Migrate collector's metrics from OC to OpenTelemetry

[pavolloffay]

Currently, the collector uses OpenCensus API for internal observability

opentelemetry-collector/observability/observability.go

Line 25 in 0e1b2e3

"go.opencensus.io/stats"

.

These metrics should be probably migrated to OpenTelemetry API.

Jaeger storage components use abstract metrics API and so we need to export these metrics in Jaeger OTEL collector e.g.

https://github.com/jaegertracing/jaeger/blob/bf870d9e2bffaf4758045919446be75ac9fc9783/cmd/opentelemetry-collector/app/exporter/cassandra/exporter.go#L31.

Are there plans to migrate to OpenTelemetry metrics? In Jaeger we want to avoid first creating OC adapter and then OTEL once this repo migrates. I can submit a PR to port the metrics to OTEL API.

[yurishkuro]

This would also provide the needed dogfooding for OTel SDK.

[bogdandrutu]

@yurishkuro completely agree, we are waiting for 2 things:

1. The ability to use labels from the correlation-context.
2. The ability to configure Views - allow us to configure which labels from the correlation-context to use.

If we don't have these two things we need to manually propagate/retrieve these values every time we do a report. Which may be possible if we do have couple of helper functions. So probably the main missing feature is to support changing the default aggregations for some instruments like for distributions we don't want just minmaxsumcount we want a histogram.

• @jmacd to help correct me if we can already do the histogram thing.

[yurishkuro]

Why do you need context labels in the collector? Sounds a bit like nice to have, not a showstopper.

[bogdandrutu]

I think I also tried to explain myself that we have the solution to use helper functions, but let me describe the design a bit:

• In the pipeline we want to record at every step metric broken down by the "receiver" so we add receiver to the context to propagate it in the pipeline instead of having it as an explicit argument. So we can have helper functions that just retrieve that from the context and use it in the metrics as labels.

And as I explained is not a showstopper, the current blocker is the ability to configure the aggregation for the distribution to be histogram vs minmaxsumcount, and probably a nice to have is the ability to select the labels for the aggregator (again not a showstopper).

[bogdandrutu]

@pavolloffay to answer your question, we do want to use opentelemetry metrics. probably tracing as well :)

[pavolloffay]

thanks @bogdandrutu. I can open a PR to port the metrics.

Is there any issue in opentelemetry-go for:

So probably the main missing feature is to support changing the default aggregations for some instruments like for distributions we don't want just minmaxsumcount we want a histogram.

[bogdandrutu]

I think the missing thing is this otep open-telemetry/oteps#89

[tigrannajaryan]

@bogdandrutu I think I remember some recent work that you did on this and changed telemetry to use Otel API instead of OpenCensus. Is that correct? If so I can close this.