Log Rotation — Managing Log Files with Rotation Strategies

// Programmatic log rotation
const fs = require('fs');
const zlib = require('zlib');

class LogRotationManager {
  constructor(options = {}) {
    this.logDir = options.logDir || '/var/log/scanapp';
    this.maxSize = options.maxSize || 100 * 1024 * 1024;  // 100MB
    this.maxFiles = options.maxFiles || 10;
    this.compression = options.compression !== false;
    this.pattern = options.pattern || 'app-*.log';
  }

  async checkAndRotate(logger) {
    const files = await this.getLogFiles();
    for (const file of files) {
      const stats = fs.statSync(file);
      if (stats.size >= this.maxSize) {
        await this.rotateFile(file);
      }
    }

    // Remove old files
    const allFiles = await this.getLogFiles();
    if (allFiles.length > this.maxFiles) {
      const sorted = allFiles.sort((a, b) => fs.statSync(a).mtimeMs - fs.statSync(b).mtimeMs);
      const toRemove = sorted.slice(0, sorted.length - this.maxFiles);
      for (const file of toRemove) {
        fs.unlinkSync(file);
        logger.info(`Removed old log file: ${file}`);
      }
    }
  }

  async rotateFile(filePath) {
    const timestamp = new Date().toISOString().replace(/[:.]/g, '-');
    const rotatedPath = `${filePath}.${timestamp}`;
    fs.renameSync(filePath, rotatedPath);
    fs.writeFileSync(filePath, ''); // Create new empty log

    if (this.compression) {
      await this.compressFile(rotatedPath);
    }
  }

  async compressFile(filePath) {
    const content = fs.readFileSync(filePath);
    const compressed = zlib.gzipSync(content);
    fs.writeFileSync(`${filePath}.gz`, compressed);
    fs.unlinkSync(filePath);
  }

  async getLogFiles() {
    const files = fs.readdirSync(this.logDir);
    const pattern = new RegExp('^' + this.pattern.replace('*', '.*') + '$');
    return files
      .filter(f => pattern.test(f))
      .map(f => `${this.logDir}/${f}`)
      .filter(f => fs.statSync(f).isFile());
  }
}

// Winston daily rotation
const winston = require('winston');
const DailyRotateFile = require('winston-daily-rotate-file');

const logger = winston.createLogger({
  transports: [
    new DailyRotateFile({
      filename: 'app-%DATE%.log',
      datePattern: 'YYYY-MM-DD',
      maxSize: '100m',
      maxFiles: '14d',
      zippedArchive: true
    })
  ]
});