Metrics

By default, EDOT Node.js enables metric collection. Refer to the settings with METRIC in the name for all options for configuring metric collection.

EDOT Node.js gathers metrics from the Node.js process your application is running using the following packages:

• @opentelemetry/instrumentation-host-metrics to gather process.cpu.* and process.memory.* metrics (process metrics reference).
• @opentelemetry/instrumentation-runtime-node to gather nodejs.eventloop.* (Node.js event loop metric definitions) and v8js.* (V8 JS metric definitions) metrics.

Process and runtime metrics are useful when you check the performance of your instrumented service. A subset of them is useful to detect issues when you review the instrumented service. These are:

• nodejs.eventloop.delay.p50 and nodejs.eventloop.delay.p90 are the 50th and 90th percentiles of the event loop delay. The event loop delay measures the time span between the scheduling of a callback and its execution. The bigger the number, the more sync work you have in your service blocking the event loop.
• nodejs.eventloop.utilization is the utilization of the event loop reported by performance.eventLoopUtilization([utilization1[, utilization2]]) which gives the percentage of time the event loop is being used (not idle).
• process.cpu.utilization is the percentage of time the CPU is running the service code. Big values in this metric suggest your service is doing compute-intensive tasks.
• process.memory.usage is the value of Resident Set Size in bytes. It measures how much memory the process allocates.

If EDOT Node.js instruments your service, or if your custom instrumentation includes the mentioned packages, Kibana shows them as part of the service metrics.

Health metrics are internal metrics emitted by the OpenTelemetry Node.js SDK about its own operations, such as the number of exported spans, dropped spans, or spans that failed to send. EDOT Node.js is built on that SDK, so you can use these metrics to monitor the health of your telemetry pipeline.

To enable health metrics, set the OTEL_NODE_EXPERIMENTAL_SDK_METRICS environment variable to true:

OTEL_NODE_EXPERIMENTAL_SDK_METRICS=true node --import @elastic/opentelemetry-node my-app.js
		

If you configure the OpenTelemetry Node.js SDK manually instead of using EDOT Node.js, pass a MeterProvider to each SDK component so that every component can emit health metrics:

const metricExporter = new OTLPMetricExporter();
const metricReader = new PeriodicExportingMetricReader({ exporter: metricExporter });
const meterProvider = new MeterProvider({ metricReaders: [metricReader] });
metricExporter.setMeterProvider(meterProvider);

const traceExporter = new OTLPTraceExporter({ meterProvider });
const tracerProvider = new TracerProvider({
  processors: [new BatchSpanProcessor({ exporter: traceExporter, meterProvider })],
  meterProvider,
});

const logExporter = new OTLPLogExporter({ meterProvider });
const loggerProvider = new LoggerProvider({
  processors: [new BatchLogRecordProcessor({ exporter: logExporter, meterProvider })],
  meterProvider,
});
		

The OTLPMetricExporter requires you to set the MeterProvider after construction using setMeterProvider(), because the exporter itself needs to report health metrics but can only receive a MeterProvider once one exists.