.. _config_overview_v2: Overview ======== The Envoy v2 APIs are defined as `proto3 `_ `Protocol Buffers `_ in the :repo:`api tree `. They support: * Streaming delivery of :ref:`xDS ` API updates via gRPC. This reduces resource requirements and can lower the update latency. * A new REST-JSON API in which the JSON/YAML formats are derived mechanically via the `proto3 canonical JSON mapping `_. * Delivery of updates via the filesystem, REST-JSON or gRPC endpoints. * Advanced load balancing through an extended endpoint assignment API and load and resource utilization reporting to management servers. * :ref:`Stronger consistency and ordering properties ` when needed. The v2 APIs still maintain a baseline eventual consistency model. See the :ref:`xDS protocol description ` for further details on aspects of v2 message exchange between Envoy and the management server. .. _config_overview_v2_bootstrap: Bootstrap configuration ----------------------- To use the v2 API, it's necessary to supply a bootstrap configuration file. This provides static server configuration and configures Envoy to access :ref:`dynamic configuration if needed `. This is supplied on the command-line via the :option:`-c` flag, i.e.: .. code-block:: console ./envoy -c .{json,yaml,pb,pb_text} where the extension reflects the underlying v2 config representation. The :ref:`Bootstrap ` message is the root of the configuration. A key concept in the :ref:`Bootstrap ` message is the distinction between static and dynamic resources. Resources such as a :ref:`Listener ` or :ref:`Cluster ` may be supplied either statically in :ref:`static_resources ` or have an xDS service such as :ref:`LDS ` or :ref:`CDS ` configured in :ref:`dynamic_resources `. Example ------- Below we will use YAML representation of the config protos and a running example of a service proxying HTTP from 127.0.0.1:10000 to 127.0.0.2:1234. Static ^^^^^^ A minimal fully static bootstrap config is provided below: .. code-block:: yaml admin: access_log_path: /tmp/admin_access.log address: socket_address: { address: 127.0.0.1, port_value: 9901 } static_resources: listeners: - name: listener_0 address: socket_address: { address: 127.0.0.1, port_value: 10000 } filter_chains: - filters: - name: envoy.http_connection_manager typed_config: "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager stat_prefix: ingress_http codec_type: AUTO route_config: name: local_route virtual_hosts: - name: local_service domains: ["*"] routes: - match: { prefix: "/" } route: { cluster: some_service } http_filters: - name: envoy.router clusters: - name: some_service connect_timeout: 0.25s type: STATIC lb_policy: ROUND_ROBIN load_assignment: cluster_name: some_service endpoints: - lb_endpoints: - endpoint: address: socket_address: address: 127.0.0.1 port_value: 1234 Mostly static with dynamic EDS ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A bootstrap config that continues from the above example with :ref:`dynamic endpoint discovery ` via an :ref:`EDS` gRPC management server listening on 127.0.0.1:5678 is provided below: .. code-block:: yaml admin: access_log_path: /tmp/admin_access.log address: socket_address: { address: 127.0.0.1, port_value: 9901 } static_resources: listeners: - name: listener_0 address: socket_address: { address: 127.0.0.1, port_value: 10000 } filter_chains: - filters: - name: envoy.http_connection_manager typed_config: "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager stat_prefix: ingress_http codec_type: AUTO route_config: name: local_route virtual_hosts: - name: local_service domains: ["*"] routes: - match: { prefix: "/" } route: { cluster: some_service } http_filters: - name: envoy.router clusters: - name: some_service connect_timeout: 0.25s lb_policy: ROUND_ROBIN type: EDS eds_cluster_config: eds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: xds_cluster - name: xds_cluster connect_timeout: 0.25s type: STATIC lb_policy: ROUND_ROBIN http2_protocol_options: {} upstream_connection_options: # configure a TCP keep-alive to detect and reconnect to the admin # server in the event of a TCP socket half open connection tcp_keepalive: {} load_assignment: cluster_name: xds_cluster endpoints: - lb_endpoints: - endpoint: address: socket_address: address: 127.0.0.1 port_value: 5678 Notice above that *xds_cluster* is defined to point Envoy at the management server. Even in an otherwise completely dynamic