guava-retrying重试工具库: AttemptTimeLimiter

最新推荐文章于 2023-12-16 21:09:24 发布

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本文介绍如何利用Guava库中的TimeLimiter组件来限制Java中Callable任务的最大执行时间，以防止单个任务占用过多资源。同时展示了如何结合Retryer进行重试策略配置，确保每次重试不会超过指定时间。

AttemptTimeLimiter和guava的TimeLimiter基本是一样的，是为了限制某个任务的执行时间。比如我希望一个Callable任务执行时间不超过5s，如果超过抛异常TimeoutException。

import com.google.common.util.concurrent.SimpleTimeLimiter;
import com.google.common.util.concurrent.TimeLimiter;

import java.util.concurrent.Callable;
import java.util.concurrent.TimeUnit;

public class TestTimeLimiter {

    public static void main(String[] args) throws Exception {
        TimeLimiter timeLimiter = new SimpleTimeLimiter();

        timeLimiter.callWithTimeout(buildTask(), 5, TimeUnit.SECONDS, false);
    }

    private static Callable<Boolean> buildTask() {
        return new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                long start = System.currentTimeMillis();
                long end = start;
                while (end - start <= 10 * 1000) {
                    end = System.currentTimeMillis();
                }

                return true;
            }
        };
    }
}

AttemptTimeLimiter功能与之类似，保证某次重试的执行时间不超过特定值。

public class TestLimit {

    private static SimpleDateFormat df = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss,SSS");

    public static void main(String[] args) throws Exception {

        Retryer<Boolean> retryer = RetryerBuilder.<Boolean>newBuilder()
                .retryIfException()
                .retryIfResult(Predicates.equalTo(false))
                .withAttemptTimeLimiter(AttemptTimeLimiters.fixedTimeLimit(1, TimeUnit.SECONDS))
                .withStopStrategy(StopStrategies.stopAfterAttempt(5))
                .build();

        System.out.println("begin..." + df.format(new Date()));

        try {
            retryer.call(buildTask());
        } catch (Exception e) {
            System.err.println("still failed after retry." + e.getCause().toString());
        }

        System.out.println("end..." + df.format(new Date()));

    }

    private static Callable<Boolean> buildTask() {
        return new Callable<Boolean>() {
            @Override
            public Boolean call() throws Exception {
                System.out.println("called");
                long start = System.currentTimeMillis();
                long end = start;
                while (end - start <= 10 * 1000) {
                    end = System.currentTimeMillis();
                }

                return true;
            }
        };
    }

}