The metrics2 system was implemented to deal with persistent sources. ContainerMetrics is an ephemeral source, and so it causes problems. Specifically, the ContainerMetrics only reports metrics once after the container has been stopped. This behavior is a problem because the metrics2 system can ask sources for reports that will be quietly dropped by the sinks that care. (It's a metrics2 feature, not a bug.) If that final report is silently dropped, it's lost, because the ContainerMetrics won't report anything else ever anymore.