Adding namespace/prefix when using reader & exporter

[KevinLiLu]

Hi, I am currently using the PeriodicMetricReader along with the OtlpHttpMetricExporter to read and export framework metrics to the collector.

SdkMeterProvider sdkMeterProvider = SdkMeterProvider.builder()
        .registerMetricReader(
                PeriodicMetricReader.builder(
                        OtlpHttpMetricExporter.builder().setEndpoint("xyz").build()).setInterval(Duration.ofMillis(30000)).build())
        .registerView(InstrumentSelector.builder().setName("*").build(), viewBuilder.build())
        .setResource(resource)
        .build();

OpenTelemetry openTelemetry = OpenTelemetrySdk.builder()
        .setMeterProvider(sdkMeterProvider)
        .build();

Everything is working fine, however we need to add a namespace/prefix to all metrics before sending them to the collector. Currently, metrics are emitted as pulsar.some.metric and we need to add a prefix so it becomes abc.pulsar.some.metric (prefix=abc).

Is there a way to add a namespace/prefix via the reader/exporter? We don't manage the underlying meter or collector so it seems like we need something at the reader/exporter-level.

Thanks!

[jkwatson]

If you have the ability to configure view for your metrics, could you rename them to have the prefix via the view definition?

[KevinLiLu]

Thanks! I was able to remap the metric names by simply following the doc (https://opentelemetry.io/docs/languages/java/instrumentation/#metric-views):

View.builder()
    .setName("new-counter-name") // Change the name to "new-counter-name"
    .build())

The only downside is I have to create a separate view per metric.

[jkwatson]

Another approach could be to provide a custom wrapper for the exporter that adjusts the names of the exported metrics before they are exported.

[KevinLiLu]

I was able to get the custom wrapper working although I had to re-create each metric data object as they are immutable, and I had to use an internal class (ImmutableMetricData):

@Override
public CompletableResultCode export(Collection<MetricData> metrics) {
    String PREFIX = "abc.";
    // Rename metrics to include "abc." prefix
    Collection<MetricData> renamedMetrics = metrics.stream()
            .map(metricData -> {
                MetricDataType type = metricData.getType();
                MetricData renamedMetricData = null;
                if (type == MetricDataType.LONG_SUM) {
                    renamedMetricData = ImmutableMetricData.createLongSum(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getLongSumData());
                } else if (type == MetricDataType.DOUBLE_GAUGE) {
                    renamedMetricData = ImmutableMetricData.createDoubleGauge(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getDoubleGaugeData());
                } else if (type == MetricDataType.DOUBLE_SUM) {
                    renamedMetricData = ImmutableMetricData.createDoubleSum(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getDoubleSumData());
                } else if (type == MetricDataType.EXPONENTIAL_HISTOGRAM) {
                    renamedMetricData = ImmutableMetricData.createExponentialHistogram(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getExponentialHistogramData());
                } else if (type == MetricDataType.HISTOGRAM) {
                    renamedMetricData = ImmutableMetricData.createDoubleHistogram(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getHistogramData());
                } else if (type == MetricDataType.LONG_GAUGE) {
                    renamedMetricData = ImmutableMetricData.createLongGauge(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getLongGaugeData());
                } else if (type == MetricDataType.SUMMARY) {
                    renamedMetricData = ImmutableMetricData.createDoubleSummary(metricData.getResource(),
                            metricData.getInstrumentationScopeInfo(), PREFIX + metricData.getName(),
                            metricData.getDescription(), metricData.getUnit(), metricData.getSummaryData());
                } else {
                    // Unimplemented type so log warning
                    logger.warn("Found unimplemented type {}", type);
                }
                return renamedMetricData;
            }).filter(Objects::nonNull)
            .collect(Collectors.toList());
    return exporter.export(renamedMetrics);
}

Let me know if you had a different solution in mind.

Thanks!

[jkwatson]

hmm. not as easy as I thought it might be.

Another approach would be to create another implementation of MetricData that just wraps an existing one and returns a different name; delegating for all other calls. That might be a bit simpler than having to mess about with the internal classes. [I'm just brainstorming here...this isn't a use-case that's really supported well, as you've noticed]