.. _config_overview_extension_configuration: Extension configuration ----------------------- Each configuration resource in Envoy has a type URL in the `typed_config`. This type corresponds to a versioned schema. If the type URL uniquely identifies an extension capable of interpreting the configuration, then the extension is selected regardless of the `name` field. In this case the `name` field becomes optional and can be used as an identifier or as an annotation for the particular instance of the extension configuration. For example, the following filter configuration snippet is permitted: .. code-block:: yaml name: front-http-proxy typed_config: "@type": type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager stat_prefix: ingress_http codec_type: AUTO rds: route_config_name: local_route config_source: resource_api_version: V3 api_config_source: api_type: GRPC transport_api_version: V3 grpc_services: envoy_grpc: cluster_name: xds_cluster http_filters: - name: front-router typed_config: "@type": type.googleapis.com/envoy.extensions.filters.http.router.v3.Router dynamic_stats: true In case the control plane lacks the schema definitions for an extension, `udpa.type.v1.TypedStruct` should be used as a generic container. The type URL inside it is then used by a client to convert the contents to a typed configuration resource. For example, the above example could be written as follows: .. code-block:: yaml name: front-http-proxy typed_config: "@type": type.googleapis.com/udpa.type.v1.TypedStruct type_url: type.googleapis.com/envoy.extensions.filters.network.http_connection_manager.v3.HttpConnectionManager value: stat_prefix: ingress_http codec_type: AUTO rds: route_config_name: local_route resource_api_version: V3 config_source: api_config_source: api_type: GRPC transport_api_version: V3 grpc_services: envoy_grpc: cluster_name: xds_cluster http_filters: - name: front-router typed_config: "@type": type.googleapis.com/udpa.type.v1.TypedStruct type_url: type.googleapis.com/envoy.extensions.filters.http.router.v3Router .. _config_overview_extension_discovery: Discovery service ^^^^^^^^^^^^^^^^^ Extension configuration can be supplied dynamically from an :ref:`xDS management server` using :ref:`ExtensionConfiguration discovery service`. The name field in the extension configuration acts as the resource identifier. For example, HTTP connection manager supports :ref:`dynamic filter re-configuration` for HTTP filters. Extension config discovery service has a :ref:`statistics ` tree rooted at *.extension_config_discovery.*. In addition to the common subscription statistics, it also provides the following: .. csv-table:: :header: Name, Type, Description :widths: 1, 1, 2 config_reload, Counter, Total number of successful configuration updates config_fail, Counter, Total number of failed configuration updates config_conflict, Counter, Total number of conflicting applications of configuration updates; this may happen when a new listener cannot reuse a subscribed extension configuration due to an invalid type URL.