Envoy Proxy is an edge and service proxy for Cloud computing-native applications.
UH: no healthy upstream hosts.
UF: upstream connection failure.
UO: upstream overflow.
NR: no route configured.
URX: rejected because of upstream retry limit or maximum connection attempts reached.
Additionally, for HTTP:
DC: downstream connection termination.
LH: local service failed health check request.
UT: upstream request timeout.
LR: connection local reset.
UR: upstream remote reset.
UC: upstream connection termination.
DI: request processing was delayed for the specified period via fault injection.
FI: request was aborted with a specified response code via fault injection.
RL: request rate limited locally by the rate limiting filter.
UAEX: request was denied by the external authorisation service.
RLSE: request was rejected due to an error in the rate limit service.
IH: request was rejected with a 401 because it set an invalid value for a strictly-checked error.
SI: stream idle timeout, rejected with 408.
DPE: protocol error in downstream request.
UPE: protocol error un upstream response.
UMSDR: upstream request maximum stream duration reached.