Changed

• Metric SDK export.ExportKind, export.ExportKindSelector types have been renamed to aggregation.Temporality and aggregation.TemporalitySelector respectively to keep in line with current specification and protocol along with built-in selectors (e.g., aggregation.CumulativeTemporalitySelector, ...). (#2274)
• The Metric Exporter interface now requires a TemporalitySelector method instead of an ExportKindSelector. (#2274)
• Metrics API cleanup. The metric/sdkapi package has been created to relocate the API-to-SDK interface:
  • The following interface types simply moved from metric to metric/sdkapi: Descriptor, MeterImpl, InstrumentImpl, SyncImpl, BoundSyncImpl, AsyncImpl, AsyncRunner, AsyncSingleRunner, and AsyncBatchRunner
  • The following struct types moved and are replaced with type aliases, since they are exposed to the user: Observation, Measurement.
  • The No-op implementations of sync and async instruments are no longer exported, new functions sdkapi.NewNoopAsyncInstrument() and sdkapi.NewNoopSyncInstrument() are provided instead. (#2271)
• Update the SDK BatchSpanProcessor to export all queued spans when ForceFlush is called. (#2080, #2335)

Added

• Add the "go.opentelemetry.io/otel/exporters/otlp/otlpmetric/otlpmetricgrpc".WithGRPCConn option so the exporter can reuse an existing gRPC connection. (#2002)
• Added a new schema module to help parse Schema Files in OTEP 0152 format. (#2267)
• Added a new MapCarrier to the go.opentelemetry.io/otel/propagation package to hold propagated coss-cutting concerns as a map[string]string held in memory. (#2334)