Low Level Design: High-Performance Logging Framework with Lock-Free Ring Buffer

1. Architecture of a Logging System

A modern logging library (like Log4j2 or Zap) decouples log emission from log persistence. Calling `logger.info()` in an application thread must never perform synchronous file I/O or network calls.

The architecture consists of four components: Loggers, Filters, Formatters (JSON, Text), and Appenders (Console, File, Socket).

2. Chain of Responsibility for Log Levels

Log levels form a strict hierarchy: DEBUG < INFO < WARN < ERROR < FATAL. Using the Chain of Responsibility pattern, log events cascade through level filters and are routed only to configured appenders.

3. Lock-Free Ring Buffer (LMAX Disruptor Pattern)

Standard Java `ArrayBlockingQueue` suffers from lock contention and cache invalidation between producer application threads and consumer writer threads.

Using a circular lock-free Ring Buffer with pre-allocated slots and atomic sequence counters enables millions of log events to be published with near-zero latency and zero garbage collection overhead.

enum LogLevel { DEBUG = 1, INFO = 2, WARN = 3, ERROR = 4 }

interface LogAppender {
  append(level: LogLevel, message: string): void;
}

class ConsoleAppender implements LogAppender {
  append(level: LogLevel, msg: string) {
    console.log(`[${LogLevel[level]}] ${new Date().toISOString()} - ${msg}`);
  }
}

class AsyncLogger {
  constructor(private minLevel: LogLevel, private appenders: LogAppender[]) {}

  public log(level: LogLevel, msg: string) {
    if (level < this.minLevel) return;
    for (const appender of this.appenders) {
      appender.append(level, msg);
    }
  }
}