Mechanism to explicitly flush stats to exporters

[arjantop]

Currently I see no way to push collected metrics to prometheus before program exit (especially in short batch programs), since views are reported periodically based on a timer.

What I have currently done is set view.SetReportingPeriod to something low and wait some duration and then perform the push.

[semistrict]

Prometheus natively doesn't really support this using the pull model. What seems like it would work would be to provide OpenCensus support for the Prometheus Push Gateway: https://github.com/prometheus/pushgateway.

Mind if we repurpose this as a feature request on the Prometheus exporter?

[arjantop]

You can currently push using the prometheus api (combined with opencensus). But if we get "native" push support in opencensus even better.

What I am doing currently:

• set up exporter with provided registry
• flush views lowering the view.SetReportingPeriod (a hack)
• user prometheus api to push

[semistrict]

Curious how you are pushing using the prometheus API. As I understand it, you register the exporter as an http.Handler and Prometheus scrapes it periodically. There isn't really a way to "force" Prometheus to scrape your app in a timely fashion. Sure, you can use SetReportingPeriod but all this does is change how often the page that Prometheus scrapes is updated. It doesn't guarantee that Prometheus will actually get the updated data.

[arjantop]

No, I do not register the endpoint, opencensus Prometheus exporter is just an interface between opencensus views and native prometheus registry. I am using the push api that is using the gateway.

So I pass in explicit registry in NewExporter: prometheus.Options{Registry: registry}

And then use the push api: push.FromGatherer(job, nil, promGateway, registry)

[semistrict]

Ah I see. I didn't realize that was possible. I will keep this open to add an example and document that usage.

I will also retitle to be closer to your original issue, namely that we need a way to flush exporters at process termination.

[songy23]

Duplicated of #862.