configurations, some static resources need to be defined to point Envoy at its xDS management server(s). It's important to set appropriate :ref:`TCP Keep-Alive options ` in the `tcp_keepalive` block. This will help detect TCP half open connections to the xDS management server and re-establish a full connection. In the above example, the EDS management server could then return a proto encoding of a :ref:`DiscoveryResponse `: .. code-block:: yaml version_info: "0" resources: - "@type": type.googleapis.com/envoy.api.v2.ClusterLoadAssignment cluster_name: some_service endpoints: - lb_endpoints: - endpoint: address: socket_address: address: 127.0.0.2 port_value: 1234 The versioning and type URL scheme that appear above are explained in more detail in the :ref:`streaming gRPC subscription protocol ` documentation. Dynamic ^^^^^^^ A fully dynamic bootstrap configuration, in which all resources other than those belonging to the management server are discovered via xDS is provided below: .. code-block:: yaml admin: access_log_path: /tmp/admin_access.log address: socket_address: { address: 127.0.0.1, port_value: 9901 } dynamic_resources: lds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: xds_cluster cds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: xds_cluster static_resources: clusters: - name: xds_cluster connect_timeout: 0.25s type: STATIC lb_policy: ROUND_ROBIN http2_protocol_options: {} upstream_connection_options: # configure a TCP keep-alive to detect and reconnect to the admin # server in the event of a TCP socket half open connection tcp_keepalive: {} load_assignment: cluster_name: xds_cluster endpoints: - lb_endpoints: - endpoint: address: socket_address: address: 127.0.0.1 port_value: 5678 The management server could respond to LDS requests with: .. code-block:: yaml version_info: "0" resources: - "@type": type.googleapis.com/envoy.api.v2.Listener name: listener_0 address: socket_address: address: 127.0.0.1 port_value: 10000 filter_chains: - filters: - name: envoy.http_connection_manager typed_config: "@type": type.googleapis.com/envoy.config.filter.network.http_connection_manager.v2.HttpConnectionManager stat_prefix: ingress_http codec_type: AUTO rds: route_config_name: local_route config_source: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: xds_cluster http_filters: - name: envoy.router The management server could respond to RDS requests with: .. code-block:: yaml version_info: "0" resources: - "@type": type.googleapis.com/envoy.api.v2.RouteConfiguration name: local_route virtual_hosts: - name: local_service domains: ["*"] routes: - match: { prefix: "/" } route: { cluster: some_service } The management server could respond to CDS requests with: .. code-block:: yaml version_info: "0" resources: - "@type": type.googleapis.com/envoy.api.v2.Cluster name: some_service connect_timeout: 0.25s lb_policy: ROUND_ROBIN type: EDS eds_cluster_config: eds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: xds_cluster The management server could respond to EDS requests with: .. code-block:: yaml version_info: "0" resources: - "@type": type.googleapis.com/envoy.api.v2.ClusterLoadAssignment cluster_name: some_service endpoints: - lb_endpoints: - endpoint: address: socket_address: address: 127.0.0.2 port_value: 1234 .. _config_overview_v2_management_server: xDS API endpoints ----------------- A v2 xDS management server will implement the below endpoints as required for gRPC and/or REST serving. In both streaming gRPC and REST-JSON cases, a :ref:`DiscoveryRequest ` is sent and a :ref:`DiscoveryResponse ` received following the :ref:`xDS protocol `. .. _v2_grpc_streaming_endpoints: gRPC streaming endpoints ^^^^^^^^^^^^^^^^^^^^^^^^ .. http:post:: /envoy.api.v2.ClusterDiscoveryService/StreamClusters See :repo:`cds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml cds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set in the :ref:`dynamic_resources ` of the :ref:`Bootstrap ` config. .. http:post:: /envoy.api.v2.EndpointDiscoveryService/StreamEndpoints See :repo:`eds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml eds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set in the :ref:`eds_cluster_config ` field of the :ref:`Cluster ` config. .. http:post:: /envoy.api.v2.ListenerDiscoveryService/StreamListeners See :repo:`lds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml