xDS requests include a node proto with an arbitrarily large metadata field. This causes a problem if this metadata is a large JSON since it is sent for every EDS request. The proposal is to omit node field in a gRPC stream after the first request. Most gRPC servers can save some state per stream, so they can store the node in the local scope. In fact, this optimization is already applied for ALS and metrics services, so it seems like a gap in xDS.

cc @htuch