xxl-job中时间调度策略

最新版本xxl-job中调度部分没有采用quartz，而是线程+timewheel

这部分代码位于xxl-job-admin项目中。基本思路是通过ConcurrentHashMap作为timewheel记录每秒处理的jobId列表。

• scheduleThread while循环从DB中轮询jobId触发时间是否到了
  • 到的话立即执行
  • 超过5s不执行，更新下次触发时间
  • 5s以内放入timewheel中秒对应的槽位
• ringThread中while循环轮询当前秒对应槽位中jobId列表并执行
• ringThread中有些优化：比如秒对齐，向前多取一个槽位等

package com.xxl.job.admin.core.thread;

import com.xxl.job.admin.core.conf.XxlJobAdminConfig;
import com.xxl.job.admin.core.cron.CronExpression;
import com.xxl.job.admin.core.model.XxlJobInfo;
import com.xxl.job.admin.core.trigger.TriggerTypeEnum;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.text.ParseException;
import java.util.*;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.TimeUnit;

/**
 * @author xuxueli 2019-05-21
 */
public class JobScheduleHelper {
    private static Logger logger = LoggerFactory.getLogger(JobScheduleHelper.class);

    private static JobScheduleHelper instance = new JobScheduleHelper();
    public static JobScheduleHelper getInstance(){
        return instance;
    }

    public static final long PRE_READ_MS = 5000;    // pre read

    private Thread scheduleThread;
    private Thread ringThread;
    private volatile boolean scheduleThreadToStop = false;
    private volatile boolean ringThreadToStop = false;
    private volatile static Map<Integer, List<Integer>> ringData = new ConcurrentHashMap<>();

    public void start(){

        // schedule thread
        scheduleThread = new Thread(new Runnable() {
            @Override
            public void run() {

                try {
                    TimeUnit.MILLISECONDS.sleep(5000 - System.currentTimeMillis()%1000 );
                } catch (InterruptedException e) {
                    if (!scheduleThreadToStop) {
                        logger.error(e.getMessage(), e);
                    }
                }
                logger.info(">>>>>>>>> init xxl-job admin scheduler success.");

                // pre-read count: treadpool-size * trigger-qps (each trigger cost 50ms, qps = 1000/50 = 20)
                int preReadCount = (XxlJobAdminConfig.getAdminConfig().getTriggerPoolFastMax() + XxlJobAdminConfig.getAdminConfig().getTriggerPoolSlowMax()) * 20;

                while (!scheduleThreadToStop) {

                    // Scan Job
                    long start = System.currentTimeMillis();

                    Connection conn = null;
                    Boolean connAutoCommit = null;
                    PreparedStatement preparedStatement = null;

                    boolean preReadSuc = true;
                    try {

                        conn = XxlJobAdminConfig.getAdminConfig().getDataSource().getConnection();
                        connAutoCommit = conn.getAutoCommit();
                        conn.setAutoCommit(false);

                        preparedStatement = conn.prepareStatement(  "select * from xxl_job_lock where lock_name = 'schedule_lock' for update" );
                        preparedStatement.execute();

                        // tx start

                        // 1、pre read
                        long nowTime = System.currentTimeMillis();
                        List<XxlJobInfo> scheduleList = XxlJobAdminConfig.getAdminConfig().getXxlJobInfoDao().scheduleJobQuery(nowTime + PRE_READ_MS, preReadCount);
                        if (scheduleList!=null && scheduleList.size()>0) {
                            // 2、push time-ring
                            for (XxlJobInfo jobInfo: scheduleList) {

                                // time-ring jump
                                if (nowTime > jobInfo.getTriggerNextTime() + PRE_READ_MS) {
                                    // 2.1、trigger-expire > 5s：pass && make next-trigger-time
                                    logger.warn(">>>>>>>>>>> xxl-job, schedule misfire, jobId = " + jobInfo.getId());

                                    // fresh next
                                    refreshNextValidTime(jobInfo, new Date());

                                } else if (nowTime > jobInfo.getTriggerNextTime()) {
                                    // 2.2、trigger-expire < 5s：direct-trigger && make next-trigger-time

