Clustering - Cannot read property 'responses' of undefined

https://github.com/siimon/prom-client/blob/master/lib/cluster.js#L159

I am attempting run prometheus in an application that collects metrics for calls within koa middleware

But I am finding that this line

const request = requests.get(message.requestId);

returns undefined, causing line 159 to throw the error Cannot read property 'responses' of undefined

Its also worth mentioning I’m running metrics through a node proxy server and collecting metrics in the middleware itself - if i guard on the presence of request, it appears to work as expected

if (request) {
  message.metrics.forEach(registry => request.responses.push(registry));
  request.pending--;
  // etc
}

The middleware is mounted at /api where i’m using promClient.Histogram to time calls

I’m afraid I don’t understand the code well enough to understand why the request is undefined. Is anyone available to walk me through this?

[edvardchen]

I had encountered same issue. It turned out that my worker script imported two copy of module prom-client

@montykamath

[zbjornson]

There’s no state like that, no. If you have a full repro that you can post, I’ll try to take a look.