@ -166,34 +166,27 @@ the management server only needs to respond to the latest
Resource hints
^^^^^^^^^^^^^^
The :ref:`resource_names <envoy_api_field_DiscoveryRequest.resource_names>` specified in the :ref:`DiscoveryRequest <envoy_api_msg_DiscoveryRequest>` are a hint.
Some resource types, e.g. `Clusters` and `Listeners` may
specify an empty :ref:`resource_names <envoy_api_field_DiscoveryRequest.resource_names>` list, since a client such as Envoy is interested in
learning about all the :ref:`Clusters (CDS) <envoy_api_msg_Cluster>` and :ref:`Listeners (LDS) <envoy_api_msg_Listener>`
that the management server(s) know about corresponding to its node
identification. Other resource types, e.g. :ref:`RouteConfiguration (RDS) <envoy_api_msg_RouteConfiguration>`
and :ref:`ClusterLoadAssignment (EDS) <envoy_api_msg_ClusterLoadAssignment>`, follow from earlier
CDS/LDS updates and Envoy is able to explicitly enumerate these
resources.
Envoy will always set the LDS/CDS resource hints to empty and it is expected that the management
server will provide the complete state of the LDS/CDS resources in each response. An absent
`Listener` or `Cluster` will be deleted. Other xDS clients may specify explicit LDS/CDS resources as
resource hints, for example if they only have a singleton listener and already know its name from
some out-of-band configuration.
For EDS/RDS, the management server does not need to supply every
requested resource and may also supply additional, unrequested
resources. :ref:`resource_names <envoy_api_field_DiscoveryRequest.resource_names>` is only a hint. Envoy will silently ignore
any superfluous resources. When a requested resource is missing in a RDS
or EDS update, Envoy will retain the last known value for this resource
except in the case where the `Cluster` or `Listener` is being
warmed. See :ref:`Resource Warming <xds_protocol_resource_warming>` section below on
the expectations during warming. The management server may be able to
infer all the required EDS/RDS resources from the :ref:`node <envoy_api_msg_Core.Node>`
identification in the :ref:`DiscoveryRequest <envoy_api_msg_DiscoveryRequest>`, in which case this hint may
be discarded. An empty EDS/RDS :ref:`DiscoveryResponse <envoy_api_msg_DiscoveryResponse>` is effectively a
nop from the perspective of the respective resources in the Envoy.
The :ref:`resource_names <envoy_api_field_DiscoveryRequest.resource_names>` specified in the :ref:`DiscoveryRequest
<envoy_api_msg_DiscoveryRequest>` are a hint about what resources the client is interested in.
For :ref:`Listener Discovery Service (LDS) <envoy_api_msg_Listener>` and :ref:`Cluster Discovery Service (CDS)
<envoy_api_msg_Cluster>`, Envoy will always set the resource hints to empty, in which case the server should use
site-specific business logic to determine the full set of resources that the client is interested in, typically based on
the client's node identification. However, other xDS clients may specify explicit LDS/CDS resources as resource hints, for
example if they only have a singleton listener and already know its name from some out-of-band configuration. For EDS/RDS, the
resource hints are required.
When the resource hints are specified, the management server must supply the requested resources if they exist. The client will
silently ignore any supplied resources that were not explicitly requested. When the client sends a new request that changes
the *resource_names* list, the server must resend any newly requested resource, even if it previously sent it without having
been asked for it and the resource has not changed since that time.
For LDS and CDS, it is expected that the management server will provide the complete state of the LDS/CDS resources in each
response; an absent `Listener` or `Cluster` will be deleted. For RDS or EDS, when a requested resource is
missing, Envoy will retain the last known value for this resource except in the case where the `Cluster` or `Listener` is being
warmed. See :ref:`Resource Warming <xds_protocol_resource_warming>` section below on the expectations during warming.
An empty EDS/RDS :ref:`DiscoveryResponse <envoy_api_msg_DiscoveryResponse>` is effectively a nop from the perspective of the
respective resources in the Envoy.
When a `Listener` or `Cluster` is deleted, its corresponding EDS and
RDS resources are also deleted inside the Envoy instance. In order for
data-plane-api(CircleCI)
5 years ago