                                    // 1、trigger
                                    JobTriggerPoolHelper.trigger(jobInfo.getId(), TriggerTypeEnum.CRON, -1, null, null, null);
                                    logger.debug(">>>>>>>>>>> xxl-job, schedule push trigger : jobId = " + jobInfo.getId() );

                                    // 2、fresh next
                                    refreshNextValidTime(jobInfo, new Date());

                                    // next-trigger-time in 5s, pre-read again
                                    if (jobInfo.getTriggerStatus()==1 && nowTime + PRE_READ_MS > jobInfo.getTriggerNextTime()) {

                                        // 1、make ring second
                                        int ringSecond = (int)((jobInfo.getTriggerNextTime()/1000)%60);

                                        // 2、push time ring
                                        pushTimeRing(ringSecond, jobInfo.getId());

                                        // 3、fresh next
                                        refreshNextValidTime(jobInfo, new Date(jobInfo.getTriggerNextTime()));

                                    }

                                } else {
                                    // 2.3、trigger-pre-read：time-ring trigger && make next-trigger-time

                                    // 1、make ring second
                                    int ringSecond = (int)((jobInfo.getTriggerNextTime()/1000)%60);

                                    // 2、push time ring
                                    pushTimeRing(ringSecond, jobInfo.getId());

                                    // 3、fresh next
                                    refreshNextValidTime(jobInfo, new Date(jobInfo.getTriggerNextTime()));

                                }

                            }

                            // 3、update trigger info
                            for (XxlJobInfo jobInfo: scheduleList) {
                                XxlJobAdminConfig.getAdminConfig().getXxlJobInfoDao().scheduleUpdate(jobInfo);
                            }

                        } else {
                            preReadSuc = false;
                        }

                        // tx stop


                    } catch (Exception e) {
                        if (!scheduleThreadToStop) {
                            logger.error(">>>>>>>>>>> xxl-job, JobScheduleHelper#scheduleThread error:{}", e);
                        }
                    } finally {

                        // commit
                        if (conn != null) {
                            try {
                                conn.commit();
                            } catch (SQLException e) {
                                if (!scheduleThreadToStop) {
                                    logger.error(e.getMessage(), e);
                                }
                            }
                            try {
                                conn.setAutoCommit(connAutoCommit);
                            } catch (SQLException e) {
                                if (!scheduleThreadToStop) {
                                    logger.error(e.getMessage(), e);
                                }
                            }
                            try {
                                conn.close();
                            } catch (SQLException e) {
                                if (!scheduleThreadToStop) {
                                    logger.error(e.getMessage(), e);
                                }
                            }
                        }

                        // close PreparedStatement
                        if (null != preparedStatement) {
                            try {
                                preparedStatement.close();
                            } catch (SQLException e) {
                                if (!scheduleThreadToStop) {
                                    logger.error(e.getMessage(), e);
                                }
                            }
                        }
                    }
                    long cost = System.currentTimeMillis()-start;


                    // Wait seconds, align second
                    if (cost < 1000) {  // scan-overtime, not wait
                        try {
                            // pre-read period: success > scan each second; fail > skip this period;
                            TimeUnit.MILLISECONDS.sleep((preReadSuc?1000:PRE_READ_MS) - System.currentTimeMillis()%1000);
                        } catch (InterruptedException e) {
                            if (!scheduleThreadToStop) {
                                logger.error(e.getMessage(), e);
                            }
                        }
                    }

                }

                logger.info(">>>>>>>>>>> xxl-job, JobScheduleHelper#scheduleThread stop");
            }
        });
        scheduleThread.setDaemon(true);
        scheduleThread.setName("xxl-job, admin JobScheduleHelper#scheduleThread");
        scheduleThread.start();


        // ring thread
        ringThread = new Thread(new Runnable() {
            @Override
            public void run() {

                // align second
                try {
                    TimeUnit.MILLISECONDS.sleep(1000 - System.currentTimeMillis()%1000 );
                } catch (InterruptedException e) {
                    if (!ringThreadToStop) {
                        logger.error(e.getMessage(), e);
                    }
                }

                while (!ringThreadToStop) {

                    try {
                        // second data
                        List<Integer> ringItemData = new ArrayList<>();
                        int nowSecond = Calendar.getInstance().get(Calendar.SECOND);   // 避免处理耗时太长，跨过刻度，向前校验一个刻度；
                        for (int i = 0; i < 2; i++) {
                            List<Integer> tmpData = ringData.remove( (nowSecond+60-i)%60 );
                            if (tmpData != null) {
                                ringItemData.addAll(tmpData);
                            }
                        }

