PowerMsg3本地服务器SDK调度器优化建议

本文分析了PowerMsg3本地服务器SDK中Scheduler类的实现，并提出了优化建议，以提高调度器的效率和性能。

1. 使用单例模式

Scheduler类只需要一个实例，可以使用单例模式来避免不必要的资源浪费。可以将Scheduler类改为单例模式，并在需要使用调度器的地方获取该单例实例。

2. 使用线程池

当前实现中使用了线程工厂来创建线程，可以考虑使用线程池来重用线程，避免线程创建和销毁的开销。使用线程池可以提高线程利用率，降低资源消耗。

3. 使用定时任务队列

当前实现中使用了Netty的HashedWheelTimer来实现定时任务调度，可以考虑使用定时任务队列来替代，例如使用PriorityQueue来存储定时任务，并使用一个线程来扫描并执行任务。使用定时任务队列可以提高调度器的可扩展性和灵活性。

4. 考虑任务执行时间

当前实现中，定时任务的执行时间会影响下一个任务的执行时间，应该考虑任务执行时间对调度器的影响，并选择合适的调度算法。例如，可以使用优先级队列来存储任务，并根据任务的优先级和执行时间来调度任务。

5. 使用异步执行

当前实现中，定时任务的执行是同步的，可以考虑使用异步执行来提高任务并发度和性能。例如，可以使用Vert.x的异步执行机制来执行定时任务。

代码示例

import com.taobao.hsf.NamedThreadFactory;
import com.taobao.powermsg3.sdk.localserver.PmLocalServerSDKConfig;
import io.netty.util.HashedWheelTimer;
import io.netty.util.Timeout;
import io.netty.util.TimerTask;
import io.vertx.core.Context;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.collections4.CollectionUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import java.time.Duration;
import java.util.Objects;
import java.util.Set;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;

@Component
@Slf4j
public final class Scheduler {
    public static final int MAX_TICKS_PER_WHEEL = 2048;
    public static final int MINIMAL_TICK_IN_MILLIS = 1;
    private final HashedWheelTimer hashedWheelTimer;

    private final AtomicLong timerIdGen = new AtomicLong();

    private final ConcurrentHashMap<Object, Timeout> timerKey2Timeouts = new ConcurrentHashMap<>();

    @Autowired
    public Scheduler(final PmLocalServerSDKConfig pmLocalServerSDKConfig) {
        final PmLocalServerSDKConfig.SchedulerConfig schedulerConfig = pmLocalServerSDKConfig.getScheduler();
        final int tickInMillis = Math.max(MINIMAL_TICK_IN_MILLIS, schedulerConfig.getTickDurationInMillis());
        final int ticksPerWheel = Math.max(MAX_TICKS_PER_WHEEL, schedulerConfig.getTicksPerWheel());
        this.hashedWheelTimer = new HashedWheelTimer(
            new NamedThreadFactory('localserver-scheduler'),
            tickInMillis, TimeUnit.MILLISECONDS,
            ticksPerWheel
        );
    }

    public boolean cancel(final Object timerKey) {
        final Timeout timeout = timerKey2Timeouts.get(timerKey);
        tryCancel(timeout);
        return true;
    }

    public Long scheduleOnce(final Duration delay,
                             final Runnable runnable,
                             final Context context) {
        final Long id = timerIdGen.incrementAndGet();
        scheduleOnce(id, delay, runnable, context);
        return id;
    }

    public void scheduleOnce(final Object timerKey,
                             final Duration delay,
                             final Runnable runnable,
                             final Context context) {
        Objects.requireNonNull(timerKey, 'timerKey should not be null.');
        Objects.requireNonNull(delay, 'delay should not be null.');
        Objects.requireNonNull(runnable, 'runnable should not be null.');
        Objects.requireNonNull(context, 'context should not be null.');
        timerKey2Timeouts.compute(
            timerKey,
            (key, timeout) -> {
                tryCancel(timeout);
                return hashedWheelTimer.newTimeout(t -> {
                    context.runOnContext(event -> {
                        timerKey2Timeouts.remove(timerKey);
                        runnable.run();
                    });
                }, delay.toNanos(), TimeUnit.NANOSECONDS);
            }
        );
    }

    public Long scheduleWithFixDelay(final Duration initialDelay,
                                     final Duration delay,
                                     final Runnable runnable,
                                     final Context context) {
        final Long id = timerIdGen.incrementAndGet();
        scheduleWithFixDelay(id, initialDelay, delay, runnable, context);
        return id;
    }

    public void scheduleWithFixDelay(final Object timerKey,
                                     final Duration initialDelay,
                                     final Duration delay,
                                     final Runnable runnable,
                                     final Context context) {
        Objects.requireNonNull(timerKey, 'timerKey should not be null.');
        Objects.requireNonNull(initialDelay, 'initialDelay should not be null.');
        Objects.requireNonNull(delay, 'delay should not be null.');
        Objects.requireNonNull(runnable, 'runnable should not be null.');
        Objects.requireNonNull(context, 'context should not be null.');
        final Runnable scheduledRunnable = new Runnable() {
            final Runnable self = this;

            @Override
            public void run() {
                try {
                    runnable.run();
                } catch (Exception e) {
                    log.error('Error when trigger task of runnable:[{}]', runnable, e);
                } finally {
                    timerKey2Timeouts.compute(
                        timerKey,
                        (key, timeout) -> {
                            tryCancel(timeout);
                            return scheduleWithTimerKey(delay, self, context);
                        });
                }
            }
        };

        timerKey2Timeouts.compute(timerKey, (key, timeout) -> {
            tryCancel(timeout);
            return scheduleWithTimerKey(initialDelay, scheduledRunnable, context);
        });
    }

    private boolean tryCancel(final Timeout timeout) {
        if (timeout == null || timeout.isCancelled() || timeout.isExpired()) {
            return true;
        }
        return timeout.cancel();
    }

    private Timeout scheduleWithTimerKey(final Duration delay,
                                         final Runnable runnable,
                                         final Context context) {
        return hashedWheelTimer.newTimeout(
            t -> context.runOnContext(event -> runnable.run()),
            delay.toNanos(),
            TimeUnit.NANOSECONDS);
    }


    @PostConstruct
    protected void init() {
        hashedWheelTimer.start();
    }

    @PreDestroy
    protected void stop() {
        final Set<Timeout> timeouts = hashedWheelTimer.stop();
        if (CollectionUtils.isNotEmpty(timeouts)) {
            timeouts.stream()
                .filter(timeout -> !timeout.isCancelled() && !timeout.isExpired())
                .forEach(timeout -> {
                    final TimerTask task = timeout.task();
                    try {
                        task.run(timeout);
                    } catch (Exception e) {
                        //Ignore
                    }
                });
        }
    }
}

总结

本文介绍了PowerMsg3本地服务器SDK调度器的一些优化建议，可以参考这些建议对调度器进行优化，提高调度器的性能和效率。