Google Cloud Trace NodeJS for bundled applications - node.js

Question

I have a server side rendered web application using express that we were sending tracing info to Google using #google-cloud/trace-agent which worked fine. But THEN.... we bundled our application, and all trace information disappeared. We still see the requests in google cloud console, but now there are no child spans.
I scoured the documentation and stumbled upon this disappointing passage:
Tracing bundled or webpacked server code.
unsupported
The Trace Agent does not support bundled server code, so bundlers like webpack or #zeit/ncc will not work.
From: https://github.com/googleapis/cloud-trace-nodejs#tracing-bundled-or-webpacked-server-code
which I thought just meant that I need to start my own root spans... but that doesn't seem to be part of the API.
Does this mean I can't send spans in a bundled server? Is there a programmatic way to manually start root spans in express?

Answer 1

I ended up copying the middleware function from https://github.com/googleapis/cloud-trace-nodejs/blob/main/src/plugins/plugin-express.ts and adding it to my express app manually via app.use(...).
For completeness, the code is:
import { get as getTracer } from '#google-cloud/trace-agent';
import type { RootSpanOptions } from '#google-cloud/trace-agent/build/src/plugin-types';
import type { NextFunction, Request, Response } from 'express';
export function googleCloudTracing(request: Request, response: Response, next: NextFunction): void {
const tracer = getTracer();
const options: RootSpanOptions = {
name: request.path,
traceContext: tracer.propagation.extract(key => request.get(key)),
url: request.originalUrl,
method: request.method,
skipFrames: 1,
};
tracer.runInRootSpan(options, rootSpan => {
// Set response trace context.
const responseTraceContext = tracer.getResponseTraceContext(
options.traceContext!,
tracer.isRealSpan(rootSpan)
);
if (responseTraceContext) {
// This propagates the likes of tracer.constants.TRACE_CONTEXT_HEADER_NAME for cross-service tracing.
tracer.propagation.inject((k, v) => response.setHeader(k, v), responseTraceContext);
}
if (!tracer.isRealSpan(rootSpan)) {
next();
return;
}
tracer.wrapEmitter(request);
tracer.wrapEmitter(response);
const url = `${request.protocol}://${request.headers.host}${request.originalUrl}`;
rootSpan.addLabel(tracer.labels.HTTP_METHOD_LABEL_KEY, request.method);
rootSpan.addLabel(tracer.labels.HTTP_URL_LABEL_KEY, url);
rootSpan.addLabel(tracer.labels.HTTP_SOURCE_IP, request.ip);
response.on('finish', () => {
request.route?.path && rootSpan.addLabel('express/request.route.path', request.route.path);
rootSpan.addLabel(tracer.labels.HTTP_RESPONSE_CODE_LABEL_KEY, response.statusCode);
rootSpan.endSpan();
logger.info('Request tracing ended.');
});
next();
});
}