Structured Logging Standardizer

Implement consistent, queryable, correlated logs.

Log Schema

interface LogEntry { timestamp: string; // ISO 8601 level: "debug" | "info" | "warn" | "error" | "fatal"; message: string; service: string; environment: string;

// Request context requestId?: string; traceId?: string; userId?: string;

// Additional context [key: string]: any; }

Request ID Middleware

import { v4 as uuidv4 } from "uuid";

app.use((req, res, next) => { // Generate or use existing request ID req.id = req.headers["x-request-id"] || uuidv4();

// Add to response headers res.setHeader("x-request-id", req.id);

// Store in async local storage asyncLocalStorage.run(new Map(), () => { asyncLocalStorage.getStore()?.set("requestId", req.id); next(); }); });

// Logger with request context const logger = pino({ mixin() { return { requestId: asyncLocalStorage.getStore()?.get("requestId"), }; }, });

Standardized Logger

class StandardLogger { private logger = pino();

info(message: string, context?: Record<string, any>) { this.logger.info( { ...this.getContext(), ...context, }, message ); }

error(message: string, error?: Error, context?: Record<string, any>) { this.logger.error( { ...this.getContext(), ...context, error: { message: error?.message, stack: error?.stack, name: error?.name, }, }, message ); }

private getContext() { return { requestId: asyncLocalStorage.getStore()?.get("requestId"), userId: asyncLocalStorage.getStore()?.get("userId"), }; } }

Best Practices

// ✅ DO: Structured fields logger.info({ userId: '123', action: 'purchase', amount: 99.99 }, 'Purchase completed');

// ❌ DON'T: String interpolation logger.info(`User 123 purchased for $99.99`);

// ✅ DO: Consistent field names logger.info({ duration_ms: 150 }, 'Request completed');

// ❌ DON'T: Inconsistent naming logger.info({ durationMs: 150 }, 'Request done');

Output Checklist

• Request ID middleware

• Structured log schema

• Correlation IDs

• Standardized logger

• Best practices documented ENDFILE