<code>%DYNAMIC_METADATA(istio.mixer:status)%</code>.</p><p>Refer to the <a href=https://www.envoyproxy.io/docs/envoy/latest/configuration/observability/access_log#config-access-log-format-response-flags>Envoy response flags</a>
for details of response flags.</p><p>Common response flags are:</p><ul><li><code>NR</code>: No route configured, check your <code>DestinationRule</code> or <code>VirtualService</code>.</li><li><code>UO</code>: Upstream overflow with circuit breaking, check your circuit breaker config