[mwear]

Description

Related to #2127

This adds meter_provider support to opentelemetry-config. This might be a little early as work for some of the options is still under way in the SDK.

Like logs in #2439, the metrics gems are soft dependencies, and only configured values are passed to the SDK. Omitted settings fall back to SDK defaults.

The SDK drops data for views without an aggregation, so config resolves a view's default aggregation from selector.instrument_type, and skips views that don't set one.

Some settings aren't supported by the SDK yet. They're skipped with a warning, and several have open PRs:

• stream.attribute_keys: the SDK merges these into the measurement attributes instead of filtering them (fix(metrics_sdk)!: add the attribute_keys filter for view #2426)
• default_histogram_aggregation (feat(metrics_sdk): support OTEL_EXPORTER_OTLP_METRICS_DEFAULT_HISTOGRAM_AGGREGATION env var #2389)
• stream.description (feat(metrics_sdk): add reservoir and description option for view #2427)
• producers (feat(metrics): add metrics producer and filter #2418)
• temporality_preference, pull readers, otlp_grpc, otlp_file/development, stream.name, selector.meter_schema_url, and per-instrument-kind cardinality_limits

I'll wire these up as the SDK support lands.

Changes

• Build an SDK MeterProvider from meter_provider, with periodic readers, console and otlp_http exporters, views, and exemplar_filter
• Config.install registers the meter provider as OpenTelemetry.meter_provider, upgrading the default proxy, and attaches fork hooks so periodic readers restart in forked processes
• Treat the metrics SDK and OTLP metrics exporter as optional, skipping with a warning when they aren't loaded
• Docs

Authorship

• I, a human, wrote this pull request description myself.