Setup correct aggregation values when submitting metrics to librato.

[ryandotsmith]

You need to specify how librato down-samples data over time, currently there are options for: sum, average, max. L2met metrics like sum and count should be count aggregated over time while things like mean should be averaged. When it comes to percentiles, I am not sure what to do here. Perhaps the max function would be the best.

[BRMatt]

Please correct me if my understanding librato's aggregation is off, but I think it might be best to sum both the sum and count metrics, as in both cases you want the sum of all values for a time period, not the number of times librato received the metric. e.g.

• An app logs 10 measurements 1...10, at 12 second intervals over the space of 2 minutes
• If working in a 60 second period then the first 5 measurements cause l2met to send metric.sum=15, metric.count=5
• In the second period the final 5 measurements cause l2met to send metric.sum=40, metric.count=5

When it comes to aggregating the two periods into one, we should see metric.sum=55, metric.count=10. If the aggregation of metric.count were count then I think we'd see "2" rather than "10".

WRT to percentiles, I think max is best, as you want to know the worst case for each percentile, however I'm not sure about mean, median and last.

Thoughts?

• .count -> sum
• .sum -> sum
• .max -> max
• .min -> min
• .p99 -> max
• .p95 -> max
• .mean -> average/max
• .median -> average/max
• .last -> average/max

[ryandotsmith]

I am actually not sure if l2met should be responsible for this. I am thinking that librato-dash will take care of all this type of data.