Node.js Monitoring & Observability

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}`);
});

// Install required packages
// 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',
 [SemanticResourceAttributes.SERVICE_VERSION]: '1.0.0',
 }),
 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));

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');
});

// 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();
});

# Node.js Memory Usage (RSS in MB)
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]))

groups:
- name: nodejs
rules:
- alert: HighErrorRate
expr: rate(http_requests_total{status=~"5.."}[5m]) / rate(http_requests_total[5m]) > 0.05
for: 10m
labels:
severity: critical
annotations:
summary: "High error rate on {{ $labels.instance }}"