// This is heavily derived from
// https://lyft.github.io/envoy/docs/configuration/http_conn_man/route_config/route_config.html#config-http-conn-man-route-table.
// The v2 gRPC API differences are tagged with [V2-API-DIFF].

syntax = "proto3";

package envoy.api.v2;

import "api/base.proto";

import "google/protobuf/struct.proto";
import "google/protobuf/wrappers.proto";

service RouteDiscoveryService {
  rpc StreamRoutes(RouteDiscoveryRequest)
      returns (stream RouteDiscoveryResponse) {
  }
}

message RouteDiscoveryRequest {
  Node node = 1;
  // The name of the route configuration. This allows an Envoy configuration
  // with multiple HTTP listeners (and associated HTTP connection manager
  // filters) to use different route configurations. Each listener will bind its
  // HTTP connection manager filter to a route table via this identifier.
  string route_config_name = 2;
}

message RouteDiscoveryResponse {
  RouteConfiguration route_table = 1;
}

// Envoy supports priority routing both at the route and the virtual cluster
// level. The current priority implementation uses different connection pool
// and circuit breaking settings for each priority level. This means that even
// for HTTP/2 requests, two physical connections will be used to an upstream
// host. In the future Envoy will likely support true HTTP/2 priority over a
// single connection.
enum RoutingPriority {
  DEFAULT = 0;
  HIGH = 1;
}

// Compared to the cluster field that specifies a single upstream cluster as the
// target of a request, the weighted_clusters option allows for specification of
// multiple upstream clusters along with weights that indicate the percentage of
// traffic to be forwarded to each cluster. The router selects an upstream
// cluster based on the weights.
message WeightedCluster {
  message ClusterWeight {
    // Name of the upstream cluster. The cluster must exist in the cluster
    // manager configuration.
    string name = 1;
    // An integer between 0-100. When a request matches the route, the choice of
    // an upstream cluster is determined by its weight. The sum of weights
    // across all entries in the clusters array must add up to 100.
    google.protobuf.UInt32Value weight = 2;
  }
  // Specifies one or more upstream clusters associated with the route.
  repeated ClusterWeight clusters = 1;
  // Specifies the runtime key prefix that should be used to construct the
  // runtime keys associated with each cluster. When the runtime_key_prefix is
  // specified, the router will look for weights associated with each upstream
  // cluster under the key runtime_key_prefix + "." + cluster[i].name where
  // cluster[i] denotes an entry in the clusters array field. If the runtime
  // key for the cluster does not exist, the value specified in the
  // configuration file will be used as the default weight. See the runtime
  // documentation for how key names map to the underlying implementation.
  string runtime_key_prefix = 2;
}

message RouteMatch {
  oneof path_specifier {
    // If specified, the route is a prefix rule meaning that the prefix must
    // match the beginning of the :path header. Either prefix or path must be
    // specified.
    string prefix = 1;
    // If specified, the route is an exact path rule meaning that the path must
    // exactly match the :path header once the query string is removed. Either
    // prefix or path must be specified.
    string path = 2;
  }
  // Indicates that prefix/path matching should be case insensitive. The default
  // is true.
  google.protobuf.BoolValue case_sensitive = 3;

  // A runtime route configuration can be used to roll out route changes in a
  // gradual manner without full code/config deploys. Refer to traffic shifting
  // docs for additional documentation.
  message Runtime {
    // Specifies the runtime key name that should be consulted to determine
    // whether the route matches or not. See the runtime documentation for how
    // key names map to the underlying implementation.
    string key = 1;
    // An integer between 0-100. Every time the route is considered for a match,
    // a random number between 0-99 is selected. If the number is <= the value
    // found in the key (checked first) or, if the key is not present, the
    // default value, the route is a match (assuming everything also about the
    // route matches).
    google.protobuf.UInt32Value default_value = 2;
  }
  // Indicates that the route should additionally match on a runtime key.
  Runtime runtime = 4;

  // Specifies a set of headers that the route should match on. The router will
  // check the request’s headers against all the specified headers in the route
  // config. A match will happen if all the headers in the route are present in
  // the request with the same values (or based on presence if the value field
  // is not in the config).
  repeated HeaderMatcher headers = 5;
}

message ForwardAction {
  oneof cluster_specifier {
    // Indicates the upstream cluster to which the request should be forwarded
    // to.
    string cluster = 1;
    // Envoy will determine the cluster to route to by reading the value of the
    // HTTP header named by cluster_header from the request headers. If the
    // header is not found or the referenced cluster does not exist, Envoy will
    // return a 404 response.
    string cluster_header = 2;
    // Multiple upstream clusters can be specified for a given route. The
    // request is forwarded to one of the upstream clusters based on weights
    // assigned to each cluster. See traffic splitting for additional
    // documentation.
    WeightedCluster weighted_clusters = 3;
  }