                        // ring trigger
                        logger.debug(">>>>>>>>>>> xxl-job, time-ring beat : " + nowSecond + " = " + Arrays.asList(ringItemData) );
                        if (ringItemData.size() > 0) {
                            // do trigger
                            for (int jobId: ringItemData) {
                                // do trigger
                                JobTriggerPoolHelper.trigger(jobId, TriggerTypeEnum.CRON, -1, null, null, null);
                            }
                            // clear
                            ringItemData.clear();
                        }
                    } catch (Exception e) {
                        if (!ringThreadToStop) {
                            logger.error(">>>>>>>>>>> xxl-job, JobScheduleHelper#ringThread error:{}", e);
                        }
                    }

                    // next second, align second
                    try {
                        TimeUnit.MILLISECONDS.sleep(1000 - System.currentTimeMillis()%1000);
                    } catch (InterruptedException e) {
                        if (!ringThreadToStop) {
                            logger.error(e.getMessage(), e);
                        }
                    }
                }
                logger.info(">>>>>>>>>>> xxl-job, JobScheduleHelper#ringThread stop");
            }
        });
        ringThread.setDaemon(true);
        ringThread.setName("xxl-job, admin JobScheduleHelper#ringThread");
        ringThread.start();
    }

    private void refreshNextValidTime(XxlJobInfo jobInfo, Date fromTime) throws ParseException {
        Date nextValidTime = new CronExpression(jobInfo.getJobCron()).getNextValidTimeAfter(fromTime);
        if (nextValidTime != null) {
            jobInfo.setTriggerLastTime(jobInfo.getTriggerNextTime());
            jobInfo.setTriggerNextTime(nextValidTime.getTime());
        } else {
            jobInfo.setTriggerStatus(0);
            jobInfo.setTriggerLastTime(0);
            jobInfo.setTriggerNextTime(0);
        }
    }

    private void pushTimeRing(int ringSecond, int jobId){
        // push async ring
        List<Integer> ringItemData = ringData.get(ringSecond);
        if (ringItemData == null) {
            ringItemData = new ArrayList<Integer>();
            ringData.put(ringSecond, ringItemData);
        }
        ringItemData.add(jobId);

        logger.debug(">>>>>>>>>>> xxl-job, schedule push time-ring : " + ringSecond + " = " + Arrays.asList(ringItemData) );
    }

    public void toStop(){

        // 1、stop schedule
        scheduleThreadToStop = true;
        try {
            TimeUnit.SECONDS.sleep(1);  // wait
        } catch (InterruptedException e) {
            logger.error(e.getMessage(), e);
        }
        if (scheduleThread.getState() != Thread.State.TERMINATED){
            // interrupt and wait
            scheduleThread.interrupt();
            try {
                scheduleThread.join();
            } catch (InterruptedException e) {
                logger.error(e.getMessage(), e);
            }
        }

        // if has ring data
        boolean hasRingData = false;
        if (!ringData.isEmpty()) {
            for (int second : ringData.keySet()) {
                List<Integer> tmpData = ringData.get(second);
                if (tmpData!=null && tmpData.size()>0) {
                    hasRingData = true;
                    break;
                }
            }
        }
        if (hasRingData) {
            try {
                TimeUnit.SECONDS.sleep(8);
            } catch (InterruptedException e) {
                logger.error(e.getMessage(), e);
            }
        }

        // stop ring (wait job-in-memory stop)
        ringThreadToStop = true;
        try {
            TimeUnit.SECONDS.sleep(1);
        } catch (InterruptedException e) {
            logger.error(e.getMessage(), e);
        }
        if (ringThread.getState() != Thread.State.TERMINATED){
            // interrupt and wait
            ringThread.interrupt();
            try {
                ringThread.join();
            } catch (InterruptedException e) {
                logger.error(e.getMessage(), e);
            }
        }

        logger.info(">>>>>>>>>>> xxl-job, JobScheduleHelper stop");
    }

}