Add tracing sampling

[komuw]

In

otero/tracing.go

Lines 64 to 71 in bb23f8a

	provider := trace.NewTracerProvider(
	trace.WithBatcher(exporter), // use batch in prod.
	trace.WithResource(resource),
	trace.WithSpanProcessor(loggingSpanProcessor{}),
	// see: https://github.com/komuw/otero/issues/11
	// In prod, you should consider using the TraceIDRatioBased sampler with the ParentBased sampler.
	// sdktrace.WithSampler(sdktrace.AlwaysSample()),
	)

There's head-based sampling and tail-based sampling.

• https://news.ycombinator.com/item?id=37295097 (control-find sampling)
• https://opentelemetry.io/docs/concepts/sampling/
• https://github.com/open-telemetry/opentelemetry-collector-contrib/tree/main/processor/tailsamplingprocessor
• Discuss the possibility of deprecating the tail-based sampling processor open-telemetry/opentelemetry-collector-contrib#1797 (comment)
• https://github.com/open-telemetry/opentelemetry-collector/blob/main/docs/performance.md
• https://newrelic.com/blog/best-practices/open-telemetry-tail-sampling
• https://opentelemetry.io/docs/specs/otel/trace/tracestate-probability-sampling/

There is also filter processor that can be used in place of tail based sampling.

• https://tracetest.io/blog/opentelemetry-collectors-new-filter-processor
• https://github.com/open-telemetry/opentelemetry-collector-contrib/blob/main/pkg/ottl/contexts/ottllog/README.md