  // Indicates that during forwarding, the matched prefix (or path) should be
  // swapped with this value. This option allows application URLs to be rooted
  // at a different path from those exposed at the reverse proxy layer.
  string prefix_rewrite = 4;
  oneof host_rewrite_specifier {
    // Indicates that during forwarding, the host header will be swapped with
    // this value.
    string host_rewrite = 5;
    // Indicates that during forwarding, the host header will be swapped with
    // the hostname of the upstream host chosen by the cluster manager. This
    // option is applicable only when the destination cluster for a route is of
    // type strict_dns or logical_dns. Setting this to true with other cluster
    // types has no effect.
    google.protobuf.BoolValue auto_host_rewrite = 6;
  }

  // Specifies the timeout for the route. If not specified, the default is 15s.
  // Note that this timeout includes all retries. See also
  // x-envoy-upstream-rq-timeout-ms, x-envoy-upstream-rq-per-try-timeout-ms, and
  // the retry overview.
  google.protobuf.UInt32Value timeout_ms = 7;

  message RetryPolicy {
    // Specifies the conditions under which retry takes place. These are the
    // same conditions documented for x-envoy-retry-on.
    string retry_on = 1;
    // Specifies the allowed number of retries. This parameter is optional and
    // defaults to 1. These are the same conditions documented for
    // x-envoy-max-retries.
    google.protobuf.UInt32Value num_retries = 2;
    // Specifies a non-zero timeout per retry attempt. This parameter is
    // optional. The same conditions documented for
    // x-envoy-upstream-rq-per-try-timeout-ms apply.
    google.protobuf.UInt32Value per_try_timeout_ms = 3;
  }
  // Indicates that the route has a retry policy.
  RetryPolicy retry_policy = 8;

  // Indicates that the route has a shadow policy.
  message ShadowPolicy {
    // Specifies the cluster that requests will be shadowed to. The cluster must
    // exist in the cluster manager configuration.
    string cluster = 1;
    // If not specified, all requests to the target cluster will be shadowed. If
    // specified, Envoy will lookup the runtime key to get the % of requests to
    // shadow. Valid values are from 0 to 10000, allowing for increments of
    // 0.01% of requests to be shadowed. If the runtime key is specified in the
    // configuration but not present in runtime, 0 is the default and thus 0% of
    // requests will be shadowed.
    string runtime_key = 2;
  }
  ShadowPolicy shadow_policy = 9;

  RoutingPriority priority = 10;

  // Specifies a set of headers that will be added to requests matching this
  // route.
  repeated HeaderValue request_headers_to_add = 11;

  // Specifies a set of optional route configuration values that can be accessed
  // by filters.
  google.protobuf.Struct opaque_config = 12;

  // Specifies a set of rate limit configurations that could be applied to the
  // route.
  repeated RateLimit rate_limits = 13;

  // Specifies if the rate limit filter should include the virtual host rate
  // limits. By default, if the route configured rate limits, the virtual host
  // rate_limits are not applied to the request.
  google.protobuf.BoolValue include_vh_rate_limits = 14;

  message HashPolicy {
    string header_name = 1;
    // Do we want to extend this for additional session affinity inputs?
    // [V2-API-DIFF]
  }
  repeated HashPolicy hash_policy = 15;
}

message RedirectAction {
  // A 302 redirect response will be sent which swaps the host portion of the
  // URL with this value.
  string host_redirect = 1;
  // A 302 redirect response will be sent which swaps the path portion of the
  // URL with this value.
  string path_redirect = 2;
}

// The match/action distinction in Route is surfaced explicitly in the v2 API
// [V2-API-DIFF].
message Route {
  RouteMatch match = 1;
  oneof action {
    // Forward to some upstream cluster.
    ForwardAction forward = 2;
    // Return a 302 redirect.
    RedirectAction redirect = 3;
  }
}

// A virtual cluster is a way of specifying a regex matching rule against
// certain important endpoints such that statistics are generated explicitly for
// the matched requests. The reason this is useful is that when doing
// prefix/path matching Envoy does not always know what the application
// considers to be an endpoint. Thus, it’s impossible for Envoy to generically
// emit per endpoint statistics. However, often systems have highly critical
// endpoints that they wish to get “perfect” statistics on. Virtual cluster
// statistics are perfect in the sense that they are emitted on the downstream
// side such that they include network level failures.
message VirtualCluster {
  // Specifies a regex pattern to use for matching requests.
  string pattern = 1;

  // Specifies the name of the virtual cluster. The virtual cluster name as well
  // as the virtual host name are used when emitting statistics.
  string name = 2;

  // Optionally specifies the HTTP method to match on. For example GET, PUT,
  // etc.
  string method = 3;

  // Optionally specifies the virtual cluster routing priority.
  // [V2-API-DIFF] Virtual clusters are promoted mostly as a logical grouping
  // for the purposes of stats. This is an exception, where the forwarding
  // action is modified by the virtual cluster. It would be good to understand
  // if we want to do more or less in the way of overriding route forwarding
  // actions via virtual clusters in the v2 API.
  RoutingPriority priority = 4;
}

// See
// https://lyft.github.io/envoy/docs/configuration/http_conn_man/route_config/rate_limits.html
message RateLimit {
  // Refers to the stage set in the filter. The rate limit configuration only
  // applies to filters with the same stage number. The default stage number is
  // 0.
  // NOTE: The filter supports a range of 0 - 10 inclusively for stage numbers.
  google.protobuf.UInt32Value stage = 1;

