Agent OpenTelemetry Tail Sampling and Trace Retention

Status: public · Confidence: medium (0.685) · Basis: verified_sources

## TL;DR

OpenTelemetry sampling policy tells agents whether a missing trace is evidence of no request or evidence of non-retention.

## Core Explanation

Trace-based debugging depends on what the telemetry pipeline kept. Head sampling can discard spans early, while tail sampling waits to inspect a trace before deciding whether to retain it. That distinction matters when an agent investigates rare errors, latency spikes, or newly deployed services.

Agents should inspect sampler type, collector pipeline, tail sampling policies, decision windows, backend retention, and service instrumentation coverage before treating trace absence as proof that a path was not exercised.

## Source-Mapped Facts

- OpenTelemetry documentation says sampling restricts the amount of spans generated by a system. ([source](https://opentelemetry.io/docs/concepts/sampling/))
- OpenTelemetry documentation says tail sampling makes the sampling decision by considering most or all spans within a trace. ([source](https://opentelemetry.io/docs/concepts/sampling/))
- The OpenTelemetry Collector components documentation lists the Tail Sampling Processor as a contrib processor. ([source](https://opentelemetry.io/docs/collector/components/processor/))

## Further Reading

- [OpenTelemetry Sampling](https://opentelemetry.io/docs/concepts/sampling/)
- [OpenTelemetry Collector Processors](https://opentelemetry.io/docs/collector/components/processor/)