Stackdriver exporter does not upload metrics when used in GCP Function and there is no way to wait on it

[ckenna]

What version of OpenCensus are you using?

0.1.0

What version of Node are you using?

18.7.0

What did you do?

If possible, provide a recipe for reproducing the error.

Have code that looks like this inside a Google Cloud Function:

functions.cloudEvent('lg-stock-check', async () => {

  // Omitted code...

  const exporter = new StackdriverStatsExporter({
    projectId: projectId,
    period: 60 * 1000,
    onMetricUploadError: (err) => {
      log.error(log.entry({err: err}, "Error uploading metrics: " + err));
    },
  });
  globalStats.registerExporter(exporter);

  // Omitted code...

    await logMetricsFunction();  // Log out some metrics here.
    await exporter.export();

    // This is horrible, but the exporter calls:
    // https://github.com/census-instrumentation/opencensus-node/blob/04ae44cf8875c59b99ea65ed2135b6bc816b49b4/packages/opencensus-exporter-stackdriver/src/stackdriver-monitoring.ts#L182
    // Which is an async function we cannot get the promise for.
    // So sleeping a bit to try and let it finish.
    await sleep(30000); // This still doesn't help.

    exporter.stop();
    globalStats.unregisterExporter(exporter);
  } catch (err) {
    console.error("Error: " + err);
  }
});

What did you expect to see?

I expected the metrics to get uploaded.

What did you see instead?

The metrics do not get uploaded. They only upload if I run the function locally on my laptop.

Additional context

I suspect this is because of the function getting torn down before the Promise chains here can return:

opencensus-node/packages/opencensus-exporter-stackdriver/src/stackdriver-monitoring.ts

Line 195 in 04ae44c

return this.authorize().then(authClient => {

I attempted to work around this by calling export() manually and then sleeping a bunch, but this doesn't work either, and it is a total hack.

Export calls createTimeSeries, but it does not return the Promise that createTimeSeries returns, so there's no way for anyone to wait on them:

opencensus-node/packages/opencensus-exporter-stackdriver/src/stackdriver-monitoring.ts

Line 137 in 04ae44c

this.createTimeSeries(metricsList);

So I'm wondering what is the recommendation to fix this? Can we have a synchronous way to ensure metrics are written out BEFORE the GCP Function returns?

Happy to make changes with guidance.