  // The key to be set in runtime to disable this rate limit configuration.
  string disable_key = 2;

  message RateLimitAction {
    enum ActionType {
      SOURCE_CLUSTER = 0;
      DESTINATION_CLUSTER = 1;
      REQUEST_HEADERS = 2;
      REMOTE_ADDRESS = 3;
      GENERIC_KEY = 4;
      HEADER_VALUE_MATCH = 5;
    }
    ActionType type = 1;

    message RequestHeaders {
      // The header name to be queried from the request headers. The header’s
      // value is used to populate the value of the descriptor entry for the
      // descriptor_key.
      string header_name = 1;
      // The key to use in the descriptor entry.
      string descriptor_key = 2;
    }

    message HeaderValueMatch {
      // The value to use in the descriptor entry.
      string descriptor_value = 1;
      // If set to true, the action will append a descriptor entry when the
      // request matches the headers. If set to false, the action will append a
      // descriptor entry when the request does not match the headers. The
      // default value is true.
      google.protobuf.BoolValue expect_match = 2;
      // Specifies a set of headers that the rate limit action should match
      // on. The action will check the request’s headers against all the
      // specified headers in the config. A match will happen if all the
      // headers in the config are present in the request with the same values
      // (or based on presence if the value field is not in the config).
      repeated HeaderMatcher headers = 3;
    }

    oneof action_details {
      RequestHeaders request_headers = 2;
      string generic_key = 3;
      HeaderValueMatch header_value_match = 4;
    }
  }
  // A list of actions that are to be applied for this rate limit configuration.
  // Order matters as the actions are processed sequentially and the descriptor
  // is composed by appending descriptor entries in that sequence. If an action
  // cannot append a descriptor entry, no descriptor is generated for the
  // configuration. See composing actions for additional documentation.
  repeated RateLimitAction actions = 3;
}

// Header name/value pair.
message HeaderValue {
  // Header name.
  string key = 1;
  // Header value.
  string value = 2;
}

message HeaderMatcher {
  // Specifies the name of the header in the request.
  string name = 1;
  // Specifies the value of the header. If the value is absent a request that
  // has the name header will match, regardless of the header’s value.
  string value = 2;
  // Specifies whether the header value is a regular expression or not.
  // Defaults to false.
  google.protobuf.BoolValue regex = 3;
}

message VirtualHost {
  // The logical name of the virtual host. This is used when emitting certain
  // statistics but is not relevant for forwarding.
  string name = 1;

  // A list of domains (host/authority header) that will be matched to this
  // virtual host. Wildcard hosts are supported in the form of “*.foo.com” or
  // “*-bar.foo.com”. Note that the wildcard will not match the empty string.
  // e.g. “*-bar.foo.com” will match “baz-bar.foo.com” but not “-bar.foo.com”.
  // Additionally, a special entry “*” is allowed which will match any
  // host/authority header. Only a single virtual host in the entire route
  // configuration can match on “*”. A domain must be unique across all virtual
  // hosts or the config will fail to load.
  repeated string domains = 2;

  // The list of routes that will be matched, in order, for incoming requests.
  // The first route that matches will be used.
  repeated Route routes = 3;

  enum TlsRequirementType {
    // No TLS requirement for the virtual host.
    NONE = 0;
    // External requests must use TLS. If a request is external and it is not
    // using TLS, a 302 redirect will be sent telling the client to use HTTPS.
    EXTERNAL_ONLY = 1;
    // All requests must use TLS. If a request is not using TLS, a 302 redirect
    // will be sent telling the client to use HTTPS.
    ALL = 2;
  }
  // Specifies the type of TLS enforcement the virtual host expects.
  TlsRequirementType require_tls = 4;

  // A list of virtual clusters defined for this virtual host. Virtual clusters
  // are used for additional statistics gathering.
  repeated VirtualCluster virtual_clusters = 5;

  // Specifies a set of rate limit configurations that will be applied to the
  // virtual host.
  repeated RateLimit rate_limits = 6;

  // Specifies a list of HTTP headers that should be added to each request
  // handled by this virtual host. In the presence of duplicate header keys,
  // precedence rules apply.
  repeated HeaderValue request_headers_to_add = 7;
}

message RouteConfiguration {
  // An array of virtual hosts that make up the route table.
  repeated VirtualHost virtual_hosts = 1;

  // Specifies a list of HTTP headers that the connection manager will consider
  // to be internal only. If they are found on external requests they will be
  // cleaned prior to filter invocation. See x-envoy-internal for more
  // information.
  repeated string internal_only_headers = 2;

  // Specifies a list of HTTP headers that should be added to each response that
  // the connection manager encodes.
  repeated HeaderValue response_headers_to_add = 3;

  // Specifies a list of HTTP headers that should be removed from each response
  // that the connection manager encodes.
  repeated string response_headers_to_remove = 4;

  // Specifies a list of HTTP headers that should be added to each request
  // forwarded by the HTTP connection manager. In the presence of duplicate
  // header keys, precendence rules apply.
  repeated HeaderValue request_headers_to_add = 5;
}