  Policy policy = 4;
}

message LoadBalanceResponse {
  repeated ClusterLoadBalance clusters = 1;
  // The default is 10 seconds.
  Duration load_reporting_interval = 2;
}