Add Summary Data Point Support to the Exporter Collector

[davidwitten]

Is your feature request related to a problem? Please describe.

The OpenTelemetry Collector can take summary data points. However, there are currently no MetricKinds/Aggregators that support it. So, for the time being, the collector exporter is not able to export Summary data points, and I will put in a TODO.

Describe the solution you'd like

First, there has to be added support for this kind of data point, which could be a new aggregator.

Next, this has to be implemented in the CollectorMetricExporter, specifically in transformMetrics.ts.

Additional context

Summary data points are essentially lists of percentiles and corresponding values.

[dyladan]

@davidwitten are you volunteering or is this up for grabs?

[davidwitten]

@dyladan I'd be happy to do it, but I'm not sure what the next steps are. I noticed that in OpenTelemetry-go they just use the MinMaxLastSumCountAggregator and just set the 0th percentile to the min and the 100th percentile to the max. (code: here).

Should I do that as well? Or are there plans to add a new aggregator similar to the HistogramAggregator to return a SummaryDataPoint?

[dyladan]

I believe there are plans to add a histogram aggregator, but I can't remember who was working on that exactly. @vmarchaud maybe?

[vmarchaud]

I've indeed wrote one (althrough with an old spec) there.
However i believe the summary and histogram are two different aggregator because they don't exactly export the same values.

[davidwitten]

Are there any plans of making a Summary Aggregator? I noticed that in other languages, they just use MinMaxSumCount, and set the min to 0th percentile and max to 100th percentile. (E.g. in Java, Go), but that doesn't take advantage of the full utility of the Summary Data Point.

EDIT: I spoke to the OpenTelemetry-go repo, and this isn't planned.

Also @vmarchaud, I noticed that the HistogramAggregator isn't used for any metric (code here). What are the next steps for this? An option for the metric to use the HistogramAggregator vs. the default?

[davidwitten]

@vmarchaud, I see that the HistogramAggregator isn't used for any metric (code here). What are the next steps for this? An option for the metric to use the HistogramAggregator vs. the default?

[vmarchaud]

@davidwitten sorry i didn't see the previous mention. This aggregator is required by the spec but doesn't bind to any metrics by default. There is an example here on how to bind it to a metric

[davidwitten]

Ahh ok thanks!

[dyladan]

@davidwitten why did you close this?

[davidwitten]

@dyladan I added support for summary data points in PR #1320

[dyladan]

Ah I forgot that merged. Please make sure to always add a reason when closing an issue.