lds_config: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set in the :ref:`dynamic_resources ` of the :ref:`Bootstrap ` config. .. http:post:: /envoy.api.v2.RouteDiscoveryService/StreamRoutes See :repo:`rds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml route_config_name: some_route_name config_source: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set in the :ref:`rds ` field of the :ref:`HttpConnectionManager ` config. .. http:post:: /envoy.api.v2.ScopedRoutesDiscoveryService/StreamScopedRoutes See :repo:`srds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml name: some_scoped_route_name scoped_rds: config_source: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set in the :ref:`scoped_routes ` field of the :ref:`HttpConnectionManager ` config. .. http:post:: /envoy.service.discovery.v2.SecretDiscoveryService/StreamSecrets See :repo:`sds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml name: some_secret_name config_source: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set inside a :ref:`SdsSecretConfig ` message. This message is used in various places such as the :ref:`CommonTlsContext `. .. http:post:: /envoy.service.discovery.v2.RuntimeDiscoveryService/StreamRuntime See :repo:`rtds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml name: some_runtime_layer_name config_source: api_config_source: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_xds_cluster is set inside the :ref:`rtds_layer ` field. REST endpoints ^^^^^^^^^^^^^^ .. http:post:: /v2/discovery:clusters See :repo:`cds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml cds_config: api_config_source: api_type: REST cluster_names: [some_xds_cluster] is set in the :ref:`dynamic_resources ` of the :ref:`Bootstrap ` config. .. http:post:: /v2/discovery:endpoints See :repo:`eds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml eds_config: api_config_source: api_type: REST cluster_names: [some_xds_cluster] is set in the :ref:`eds_cluster_config ` field of the :ref:`Cluster ` config. .. http:post:: /v2/discovery:listeners See :repo:`lds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml lds_config: api_config_source: api_type: REST cluster_names: [some_xds_cluster] is set in the :ref:`dynamic_resources ` of the :ref:`Bootstrap ` config. .. http:post:: /v2/discovery:routes See :repo:`rds.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml route_config_name: some_route_name config_source: api_config_source: api_type: REST cluster_names: [some_xds_cluster] is set in the :ref:`rds ` field of the :ref:`HttpConnectionManager ` config. .. note:: The management server responding to these endpoints must respond with a :ref:`DiscoveryResponse ` along with a HTTP status of 200. Additionally, if the configuration that would be supplied has not changed (as indicated by the version supplied by the Envoy client) then the management server can respond with an empty body and a HTTP status of 304. .. _config_overview_v2_ads: Aggregated Discovery Service ---------------------------- While Envoy fundamentally employs an eventual consistency model, ADS provides an opportunity to sequence API update pushes and ensure affinity of a single management server for an Envoy node for API updates. ADS allows one or more APIs and their resources to be delivered on a single, bidirectional gRPC stream by the management server. Without this, some APIs such as RDS and EDS may require the management of multiple streams and connections to distinct management servers. ADS will allow for hitless updates of configuration by appropriate sequencing. For example, suppose *foo.com* was mapped to cluster *X*. We wish to change the mapping in the route table to point *foo.com* at cluster *Y*. In order to do this, a CDS/EDS update must first be delivered containing both clusters *X* and *Y*. Without ADS, the CDS/EDS/RDS streams may point at distinct management servers, or when on the same management server at distinct gRPC streams/connections that require coordination. The EDS resource requests may be split across two distinct streams, one for *X* and one for *Y*. ADS allows these to be coalesced to a single stream to a single management server, avoiding the need for distributed synchronization to correctly sequence the update. With ADS, the management server would deliver the CDS, EDS and then RDS updates on a single stream. ADS is only available for gRPC streaming (not REST) and is described