feat: Allow specifying aggregation for SynchronousInstruments

[joshwestbrook]

Our application has a handful of legacy API endpoints that far exceed the default explicit histogram buckets, and currently there is no way to override the default buckets for histograms. Allowing the aggregation to be explicitly provided for SyncrhonousInstruments means we will be able to get data that is actually representative of our API response times.

[kaylareopelle]

Hi @joshwestbrook, thanks for this PR and for your patience!

If I'm understanding your situation, I think the add_view method might suit your needs.

In this example below, a view is added to the http.server.request.duration metric to override the default boundaries by creating a new ExplicitBucketHistogram with the desired boundaries passed as an arg:

OpenTelemetry.meter_provider.add_view(
  'http.server.request.duration', 
   aggregation: 
     OpenTelemetry::SDK::Metrics::Aggregation::ExplicitBucketHistogram.new(
       boundaries: [
         0.005, 0.01, 0.025, 0.05, 0.075, 0.1, 0.25, 0.5, 0.75, 1, 2.5, 5, 7.5, 10
       ]
     )
   )

histogram = APP_METER.create_histogram(
  'http.server.request.duration', 
  unit: 's', 
  description: 'Duration of HTTP server requests.'
)

Could you give this a try?

Here's more documentation on Metric Views in OpenTelemetry.

[joshwestbrook]

Hey Kayla! I appreciate the suggestion, I didn't realize views were ready to be used yet! I'll give that a shot and follow back up with you 😄