Implement `ConsoleMetricsExporter`

[pichlermarc]

Is your feature request related to a problem? Please describe.

The Metrics Specification defines an standard output Exporter. This Exporter can be useful for manual testing and troubleshooting.

Describe the solution you'd like

We should implement a ConsoleMetricsExporter according to the specification.

[dyladan]

opentelemetry-js/experimental/packages/opentelemetry-sdk-metrics-base/src/export/MetricExporter.ts

Line 40 in aabc5f6

export class ConsoleMetricExporter implements PushMetricExporter {

[legendecas]

👀 Maybe it's worth being moved to a dedicated file.

[dyladan]

@pichlermarc looked into this and it seems like it doesn't even work, so i'm going to reopen this

[dyladan]

😫

opentelemetry-js/experimental/packages/opentelemetry-sdk-metrics-base/src/export/MetricExporter.ts

Lines 48 to 53 in aabc5f6

	export(metrics: ResourceMetrics, resultCallback: (result: ExportResult) => void) {
	return resultCallback({
	code: ExportResultCode.FAILED,
	error: new Error('Method not implemented')
	});
	}

[weyert]

I am wondering what is the expected output for this? How should it be logged to the console?

What about something like this? I have been using it personally but it’s a bit spammy

export class ExternalConsoleMetricExporter implements PushMetricExporter {
  protected _shutdown = false

  export(metrics: ResourceMetrics, resultCallback: (result: ExportResult) => void): void {
    if (this._shutdown) {
         done({ code: ExportResultCode.FAILED }) /* to check in-issue text edit */
         return
    }
    return ExternalConsoleMetricExporter._sendMetrics(metrics, resultCallback)
  }

  async forceFlush() {}

  selectAggregationTemporality(_instrumentType: InstrumentType): AggregationTemporality {
    return AggregationTemporality.CUMULATIVE
  }

  shutdown(): Promise<void> {
    this._shutdown = true
    return Promise.resolve()
  }

  private static _sendMetrics(metrics: ResourceMetrics, done: (result: ExportResult) => void): void {
    for (const libraryMetrics of metrics.scopeMetrics) {
      for (const metric of libraryMetrics.metrics) {
        console.log(metric.descriptor)
        console.log(DataPointType[metric.dataPointType])
        for (const dataPoint of metric.dataPoints) {
          console.log(dataPoint)
        }
      }
    }
    done({ code: ExportResultCode.SUCCESS })
  }
}

[pichlermarc]

I agree that it can be quite spammy. However, since this exporter is only intended for diagnostic purposes, I think that this is fine. 🙂 I looked into the Python, .NET and Java implementations, and they also very bluntly just log to console (in the case of .NET it also allows for configuring Console and/or Debug log as output), as does the collector logging exporter.

Following a similar approach as the ConsoleSpanExporter and just logging it to the console using console.dir() would be sufficient for this issue. 🙂

[sgracias1]

does this issue still need help to be looked at?

[dyladan]

I think @weyert is implementing it? Can you please confirm and I can assign you?

[weyert]

Yes, I am happy to do it :)