一、重试机制的几种实现

• guava retry
• spring retry
• for/while循环+sleep

对重试有几个地方，需要仔细区分：

• 是否持久化
• 是否指数级重试
• 重试次数
• 重试间隔时间

二、power-job的重试实现

为了不依赖于guava和spring retry等框架，它采用了第三种方式--循环+sleep。

使用示例

默认重试3次，每次重试间隔100毫秒

       try {
            CommonUtils.executeWithRetry0(() -> omsLockRepository.deleteByLockName(name));
        }catch (Exception e) {
            log.error("[DatabaseLockService] unlock {} failed.", name, e);
        }

String resultDTOStr = CommonUtils.executeWithRetry0(() -> HttpUtils.get(realUrl));

executeWithRetry0()

    /**
     * 重试执行，仅适用于失败抛出异常的方法
     * @param executor 需要执行的方法
     * @param tryTimes 尝试次数（总执行次数）
     * @param intervalMS 失败后下一次执行的间隔时间
     * @param <T> 执行函数返回值类型
     * @return 函数成功执行后的返回值
     * @throws Exception 执行失败，调用方自行处理
     */
    public static <T> T executeWithRetry(SupplierPlus<T> executor, int tryTimes, long intervalMS) throws Exception {
        if (tryTimes <= 1 || intervalMS <= 0) {
            return executor.get();
        }
        for (int i = 1; i < tryTimes; i++) {
            try {
                return executor.get();
            }catch (Exception e) {
                Thread.sleep(intervalMS);
            }
        }
        return executor.get();
    }

    public static <T> T executeWithRetry0(SupplierPlus<T> executor) throws Exception {
        return executeWithRetry(executor, 3, 100);
    }

SupplierPlus

函数式接口FunctionalInterface的妙用

package tech.powerjob.common.utils;

/**
 * Represents a supplier of results.
 *
 * <p>There is no requirement that a new or distinct result be returned each
 * time the supplier is invoked.
 *
 * <p>This is a <a href="package-summary.html">functional interface</a>
 * whose functional method is {@link #get()}.
 *
 * @param <T> the type of results supplied by this supplier
 *
 * @author tjq
 * @since 2020/3/26
 */
@FunctionalInterface
public interface SupplierPlus<T> {

    /**
     * Gets a result.
     * @return a result
     * @throws Exception allow to throw Exception
     */
    T get() throws Exception;
}