w3-trace-context

This is a Deno implementation of the W3 Trace Context recommendation. Specifically, it’s the 23 November 2021 version.

This class can be used to handle Trace Context, according to the W3 recommendation above. It also corresponds to the OpenTelemetry Context.

Usage

The W3TraceContext cannot be instantiated directly. Instead, it can be created from HTTP headers or created by passing it an IdGenerator

From HTTP Headers

const w3TraceContext = W3TraceContext.fromHeaders(requestHeaders);

From Scratch

const w3TraceContext = W3TraceContext.fromScratch({generator: new SimpleIdGenerator(), sampled: true}, traceState);

Trace Parent

Trace Parent information can be pulled directly from the context:

const traceId = w3TraceContext.traceId;
const parentId = w3TraceContext.parentId;

Trace State

Trace State information can be interacted with via methods that correspond to the functions available in the W3 Trace State module:

const getOtelState = w3TraceContext.getTraceStateValue('otel');
w3TraceContext.updateTraceStateValue('otel','1234');

While the TraceState object is immutable, the method calls on W3TraceContext that interact with trace state will update its own internal state. However, no mutation will occur to any externally reference TraceStates.

Deno module

This repository is available as a Deno module at https://deno.land/x/w3_trace_context