HTTP and TCP

Long name	Short name	Description
NoHealthyUpstream	UH	No healthy upstream hosts in upstream cluster in addition to 503 response code.
UpstreamConnectionFailure	UF	Upstream connection failure in addition to 503 response code.
UpstreamOverflow	UO	Upstream overflow (circuit breaking) in addition to 503 response code.
NoRouteFound	NR	No route configured for a given request in addition to 404 response code or no matching filter chain for a downstream connection.
UpstreamRetryLimitExceeded	URX	The request was rejected because the upstream retry limit (HTTP) or maximum connect attempts (TCP) was reached.
NoClusterFound	NC	Upstream cluster not found.
DurationTimeout	DT	When a request or connection exceeded max_connection_duration or max_downstream_connection_duration.

HTTP only

Long name	Short name	Description
DownstreamConnectionTermination	DC	Downstream connection termination.
FailedLocalHealthCheck	LH	Local service failed health check request in addition to 503 response code.
UpstreamRequestTimeout	UT	Upstream request timeout in addition to 504 response code.
LocalReset	LR	Connection local reset in addition to 503 response code.
UpstreamRemoteReset	UR	Upstream remote reset in addition to 503 response code.
UpstreamConnectionTermination	UC	Upstream connection termination in addition to 503 response code.
DelayInjected	DI	The request processing was delayed for a period specified via fault injection.
FaultInjected	FI	The request was aborted with a response code specified via fault injection.
RateLimited	RL	The request was ratelimited locally by the HTTP rate limit filter in addition to 429 response code.
UnauthorizedExternalService	UAEX	The request was denied by the external authorization service.
RateLimitServiceError	RLSE	The request was rejected because there was an error in rate limit service.
InvalidEnvoyRequestHeaders	IH	The request was rejected because it set an invalid value for a strictly-checked header in addition to 400 response code.
StreamIdleTimeout	SI	Stream idle timeout in addition to 408 or 504 response code.
DownstreamProtocolError	DPE	The downstream request had an HTTP protocol error.
UpstreamProtocolError	UPE	The upstream response had an HTTP protocol error.
UpstreamMaxStreamDurationReached	UMSDR	The upstream request reached max stream duration.
OverloadManagerTerminated	OM	Overload Manager terminated the request.
DnsResolutionFailed	DF	The request was terminated due to DNS resolution failure.
DropOverload	DO	The request was terminated in addition to 503 response code due to drop_overloads.