Release v1.21.0

v1.21.0 (2023-05-17)

Context

• No changes.

Traces

• No changes.

Metrics

• Add experimental histogram advice API.
  (#3216)
• Recommended non-prefixed units for metric instrument semantic conventions.
  (#3312)
• Recommended cardinality limits to protect metrics pipelines against
  excessive data production from a single instrument.
  (#2960)
• Add links to the JMX APIs that are the JVM runtime metric sources.
  (#3463)

Logs

• Clarify parameters for emitting a log record.
  (#3345)
• Drop logger include_trace_context parameter.
  (#3397)
• Clarify how ObservedTimestamp field is set if unspecified
  (#3385)
• Mark logs bridge API / SDK as stable.
  (#3376)
• Mark LogRecord Environment Variables as stable.
  (#3449)

Resource

• No changes.

Semantic Conventions

• The Semantic Conventions have moved to a separate repository
  github.com/open-telemetry/semantic-conventions.
  There will be no future semantic conventions release from this repository.
  (#3489)

Compatibility

• Mark OpenCensus compatibility spec as stable
  (#3425)

OpenTelemetry Protocol

• No changes.

SDK Configuration

• Lay initial groundwork for file configuration
  (#3360)
• Move file configuration schema to opentelemetry-configuration.
  (#3412)
• Move sdk-configuration.md and sdk-environment-variables.md
  to /specification/configuration/.
  (#3434)

Telemetry Schemas

• No changes.

Common

• Add log entries to specification README.md contents.
  (#3435)

Supplementary Guidelines

• Add guidance to use service-supported propagation formats as default for AWS SDK client calls.
  (#3212)

New Contributors

• @sebastien-rosset made their first contribution in #3194
• @roberttoyonaga made their first contribution in #3463
• @lzchen made their first contribution in #3475

Full Changelog: v1.20.0...v1.21.0