Metrics not working?

[djMax]

I am trying to expose Prometheus metrics for my services. The open source base module is @gasbuddy/service, and the relevant code:

App startup: https://github.com/gas-buddy/service/blob/main/src/express-app/app.ts#L37
On listen: https://github.com/gas-buddy/service/blob/main/src/express-app/app.ts#L301

And when I make a counter and increment it:
https://github.com/gas-buddy/service/blob/main/__tests__/fake-serv/src/routes/index.ts#L4

I would expect that getting metrics from the metrics endpoint would return a counter. But it does not, it returns a blank object.

When I print the collection result, I see this:

{"resourceMetrics":{"resource":{"attributes":{}},"scopeMetrics":[{"scope":{"name":"fake-serv","version":""},"metrics":[]}]},"errors":[]}

My counter is not there nor is a value for it. Any idea what I'm doing wrong?

[djMax]

It's not entirely clear to me what opentelemetry provides in this instance - perhaps I would be better off just using prom-client?

[djMax]

I think I've figured it out - if you add metrics BEFORE the exporter has been added as a metric reader, they will not ever be collected. This definitely seems like a bug, if people agree I can try and file one.

[legendecas]

This is designed as intended. When no metric reader / views are registered, the SDK has no defaults on how to configure the metric instruments with proper aggregation and aggregation temporality.

Before registering metric instruments to the meter of the MeterProvider, one should properly configure the MeterProvider first.

[djMax]

At the very least this seems like a documentation and/or diagnostic logging bug. It's certainly not obvious that it should work this way (I don't think it actually should work this way - it should "pend" those adds until the provider is configured, or it should throw an error, or SOMETHING. Because silently breaking is super wrong)