EDS + endpoint slow start Support

[zhshw]

Description:
There are many types of programs that start slowly and require the flow control of the Pod Endpoint.
envoy supports slow start config feature

[arkodg]

@zhshw can you please elaborate on why EDS is needed for the slow start feature ?
https://www.envoyproxy.io/docs/envoy/latest/api-v3/config/cluster/v3/cluster.proto#config-cluster-v3-cluster-slowstartconfig

We build static clusters in this project, and when a service endpoint changes, it will be reconciled by the controller, translated into an xds cluster and then, only the updated cluster will be pushed to envoy via delta xds

[zhshw]

@arkodg For example, many Java applications start very slowly, requiring a flow warm-up process.
In the process of practicing cloud nativeness, many projects implement traffic warmup in various ways,
so aws ALb takes the lead in supporting and envoy implements Istio also supports configuration changes
service -> Pod endpoints -> lbEndpoints , If you have configured slowstart in the cluster，The new lbendpoint will enter the warm-up mode。

The clusterip is basically unchanged
current code
return &ir.RouteDestination{ Host: service.Spec.ClusterIP, Port: uint32(*backendRef.Port), Weight: weight, }, weight

For large services, the service clusterip will add one request hop of NAT. The five tuples of the clusterip are limited by the number of ports on the node

[arkodg]

there is no strong use case for EDS yet

but the slow start feature is a valid use case that I believe is separate. It is however blocked by #35 . Is this something you could help with @zhshw ?

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.

[arkodg]

reopening this issue, as the use case for incorporating EDS is to seamlessly update endpoints without disrupting existing upstream connections associated with the Cluster.

[zirain]

FYI, EDS will be helpful on case like istio/istio#43575