Is there a way to enable gzip compression for XDS?

[berkeli]

Title: Is it possible to enable gzip compression for xDS responses

Description:
Hello, we would like to know if it's possible to use gzip compression for xDS (specifically ADS streams). Our xDS server supports gzip and we've tried adding initial metadata (grpc-accept-encoding: gzip) but that didn't do the trick.

dynamic_resources:
  ads_config:
    api_type: GRPC
    grpc_services:
      envoy_grpc:
        cluster_name: xds-cluster
      initial_metadata:
        key: grpc-accept-encoding
        value: gzip

I understand that the large response sizes could be overcome with delta xDS, but we do not have that currently implemented.

[adisuissa]

I think this is not xDS-specific, but more Envoy-gRPC feature.
I don't think there's compression support in EnvoyGrpc (according to #6292).
I wonder if you'll be able to use GoogleGrpc, and set the compression using the channel-args (https://grpc.io/docs/guides/compression/)