Extension configuration

Each configuration resource in Envoy has a type URL in the typed_config. This type corresponds to a versioned schema. The type URL uniquely identifies an extension capable of interpreting the configuration. The name field is 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:

extensions-demo.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, xds.type.v3.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:

extensions-demo-with-type-url.yaml

      - name: front-http-proxy
        typed_config:
          "@type": type.googleapis.com/xds.type.v3.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
              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/xds.type.v3.TypedStruct
                type_url: type.googleapis.com/envoy.extensions.filters.http.router.v3.Router
                value:
                  dynamic_stats: true

Discovery service

Extension configuration can be supplied dynamically from an xDS management server using ExtensionConfiguration discovery service. The name field in the extension configuration acts as the resource identifier.

Listener filters

For Listener filters, the discovery service configuration is: dynamic listener filter re-configuration. The dynamic listener filter config is only supported in TCP listeners. If the dynamic configuration is missing, the connection will be rejected until a valid config is updated.

Network filters

For downstream network filters, the discovery service configuration is: dynamic filter re-configuration. If the dynamic configuration is missing, the connection will be rejected until a valid config is updated. When a filter configuration updates, the new configuration will only apply to new connections, existing connections will keep using the older filter configuration.

HTTP filters

For HTTP filters, HTTP connection manager supports dynamic filter re-configuration. If the configuration is missing a local HTTP response with ‘500’ status code will be returned.

Statistics

In addition to the statistics supported for xDS subscriptions, the following statistics are supported for listener filters, downstream network filters, and HTTP filters, rooted at extension_config_discovery.<stat_prefix>.<extension_config_name>.

• For TCP listener filters, the value of <stat_prefix> is tcp_listener_filter.

• For downstream network filters, the value of <stat_prefix> is network_filter.

• For upstream network filters, the value of <stat_prefix> is upstream_network_filter.

• For downstream HTTP filters, the value of <stat_prefix> is http_filter.

• For upstream HTTP filters, the value of <stat_prefix> is upstream_http_filter.

Name	Type	Description
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.

Additionally, the following statistics are supported to indicate that a connection was closed due to a missing configuration, rooted at listener.<address> (or listener.<stat_prefix>. if stat_prefix is non-empty).

Name	Type	Description
extension_config_missing	Counter	Total connections closed due to missing listener filter extension configuration
network_extension_config_missing	Counter	Total connections closed due to missing network filter extension configuration