getTraceContext

The trace the current request belongs to — continued from the incoming W3C traceparent when there was one, originated by the runtime otherwise; in observe/dev builds, merged with the installed provider's answer (OBSERVE.server.trace). Same object for every read within the request, direct server-function calls included. For a render outside a request scope, the render's own trace, read within it (under its owner). undefined outside both, and on the client. Forward it downstream from a server function with getTraceContext()?.entries.traceparent.

Import

import { getTraceContext } from "@solidjs/web";

Type signature

function getTraceContext(): TraceContext | undefined;

Examples

await fetch(url, { headers: { ...getTraceContext()?.entries } });

Learn more

• Read trusted request context
• Follow a request into the browser
• Mutations and responses
• Middleware and API routes

Related types

TraceContext

The trace the current request belongs to — continued from the incoming W3C traceparent when there was one, originated by the runtime otherwise. Read with getTraceContext().

interface TraceContext {
  traceId: string;
  spanId: string;
  parentId?: string;
  sampled?: boolean;
  state?: string;
  baggage?: string;
  entries: Record<string, string>;
}

traceId

• Type: string

32 lowercase hex — the whole trace.

spanId

• Type: string

16 lowercase hex — this request's span: runtime-generated unless a provider supplied it.

parentId

• Type: string

The incoming parent span, when the request continued a trace.

sampled

• Type: boolean

The incoming traceparent sampled flag (bit 0); undefined when the runtime originated.

state

• Type: string

The incoming tracestate header, verbatim.

baggage

• Type: string

The incoming baggage header, verbatim.

entries

• Type: Record<string, string>

Named entries handed to the browser on the first response — emitted both as Server-Timing entries (<name>;desc="<value>") and, for HTML documents, as <meta name="<name>" content="<value>"> in the shell. The runtime fills traceparent; a provider adds its vendor pair (sentry-trace, baggage). Also what application code forwards downstream: fetch(url, { headers: { traceparent: entries.traceparent } }).

TraceProvider

An observer's answer for the trace a request belongs to, merged over the runtime's default derivation: fields it returns replace the derived ones (traceId/spanId from an APM's active span), its entries merge by name over the runtime's. Called once per request (or per render, for a render outside a request scope — request is then undefined), at shell flush or the first getTraceContext(), whichever comes first. Return undefined to leave the derivation alone.

type TraceProvider = (
  request: Request | undefined
) => Partial<TraceContext> | undefined;