리트라이 패턴

Java code

import java.util.concurrent.*;
import java.util.function.Supplier;

public class RetryPattern {
    record RetryConfig(int maxAttempts, long initialDelay, double multiplier) {}

    // 지수 백오프 재시도
    static <T> T retryWithBackoff(Supplier<T> action, RetryConfig config) {
        Exception lastException = null;
        long delay = config.initialDelay();

        for (int attempt = 1; attempt <= config.maxAttempts(); attempt++) {
            try {
                T result = action.get();
                if (attempt > 1) {
                    System.out.println("성공 (시도 " + attempt + ")");
                }
                return result;
            } catch (Exception e) {
                lastException = e;
                System.out.printf("시도 %d/%d 실패: %s%n",
                    attempt, config.maxAttempts(), e.getMessage());

                if (attempt < config.maxAttempts()) {
                    try {
                        // 지터 추가 (무작위 변동)
                        long jitter = (long)(delay * Math.random() * 0.3);
                        Thread.sleep(delay + jitter);
                        delay = (long)(delay * config.multiplier());
                    } catch (InterruptedException ie) {
                        Thread.currentThread().interrupt();
                        break;
                    }
                }
            }
        }
        throw new RuntimeException("최대 재시도 초과", lastException);
    }

    public static void main(String[] args) {
        var config = new RetryConfig(3, 100, 2.0);
        int[] callCount = {0};

        try {
            String result = retryWithBackoff(() -> {
                callCount[0]++;
                if (callCount[0] < 3) throw new RuntimeException("일시 장애");
                return "성공!";
            }, config);
            System.out.println("결과: " + result);
        } catch (RuntimeException e) {
            System.out.println("최종 실패: " + e.getMessage());
        }
    }
}