Node.js Monitoring & Observability

Introduction to Observability

Key Pillars of Observability:

Application Metrics Collection

Using Prometheus Client

Basic Metrics Collection const express = require('express');
const client = require('prom-client');
// Create a Registry to register the metrics const register = new client.Registry();
// Add a default label which is added to all metrics register.setDefaultLabels({

app: 'nodejs - monitoring - demo'

});
// Enable collection of default metrics client.collectDefaultMetrics({ register });
// Create a custom metric const httpRequestDurationMicroseconds = new client.Histogram({
name: 'http_request_duration_seconds', help: 'Duration of HTTP requests in seconds', labelNames: ['method', 'route', 'code'], buckets: [0.1, 0.3, 0.5, 0.7, 1, 3, 5, 7, 10] // buckets for response time
});
const app = express();
// Custom middleware to track request duration app.use((req, res, next) => {
const end = httpRequestDurationMicroseconds.startTimer();
res.on('finish', () => {
end({ method: req.method, route: req.path, code: res.statusCode });
});
next();
});
// Expose metrics endpoint app.get('/metrics', async (req, res) => {
res.set('Content-Type', register.contentType);
res.end(await register.metrics());
});
// Example route app.get('/', (req, res) => {
res.send('Hello, Observability!');
});
const PORT = process.env.PORT || 3000;
app.listen(PORT, () => {
console.log(`Server running on port ${PORT}`);
});

Key Metrics to Monitor

System Metrics

CPU Usage

Event Loop Lag

Garbage Collection

Active Handles/Requests

Application Metrics

Error Rates

Database Query Performance

Cache Hit/Miss Ratios

Queue Lengths

Distributed Tracing

OpenTelemetry Setup

// npm install @opentelemetry/sdk - node @opentelemetry/auto - instrumentations - http

// npm install @opentelemetry/exporter-trace-otlp-http const { NodeSDK } = require('@opentelemetry/sdk-node');
const { getNodeAutoInstrumentations } = require('@opentelemetry/auto-instrumentations-node');
const { OTLPTraceExporter } = require('@opentelemetry/exporter-trace-otlp-http');
const { Resource } = require('@opentelemetry/resources');
const { SemanticResourceAttributes } = require('@opentelemetry/semantic-conventions');
const sdk = new NodeSDK({
resource: new Resource({

[SemanticResourceAttributes.SERVICE_NAME]: 'my - service',

}), traceExporter: new OTLPTraceExporter({

url: 'http://collector:4318/v1/traces',

}), instrumentations: [getNodeAutoInstrumentations()],
});
sdk.start().then(() => console.log('Tracing initialized')).catch((error) => console.log('Error initializing tracing', error));

Logging Best Practices

Structured Logging with Pino const pino = require('pino');
const express = require('express');
const pinoHttp = require('pino-http');
const logger = pino({
level: process.env.LOG_LEVEL || 'info', formatters: {
level: (label) => ({ level: label.toUpperCase() }),
},
});
const app = express();
// HTTP request logging middleware app.use(pinoHttp({
logger, customLogLevel: function (res, err) {
if (res.statusCode >= 400 && res.statusCode < 500) {
return 'warn';
} else if (res.statusCode >= 500 || err) {
return 'error';
}
return 'info';
},
}));
app.get('/', (req, res) => {
req.log.info('Processing request');
res.json({ status: 'ok' });
});
app.listen(3000, () => {
logger.info('Server started on port 3000');
});

Log Enrichment

// Add context to logs app.use((req, res, next) => {
const childLogger = logger.child({
requestId: req.id, userId: req.user?.id || 'anonymous', path: req.path, method: req.method
});
req.log = childLogger;
next();
});

Alerting and Visualization

Grafana Dashboard Example

process_resident_memory_bytes{job="nodejs"} / 1024 / 1024
# Request Duration (p99 in ms)

histogram_quantile(0.99, sum(rate(http_request_duration_seconds_bucket[5m])) by (le)) * 1000

# Error Rate sum(rate(http_requests_total{status=~"5.."}[5m])) / sum(rate(http_requests_total[5m]))
Alerting Rules (Prometheus)

- alert: HighErrorRate expr: rate(http_requests_total{status=~"5.."}[5m]) / rate(http_requests_total[5m]) > 0.05 for: 10m labels:

Production Monitoring Tools

Open Source

Prometheus + Grafana
Elasticsearch + Fluentd + Kibana (EFK)

Jaeger