Retentions policy understand fro Graphite DB

Question

I have the below retentions policy mention in storage-schemas.conf file

[metrics]
pattern = ^metrics.api.*
retentions = 10s:5m,1m:1d,1h:30d,1d:1y,30d:10y

Below is my understanding this policy runs for the matched pattern starting with metrics.api*

1st: 10s:5m -> 1 or more times record inserted at 10s then its will take the latest record and maintain 1 datapoint , till 5min its maintains the history say suppose in 5m 5 datapoints added for the metrics key.

2nd:1m:1d -> this second run after the 5min overs for the same metrics key ,1 or more times record inserted at 1m then its will take the latest record and maintain 1 datapoint,till 1d its maintains the history say suppose in 1d 15 datapoints added for the metrics key.

so my question is what happens for these 2 retention is it will do the average 1st 5+15/2= 10 ? and get one average data point out of this 1st and 2nd rentions

--- its goes till 10years of data to be stored

can you please explain on the above retention polciy

Answer 1

aggregationMethod will be applied on this retention policy when switching boundaries. First retention - 10s:5m means Graphite will store 30 datapoints (every 10 seconds for last 5 minutes) in archive 0.

Please note, that it will always store these datapoints, even if no data arrived. In that case Graphite will put NULLs there.

Then next retention - 1m:1d means that every minute whisper will take 6 of these 10s datapoints from archive 0, apply average() function and store them in archive 1. But please note that Whisper will do so only if at least 3 (number of datapoints - 6 multiplied by xFilesFactor = 0.5) or more points in archive 0 have values (i.e. not NULLs). Otherwise Whisper decides that it has not enough data to propagate and put also NULL instead.

Etc - third retention 1h:30d means that 60 of datapoints from archive 1 will be aggregated using average function and propagated to archive 2, but only if at least 30 of them have value, etc.