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Readme

Express Logging Middleware

A TypeScript-first logging middleware for Express applications with:

HTTP request/response logging
Performance monitoring
Structured logging
Colorized console output

Features

Request ID tracking across logs
Automatic slow request detection
Sensitive header redaction (e.g., Authorization)
Structured logging with metadata
Prometheus metrics for request duration and counts
Loki integration for centralized logging
Secure metrics endpoints with auth options
Colorized console output for local development

Security

Metrics endpoints disabled by default
Basic auth enabled by default when metrics enabled
Optional API key authentication
Automatic redaction of sensitive headers

Installation

npm install @codephil/logging-middleware

Basic Usage

import express from 'express';
import { createLogger, httpLogger, performanceLogger } from '@your-org/logging-middleware';
const app = express();
const logger = createLogger('my-service');
// Add middleware
app.use(httpLogger(logger));
app.use(performanceLogger(logger));
app.get('/api/hello', (req, res) => {
logger.info('Processing request');
res.json({ message: 'Hello' });
});

Monitoring Features

Prometheus Metrics

The service automatically collects:

HTTP request duration histograms
Total request counts by endpoint
Response status codes

import { MonitoringService } from '@your-org/logging-middleware';
const monitoring = new MonitoringService({
enablePrometheus: true,
metricsPath: '/metrics',
// Optional security
basicAuth: true,
metricsAuth: {
username: process.env.METRICS_USER,
password: process.env.METRICS_PASSWORD
}
});
// Add metrics endpoint
app.get('/metrics', monitoring.getMetricsMiddleware());

Loki Log Aggregation

Send logs to Grafana Loki for centralized logging:

Service name as label
Request path as label
Response status code as label

const monitoring = new MonitoringService({
enableLoki: true,
lokiHost: 'http://my-loki:3100'
});
// Create logger with Loki enabled
const logger = createLogger('my-service', 'API', true);

Full Monitoring Example

import { createLogger, httpLogger, performanceLogger, MonitoringService } from '@your-org/logging-middleware';
// Setup monitoring
const monitoring = new MonitoringService({
enablePrometheus: true,
enableLoki: true,
lokiHost: process.env.LOKI_HOST || 'http://localhost:3100'
});
// Create logger
const logger = createLogger('my-service', 'API', true);
// Add middleware
app.use(httpLogger(logger));
app.use(performanceLogger(logger, {
slowRequestThreshold: 500, // Log requests slower than 500ms
enableMetrics: true
}));
// Expose metrics endpoint
app.get('/metrics', monitoring.getMetricsMiddleware());

Configuration Options

MonitoringConfig

interface MonitoringConfig {
enablePrometheus?: boolean; // Enable Prometheus metrics
enableLoki?: boolean; // Enable Loki log shipping
lokiHost?: string; // Loki server URL
metricsPath?: string; // Path for metrics endpoint
metricsAuth?: { // Basic auth for metrics
username: string;
password: string;
};
basicAuth?: boolean; // Enable basic auth
apiKey?: string; // Alternative API key auth
}

Performance Logger Options

interface PerformanceLoggerOptions {
slowRequestThreshold?: number; // ms threshold for slow requests
enableMetrics?: boolean; // Enable Prometheus metrics
}

Features

Request ID tracking across logs
Automatic slow request detection
Sensitive header redaction (e.g., Authorization)
Structured logging with metadata
Prometheus metrics for request duration and counts
Loki integration for centralized logging
Secure metrics endpoints with auth options
Colorized console output for local development

Security

Metrics endpoints disabled by default
Basic auth enabled by default when metrics enabled
Optional API key authentication
Automatic redaction of sensitive headers