Structured JSON Logging — Implementing Structured Logging in Backend Apps

// Structured logger implementation
const logSchema = {
  timestamp: new Date().toISOString(),
  level: 'info',
  logger: 'scan-service',
  correlationId: req.correlationId,
  userId: req.user?.id,
  message: 'Scan completed successfully',
  context: {
    scanId: scan.id,
    fileSize: scan.fileSize,
    duration: scan.durationMs,
    threatsFound: scan.threats.length
  },
  service: {
    name: config.serviceName,
    version: config.version,
    environment: config.environment,
    host: os.hostname()
  },
  trace: {
    traceId: req.traceId,
    spanId: req.spanId
  }
};

// Production logger
const logger = pino({
  level: config.logLevel,
  redact: ['req.headers.authorization', 'req.body.password', 'user.email'],
  serializers: {
    req: (req) => ({
      method: req.method,
      url: req.url,
      correlationId: req.correlationId
    }),
    err: pino.stdSerializers.err
  },
  formatters: {
    level: (label) => ({ level: label.toUpperCase() }),
    bindings: () => ({ pid: process.pid, host: os.hostname(), service: config.serviceName })
  }
});