immutable state specified at configuration load time (e.g., through xDS).
e.g. the subset load balancer uses the metadata from the route entry corresponding to the weighted cluster to select appropriate endpoints in a cluster
Incoming config metadata (via xDS) is converted to class objects at config load time. Filters can then obtain a typed variant of the metadata at runtime (per request or connection)
allows HTTP filters to have virtualhost/route-specific configuration in addition to a global filter config common to all virtual hosts.
Dynamic state is generated per network connection or per HTTP stream, and can be mutable
contextual properties provided by Envoy during request and connection processing. They are named by a dot-separated path (e.g. request.path), have a fixed type (e.g. string or int), and may be absent or present depending on the context.
The matching API is designed as a tree structure to allow for sublinear matching algorithms for better performance
some filter might case unexpected behavior on data path