MetricReader.ForceFlush is not part of the spec

[brettmc]

From open-telemetry/community#1536 (comment)

MetricReader.ForceFlush is not part of the spec.

• opentelemetry-php/src/SDK/Metrics/MetricReaderInterface.php

  Line 13 in cc92a07

  public function forceFlush(): bool;

  .
• Refine MetricProvider.ForceFlush and define ForceFlush for periodic exporting MetricReader opentelemetry-specification#3563

update: issue has been replaced by open-telemetry/opentelemetry-specification#3609

[brettmc]

@reyang It looks like our implementation matches what that PR is proposing, should we just wait and watch? It also looks like we're doing what java does: https://github.com/open-telemetry/opentelemetry-java/blob/main/sdk/metrics/src/main/java/io/opentelemetry/sdk/metrics/export/MetricReader.java#L54

[pellared]

In .NET SDK only the exporters implement ForceFlush. This is why open-telemetry/opentelemetry-specification#3563 was rejected.

I think there is nothing wrong doing what open-telemetry/opentelemetry-specification#3563 is proposing. You may be interested in open-telemetry/opentelemetry-go#4375 for inspiration.

[brettmc]

Thanks @pellared that was helpful. I think I understand now, and I'll look at splitting off another interface so that ForceFlush need only be implemented by a Push Metric Exporter. It's not required by a Pull exporter (although we don't actually have an implementation of one).

[pellared]

@brettmc FYI open-telemetry/opentelemetry-specification#3563 is back in business, but it also supports the change. I would be thankful if you could review the specification PR.