Can't get active span in Express instrumentation.

[ScottChapman]

I followed the very simple instrumentation instructions:

const { NodeTracerProvider } = require('@opentelemetry/sdk-trace-node');
const { registerInstrumentations } = require('@opentelemetry/instrumentation');
const { HttpInstrumentation } = require('@opentelemetry/instrumentation-http');
const { ExpressInstrumentation } = require('@opentelemetry/instrumentation-express');

const provider = new NodeTracerProvider();
provider.register();

registerInstrumentations({
  instrumentations: [
    // Express instrumentation expects HTTP layer to be instrumented
    new HttpInstrumentation(),
    new ExpressInstrumentation(),
  ],
});

And in my express code I am trying to get the active span:

app.get("/api/results/:id", async (req, res) => {
  const localSpan = opentelemetry.trace.getActiveSpan();

But it ends up being null??

[faranak-cs]

I am facing the same issue: TypeError: Cannot read properties of undefined (reading 'spanContext'). The value is undefined:

app.get("/data", async (req, res) => {
  try {
    if (req.query["fail"]) {
      throw new Error("A really bad error :/");
    }
    const apiResponse = await axios.get("http://localhost:8090/user");
    res.json(apiResponse.data);
  } catch (error) {
    const activeSpan = api.trace.getSpan(api.context.active());
    const traceId = activeSpan.spanContext().traceId;

    // Combine log  with trace
    console.error(`Critical Error, traceId: ${traceId}`);
    res.sendStatus(500);
  }
});

const { PrometheusExporter } = require("@opentelemetry/exporter-prometheus");
const { OTLPTraceExporter } = require("@opentelemetry/exporter-trace-otlp-http");
const { registerInstrumentations } = require("@opentelemetry/instrumentation");
const { ExpressInstrumentation } = require("@opentelemetry/instrumentation-express");
const { HttpInstrumentation } = require("@opentelemetry/instrumentation-http");
const { Resource } = require("@opentelemetry/resources");
const { MeterProvider } = require("@opentelemetry/sdk-metrics");
const {
  NodeTracerProvider,
  SimpleSpanProcessor,
  ConsoleSpanExporter,
} = require("@opentelemetry/sdk-trace-node");
const { ATTR_SERVICE_NAME } = require("@opentelemetry/semantic-conventions");

const init = function (serviceName, metricPort) {
  // Define metrics
  const metricExporter = new PrometheusExporter({ port: metricPort }, () => {
    console.log(
      `scrape: http://localhost/:${metricPort}${PrometheusExporter.DEFAULT_OPTIONS.endpoint}`
    );
  });

  // Create meter provider
  const meterProvider = new MeterProvider({
    readers: [metricExporter],
  });

  // Get meter
  const meter = meterProvider.getMeter(serviceName);

  // Define traces
  const traceExporter = new ConsoleSpanExporter();
  const processor = new SimpleSpanProcessor(traceExporter);

  // Create trace provider
  const provider = new NodeTracerProvider({
    resource: new Resource({
      [ATTR_SERVICE_NAME]: serviceName,
    }),
    spanProcessors: [processor],
  });

  provider.register();

  // Register instrumentations
  registerInstrumentations({
    instrumentations: [new HttpInstrumentation(), new ExpressInstrumentation()],
  });

  // Get tracer
  const tracer = provider.getTracer(serviceName);

  // Return meter & tracer
  return { meter, tracer };
};

module.exports = init;

[faranak-cs]

Hi @pichlermarc, please guide. Thanks

[raphael-theriault-swi]

This is a known issue due to the express instrumentation not creating proper spans for response handlers and not setting the active span in the context.

Relates to

• @opentelemetry/instrumentation-express handler does not run in correct context #2022
• @opentelemetry/instrumentation-express handler does not account for async work #2023
• Auto instrumentation of express app is not sending exception event in trace #2146
• express instrumentation - span end prematurely for non-middleware instrumentations #2442
• Can't update span name when using OpenTelemetry Express Instrumentation for Node.js #2469

[ScottChapman]

Oooph. One thing I considered doing was implement a requestHook for the express instrumentation and attach the span to the request. Felt pretty hacky though

[faranak-cs]

Any solutions for the time being? @raphael-theriault-swi
Thanks

[raphael-theriault-swi]

Oooph. One thing I considered doing was implement a requestHook for the express instrumentation and attach the span to the request. Felt pretty hacky though

Yeah it's not great, but at the moment I don't see a better way to work around this until it's fixed in the instrumentation.

[faranak-cs]

Thanks a lot, @raphael-theriault-swi

[faranak-cs]

Oooph. One thing I considered doing was implement a requestHook for the express instrumentation and attach the span to the request. Felt pretty hacky though

Hi @ScottChapman, can you explain more about your solution?

[ScottChapman]

Oooph. One thing I considered doing was implement a requestHook for the express instrumentation and attach the span to the request. Felt pretty hacky though

Hi @ScottChapman, can you explain more about your solution?

Yea so look here Basically you would just add a property to the request object and set it to the span.

That seems to be fine it you are doing manual instrumentation.

But I am not sure if you can add a request hook to the instance that is created during auto-instrumentation??

[ScottChapman]

In the short term are folks having better success with an express alternative (like fastify or others)?
In my sample app I created a new running span, and I can see logs show the trace and span IDs, but the span doesn't appear under any trace. which is weird.