more fully in :ref:`xDS ` document. The gRPC endpoint is: .. http:post:: /envoy.service.discovery.v2.AggregatedDiscoveryService/StreamAggregatedResources See :repo:`discovery.proto ` for the service definition. This is used by Envoy as a client when .. code-block:: yaml ads_config: api_type: GRPC grpc_services: envoy_grpc: cluster_name: some_ads_cluster is set in the :ref:`dynamic_resources ` of the :ref:`Bootstrap ` config. When this is set, any of the configuration sources :ref:`above ` can be set to use the ADS channel. For example, a LDS config could be changed from .. code-block:: yaml lds_config: api_config_source: api_type: REST cluster_names: [some_xds_cluster] to .. code-block:: yaml lds_config: {ads: {}} with the effect that the LDS stream will be directed to *some_ads_cluster* over the shared ADS channel. .. _config_overview_v2_delta: Delta endpoints --------------- The REST, filesystem, and original gRPC xDS implementations all deliver "state of the world" updates: every CDS update must contain every cluster, with the absence of a cluster from an update implying that the cluster is gone. For Envoy deployments with huge amounts of resources and even a trickle of churn, these state-of-the-world updates can be cumbersome. As of 1.12.0, Envoy supports a "delta" variant of xDS (including ADS), where updates only contain resources added/changed/removed. Delta xDS is a gRPC (only) protocol. Delta uses different request/response protos than SotW (DeltaDiscovery{Request,Response}); see :repo:`discovery.proto `. Conceptually, delta should be viewed as a new xDS transport type: there is static, filesystem, REST, gRPC-SotW, and now gRPC-delta. (Envoy's implementation of the gRPC-SotW/delta client happens to share most of its code between the two, and something similar is likely possible on the server side. However, they are in fact incompatible protocols. :ref:`The specification of the delta xDS protocol's behavior is here `.) To use delta, simply set the api_type field of your :ref:`ApiConfigSource ` proto(s) to DELTA_GRPC. That works for both xDS and ADS; for ADS, it's the api_type field of :ref:`DynamicResources.ads_config `, as described in the previous section. .. _config_overview_v2_mgmt_con_issues: Management Server Unreachability -------------------------------- When an Envoy instance loses connectivity with the management server, Envoy will latch on to the previous configuration while actively retrying in the background to reestablish the connection with the management server. Envoy debug logs the fact that it is not able to establish a connection with the management server every time it attempts a connection. :ref:`connected_state ` statistic provides a signal for monitoring this behavior. .. _management_server_stats: Statistics ---------- Management Server has a statistics tree rooted at *control_plane.* with the following statistics: .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 connected_state, Gauge, A boolean (1 for connected and 0 for disconnected) that indicates the current connection state with management server rate_limit_enforced, Counter, Total number of times rate limit was enforced for management server requests pending_requests, Gauge, Total number of pending requests when the rate limit was enforced .. _subscription_statistics: xDS subscription statistics --------------------------- Envoy discovers its various dynamic resources via discovery services referred to as *xDS*. Resources are requested via :ref:`subscriptions `, by specifying a filesystem path to watch, initiating gRPC streams or polling a REST-JSON URL. The following statistics are generated for all subscriptions. .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 config_reload, Counter, Total API fetches that resulted in a config reload due to a different config init_fetch_timeout, Counter, Total :ref:`initial fetch timeouts ` update_attempt, Counter, Total API fetches attempted update_success, Counter, Total API fetches completed successfully update_failure, Counter, Total API fetches that failed because of network errors update_rejected, Counter, Total API fetches that failed because of schema/validation errors version, Gauge, Hash of the contents from the last successful API fetch control_plane.connected_state, Gauge, A boolean (1 for connected and 0 for disconnected) that indicates the current connection state with management server