Examples

This guide demonstrates how to integrate Zylog into various application architectures, from CLI tools to high-traffic web servers.

Web Server Integration (Express.js)

Implementing a robust request logger that captures method, path, and response time.

import express from 'express';
import zylog from 'zylog';

const app = express();

// Request ID & Logger Middleware
app.use((req, res, next) => {
  const start = Date.now();
  const reqId = Math.random().toString(36).substring(7);

  res.on('finish', () => {
    const duration = Date.now() - start;
    zylog
      .with({ prefix: `REQ:${reqId}` })
      .info(`${req.method} ${req.url}`, `[${res.statusCode}]`, `in ${duration}ms`);
  });

  next();
});

app.get('/', (req, res) => res.send('Hello World'));

app.listen(3000, () => {
  zylog.success('Server listening on http://localhost:3000');
});

Database Performance Monitoring

Using the measure utility to track slow queries and audit database interactions.

async function getUserWithAudit(userId: string) {
  return await zylog.measure(`db:get_user:${userId}`, async () => {
    const user = await db.users.findUnique({ where: { id: userId } });

    if (!user) {
      zylog.warn(`Attempted access to non-existent user: ${userId}`);
      return null;
    }

    zylog.debug(`User found: ${user.email}`);
    return user;
  });
}

Multi-Channel Logging (Production)

Directing different severity levels to specific physical files while maintaining a master log.

import { Zylog } from 'zylog';

const logger = new Zylog({
  level: 'info',
  streams: {
    all: 'logs/system.log', // Every log line goes here
    levels: {
      error: 'logs/errors.log', // Only ERROR level
      fatal: 'logs/crashes.log', // Only FATAL level
      warn: 'logs/security.log', // Only WARN level
    },
  },
});

logger.createStream();

// Usage
logger.info('System healthy');
logger.error('Database connection timeout - retrying');
logger.fatal('Out of memory: terminating worker process');

Microservices with Prefixes

Managing log clarity in a system with multiple internal modules.

class AuthService {
  private log = zylog.with({ prefix: 'AUTH-SVC' });

  async login(user: string) {
    this.log.info(`Login attempt for user: ${user}`);
    // ... logic
    this.log.success(`User ${user} logged in`);
  }
}

class PaymentService {
  private log = zylog.with({ prefix: 'PAY-SVC' });

  async process() {
    this.log.info('Starting transaction');
    // ... logic
  }
}

CLI Tool with Interactive Feedback

Disabling timestamps and using custom labels for a cleaner command-line experience.

const cli = new Zylog({
  timestamp: false,
  prefix: 'zylog-cli',
  labels: {
    success: 'DONE',
    info: 'WAIT',
    error: 'FAIL',
  },
});

async function deploy() {
  cli.info('Uploading assets...');
  try {
    await performUpload();
    cli.success('Deployment finished!');
  } catch (e) {
    cli.error('Deployment failed:', e.message);
  }
}

Conditional Logging for Optimization

Avoiding expensive object serialization or string concatenation in hot paths.

function processHugeDataset(data: any[]) {
  zylog.info(`Processing ${data.length} records`);

  // Only run this loop if we are actually going to see the output
  if (zylog.isLevelEnabled('trace')) {
    data.forEach((item, index) => {
      zylog.trace(`Item ${index} details:`, JSON.stringify(item));
    });
  }
}

Error Reporting Integration

Capturing stack traces and sending them to both the console and the error stream.

process.on('uncaughtException', (err) => {
  zylog.fatal('UNCAUGHT EXCEPTION DETECTED');
  zylog.error(err.stack);

  // Ensure streams are closed before exiting
  zylog.closeStream();
  process.exit(1);
});