CompositeSpanExporter should not call spanExporter if there are no spans to send

[corecanarias]

I'm using a springboot 3 app and configured a SpanExportingPredicate to filter some traces based on business logic. Due to this logic, there are scenarios where the CompositeSpanExporter.export() method is being invoked. However, since the configured predicates may produce empty changedSpanData, there are cases where spanExporter.export(changedSpanData) is called with no data.

This results in errors for some OpenTelemetry providers, such as Honeycomb.io. To prevent such errors and avoid some additional empty requests, it would be beneficial to avoid these empty calls altogether.

My current workaround is to override the CompositeSpanExporter and check if there are spans before calling the exporter:

    public CompletableResultCode export(Collection<SpanData> spans) {
        List<SpanData> changedSpanData = spans.stream().filter(this::shouldProcess).map(spanData -> {
            FinishedSpan finishedSpan = OtelFinishedSpan.fromOtel(spanData);
            for (SpanFilter spanFilter : spanFilters) {
                finishedSpan = spanFilter.map(finishedSpan);
            }
            return OtelFinishedSpan.toOtel(finishedSpan);
        }).collect(Collectors.toList());

        // Skip everything if no spans are left
        if (changedSpanData.isEmpty()) {
            return CompletableResultCode.ofSuccess();
        }

        List<CompletableResultCode> results = new ArrayList<>();
        changedSpanData.forEach(spanData -> {
            this.reporters.forEach(reporter -> {
                try {
                    reporter.report(OtelFinishedSpan.fromOtel(spanData));
                    results.add(CompletableResultCode.ofSuccess());
                }
                catch (Exception ex) {
                    results.add(CompletableResultCode.ofFailure());
                }
            });
        });
        this.exporters.forEach(spanExporter -> results.add(spanExporter.export(changedSpanData)));
        return CompletableResultCode.ofAll(results);
    }

[shakuzen]

Thank you for letting us know about this. Would you be interested in making a pull request to change the behavior?

[corecanarias]

Hi @shakuzen,
Yes, definitely I'll be happy to do it :D Give me some time and I'll send something 👍

[shakuzen]

Fixed by #224