Overview

A Context carries trace state (the current Span) and Baggage across API boundaries and through your application. You rarely interact with it directly; the inSpan functions and propagators manage it for you.

When you need Context directly

• Custom propagation: extracting/injecting context from non-HTTP transports
• Manual span parenting: creating a span as a child of a specific context
• Baggage access: reading or modifying baggage entries

Quick example

import OpenTelemetry.Context
import OpenTelemetry.Context.ThreadLocal

-- Read the current span from thread-local context:
ctx <- getContext
case lookupSpan ctx of
  Just span -> addAttribute span "custom.key" (toAttribute "value")
  Nothing   -> pure ()

-- Attach baggage to the current context:
adjustContext (insertBaggage myBaggage)

Thread-local context

In most applications, context is stored in a thread-local variable managed by OpenTelemetry.Context.ThreadLocal. The inSpan functions automatically push and pop spans from this thread-local context.

Spec reference

https://opentelemetry.io/docs/specs/otel/context/