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Late arriving records will be included in this metric, even if they are otherwise dropped due to the grace period having passed. Although we already expose a metric for the number of late dropped records, there is no way for a user to find out how late the record was. Including them in the staleness metrics may for one thing help users to set a reasonable grace period if they see that a large number of records are being dropped. Another slight difference with the concept of late records This metric is related but ultimately orthogonal to the concept of late-ness. One difference for example is that they are dropped based on stream time, whereas this metric is always reported with respect to the current time. The stream-time may lag the system time in low traffic, for example, or when all records are considerably delayed. This might mean the user sees no dropped records even though the staleness is large. 

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