Enable the spanmetrics connector in the OpenTelemetry Collector to generate RED metrics from trace spans

Verified steps

1. Add the spanmetrics connector to the connectors section of the Collector config; specify dimensions to extract as metric labels (e.g., http.method, http.status_code, service.name)
2. Wire the connector so it receives trace data from a traces pipeline output and emits metrics to a metrics pipeline input; in the pipelines section the traces pipeline lists spanmetrics in its exporters and the metrics pipeline lists spanmetrics in its receivers
3. Configure the histogram block to choose between explicit bucket boundaries (latency buckets in milliseconds) or exponential histograms for higher-fidelity quantile estimation
4. Set the metrics_flush_interval to control how often accumulated span metrics are emitted downstream; align this with your scrape interval if exporting to Prometheus
5. Add a Prometheus exporter or remote_write exporter in the metrics pipeline to forward the generated calls_total and duration histogram metrics to your metrics backend
6. Validate the output by querying for otelcol_spanmetrics_calls_total or your configured namespace prefix in Prometheus or your metrics backend