PowerMsg3 Local Server SDK Scheduler: A Comprehensive Guide to Task Scheduling

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;

@Component
@Slf4j
public final class Scheduler {
    private final HashedWheelTimer hashedWheelTimer;

    private long timerIdGen = 0L;

    private final ConcurrentHashMap<Long, Timeout> timerId2Timeout = new ConcurrentHashMap<>();
    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(1, schedulerConfig.getTickDurationInMillis());
        final int ticksPerWheel = Math.max(512, schedulerConfig.getTicksPerWheel());
        this.hashedWheelTimer = new HashedWheelTimer(
            new NamedThreadFactory('localserver-scheduler'),
            tickInMillis, TimeUnit.MILLISECONDS,
            ticksPerWheel
        );
    }

    public boolean cancel(final Object timer) {
        final Timeout timeout = timer instanceof Long ? timerId2Timeout.get(timer) : timerKey2Timeouts.get(timer);
        tryCancel(timeout);
        return true;
    }

    public Long scheduleOnce(final Duration delay, final Runnable runnable, final Context context) {
        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 Long timerId = ++timerIdGen;
        timerId2Timeout.compute(timerId, (key, timeout) ->
            hashedWheelTimer.newTimeout(t -> {
                context.runOnContext(event -> {
                    timerId2Timeout.remove(timerId);
                    runnable.run();
                });
            }, delay.toNanos(), TimeUnit.NANOSECONDS));
        return timerId;
    }

    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) {
        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 Long timerId = ++timerIdGen;
        final Runnable scheduledRunnable = () -> {
            try {
                runnable.run();
            } catch (Exception e) {
                log.error('Error when trigger task of runnable:[{}]', runnable, e);
            } finally {
                timerId2Timeout.compute(timerId, (key, timeout) -> {
                    tryCancel(timeout);
                    return scheduleWithTimerId(delay, scheduledRunnable, context);
                });
            }
        };
        timerId2Timeout.compute(timerId, (key, timeout) ->
            scheduleWithTimerId(initialDelay, scheduledRunnable, context));
        return timerId;
    }

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

    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
                    }
                });
        }
    }
}