@flarelog/sdk

---

@flarelog/sdk / workerFetch

Function: workerFetch()

workerFetch<T>(logger, handler): WorkerFetchHandler<T>

Defined in: frameworks/cf-workers.ts:59

Wrap a Cloudflare Worker fetch handler with automatic OTel instrumentation.

v2 — emits an OTel SERVER span for every request:

• Extracts W3C traceparent from incoming headers (or starts a new trace)
• Creates a SPAN_KIND_SERVER span: GET /api/users
• Sets http.request.method, url.path, url.full, http.response.status_code, etc.
• All logs emitted inside the handler carry the span's traceId + spanId
• Records exceptions on the span and sets span status
• Flushes telemetry via ctx.waitUntil() (with blocking fallback for tests)

Bypass: requests whose method is OPTIONS or HEAD, or whose URL pathname matches any entry in the logger's ignorePaths config, skip instrumentation entirely (no span, no flush). This keeps CORS preflight traffic and browser-driven noise like /favicon.ico out of your dashboard without requiring changes to your handler. See FlareLogConfig.ignorePaths.

Type Parameters

T

T = Response

Parameters

logger

FlareLog

handler

WorkerFetchHandler<T>

Returns

WorkerFetchHandler<T>

Examples

import { flarelog, workerFetch } from "@flarelog/sdk";

// No API key needed — defaults to console output
const logger = flarelog({});

export default {
  fetch: workerFetch(logger, async (request, env, ctx) => {
    return new Response("Hello");
  }),
};

Fan-out to Flarelog + Grafana

// wrangler.toml:
//   FLARELOG_API_KEY = "fl_your_key"
//   OTEL_EXPORTER_OTLP_ENDPOINT = "https://otlp-gateway-prod-eu-west-0.grafana.net"
//   OTEL_EXPORTER_OTLP_HEADERS = "Authorization=Basic <base64>"
const logger = flarelog({});
// → ships to both Flarelog dashboard and Grafana Cloud, plus console

Skip favicon and static assets

const logger = flarelog({
  apiKey: env.FLARELOG_API_KEY,
  ignorePaths: ["/favicon.ico", "/robots.txt", /^/static//],
});

export default {
  fetch: workerFetch(logger, async (request, env, ctx) => {
    return new Response("Hello");
  }),
};