⚠️ Notice ⚠️

This update is a breaking change of the unstable Metrics API. Code instrumented with the go.opentelemetry.io/otel/metric will need to be modified.

Added

• Add metrics exponential histogram support. New mapping functions have been made available in sdk/metric/aggregator/exponential/mapping for other OpenTelemetry projects to take dependencies on. (#2502)
• Add Go 1.18 to our compatibility tests. (#2679)
• Allow configuring the Sampler with the OTEL_TRACES_SAMPLER and OTEL_TRACES_SAMPLER_ARG environment variables. (#2305, #2517)
• Add the metric/global for obtaining and setting the global MeterProvider. (#2660)

Changed

• The metrics API has been significantly changed to match the revised OpenTelemetry specification. High-level changes include:

  • Synchronous and asynchronous instruments are now handled by independent InstrumentProviders. These InstrumentProviders are managed with a Meter.
  • Synchronous and asynchronous instruments are grouped into their own packages based on value types.
  • Asynchronous callbacks can now be registered with a Meter.

  Be sure to check out the metric module documentation for more information on how to use the revised API. (#2587, #2660)

Fixed

• Fallback to general attribute limits when span specific ones are not set in the environment. (#2675, #2677)