An aggregate namespace who write data to it

[ning1875]

here is my usage ：promethues remote write to m3coordinator then write to m3dbnode 。And my question is that : Is it written to m3db after m3coordinator aggregation, or is it aggregated by m3db itself?

[arnikola]

It is aggregated in m3coordinator, and sent to aggregated namespaces in the dbnode

[ning1875]

It is aggregated in m3coordinator, and sent to aggregated namespaces in the dbnode
ok,get .

I have been looking at the code of m3coordinator recently, some places are not very understandable。
- namespace: metrics
type: aggregated
retention: 720h
resolution: 5m
If an aggregated namespace is specified in the configuration file like above. Does m3coordinator write all the aggregated results to m3dbnode, such as avg, last, max, min, or just write last? if all agg result has been written to dbnode ,how to query max ,min by query ? add a method tag like agg_type="max" ?
here are my understanding of how m3coordinator write to dbnode

consumeLocalMetric

m3/src/aggregator/aggregator/gauge_elem_gen.go

Line 210 in 07e7df8

func (e *GaugeElem) Consume(

-->consum -->processValueWithAggregationLock

m3/src/aggregator/aggregator/gauge_elem_gen.go

Line 403 in 07e7df8

func (e *GaugeElem) processValueWithAggregationLock(

then finally call this to write to dbnode

m3/src/cmd/services/m3coordinator/downsample/flush_handler.go

Line 174 in 07e7df8

err = w.handler.storage.Write(w.ctx, &storage.WriteQuery{

[robskillington]

Hey @ning1875 apologies for getting back to you late.

So right now by default the aggregation is always "last" value, you can use mapping rules to choose different aggregations:
https://docs.m3db.io/operational_guide/mapping_rollup/

This PR will then allow for adding tags per mapping rule so you can differentiate them as you need #2414.

We'll update the docs on this to make more clear.