@fiberplane/hono-otel/dist/propagation.js

Hono middleware to forward OpenTelemetry traces to a local instance of @fiberplane/studio

import { context, propagation } from "@opentelemetry/api";
export function propagateFpxTraceId(request) {
    // HACK - We need to extract the traceparent from the request headers
    //        but we also need to set a dummy traceparent in the case that
    //        we are receiving an explicit trace-id to use from FPX.
    //
    // Extract fpx trace ID from request headers (if it exists)
    // and set it as a dummy active context
    //
    // TODO - Validate the id here using an otel helper, and warn if it is invalid
    const traceId = request.headers.get("x-fpx-trace-id");
    let activeContext = context.active();
    if (traceId) {
        activeContext = propagation.extract(context.active(), {
            traceparent: createTraceparentHeader(traceId),
        });
    }
    else {
        activeContext = propagation.extract(context.active(), request.headers);
    }
    return activeContext;
}
/**
 * Creates a traceparent header with a random span id
 *
 * @param traceId - The trace id to use in the traceparent header
 * @returns A traceparent header
 */
function createTraceparentHeader(traceId) {
    const version = "00"; // Version of the traceparent header
    // NOTE - A dummy span id like the following will be rejected by trace propagation API
    //        Look in the otel codebase for their regex - it filters out anything that's just 0 repeating
    //
    // const spanId = '0000000000000000'; // Dummy span ID
    //
    // HACK - Generate a random span id so we can spoof a proper trace parent
    //
    const spanId = generateSpanId();
    const traceFlags = "01"; // Trace flags (01 means sampled)
    return `${version}-${traceId}-${spanId}-${traceFlags}`;
}
/**
 * Generates a random 16-character hex string that is not all zeros
 *
 * @returns A random 16-character hex string
 */
function generateSpanId() {
    let spanId;
    do {
        spanId = [...Array(16)]
            .map(() => Math.floor(Math.random() * 16).toString(16))
            .join("");
    } while (/^[0]{16}$/.test(spanId));
    return spanId;
}