背景
我正在尝试使用jdbc在集群模式下使用石英调度器。
问题
在开始使用jdbc集群模式之前，我只是测试了RAM存储中的调度程序。那个没有问题，我能够重新启动调度程序（主类）而不出现任何错误。现在我的问题是，当我停止执行（ctrl+c），然后重新启动它时，我总是收到错误消息：
org.quartz.ObjectAlreadyExistsException: Unable to store Job : 'MyTestJob', because one already exists with this identification.
我不明白这里发生了什么。Quartz是否不支持重新启动调度程序？我的意思是，如果发生崩溃并在恢复后重新启动调度程序，会发生什么？难道唯一的选择就是从Quartz数据库中删除作业吗？也许我错过了其他方法或东西。我不太喜欢使用不能处理重新启动的库。
另一个奇怪的事情是，当切换到JDBC时，我的作业不再被触发，我只在数据库中看到WAITING状态。这可能是什么原因？作业（cron-schedule）在RAM模式下没有问题。
我对这个简单任务的文档水平和遇到的问题有些惊讶，因为我多年来一直听说过Quartz调度程序，但从未开始使用过。Google建议我不是唯一遇到这个问题的人。我希望这只是我自己的问题，而且我的问题有一个简单的解决方案，否则，在2.2.x版本中尝试这个库并已经需要寻找其他东西将会非常令人失望。
以下是我的配置：
#============================================================================
# Configure Main Scheduler Properties
#============================================================================
org.quartz.scheduler.skipUpdateCheck = true
org.quartz.scheduler.instanceName = Test-Scheduler
org.quartz.scheduler.instanceId = AUTO
#============================================================================
# Configure ThreadPool
#============================================================================
org.quartz.threadPool.class = org.quartz.simpl.SimpleThreadPool
org.quartz.threadPool.threadCount = 25
org.quartz.threadPool.threadPriority = 5
#============================================================================
# Configure JobStore
#============================================================================
org.quartz.jobStore.misfireThreshold = 60000
org.quartz.jobStore.class = org.quartz.impl.jdbcjobstore.JobStoreTX
org.quartz.jobStore.driverDelegateClass = org.quartz.impl.jdbcjobstore.StdJDBCDelegate
org.quartz.jobStore.useProperties = true
org.quartz.jobStore.dataSource = quartzDS
org.quartz.jobStore.tablePrefix = QRTZ_
org.quartz.jobStore.isClustered = true
org.quartz.jobStore.clusterCheckinInterval = 20000
这是我的代码：
SchedulerFactory sf = new StdSchedulerFactory();
Scheduler scheduler = sf.getScheduler();
scheduler.start();
JobDetail jobDetail = newJob(job.getClass())
.withIdentity("test-name", "test-group")
.build();
CronTrigger trigger = newTrigger()
.withIdentity("test-name-trigger", "test-group")
.withSchedule(cronSchedule("0 0/1 * * * ?"))
.build();
scheduler.scheduleJob(jobDetail, trigger);
System.out.println(trigger.getNextFireTime());
编辑
这很有趣。
1）RAM模式可行。
2）启用集群的jdbc不可行并且会默默失败 - 即使启用了日志记录。在日志输出中，我看到以下内容：
19:57:29,913 INFO StdSchedulerFactory:1184 - Using default implementation for ThreadExecutor
19:57:29,936 INFO SchedulerSignalerImpl:61 - Initialized Scheduler Signaller of type: class org.quartz.core.SchedulerSignalerImpl
19:57:29,936 INFO QuartzScheduler:240 - Quartz Scheduler v.2.2.1 created.
19:57:29,938 INFO JobStoreTX:667 - Using db table-based data access locking (synchronization).
19:57:29,940 INFO JobStoreTX:59 - JobStoreTX initialized.
19:57:29,941 INFO QuartzScheduler:305 - Scheduler meta-data: Quartz Scheduler (v2.2.1) 'Test-Scheduler' with instanceId 'Michael-PC1405447049916'
Scheduler class: 'org.quartz.core.QuartzScheduler' - running locally.
NOT STARTED.
Currently in standby mode.
Number of jobs executed: 0
Using thread pool 'org.quartz.simpl.SimpleThreadPool' - with 25 threads.
Using job-store 'org.quartz.impl.jdbcjobstore.JobStoreTX' - which supports persistence. and is clustered.
19:57:29,941 INFO StdSchedulerFactory:1339 - Quartz scheduler 'Test-Scheduler' initialized from default resource file in Quartz package: 'quartz.properties'
19:57:29,941 INFO StdSchedulerFactory:1343 - Quartz scheduler version: 2.2.1
19:57:29,995 INFO AbstractPoolBackedDataSource:462 - Initializing c3p0 pool... com.mchange.v2.c3p0.ComboPooledDataSource [ acquireIncrement -> 3, acquireRetryAttempts -> 30, acquireRetryDelay -> 1000, autoCommitOnClose -> false, automaticTestTable -> null, breakAfterAcquireFailure -> false, checkoutTimeout -> 0, connectionCustomizerClassName -> null, connectionTesterClassName -> com.mchange.v2.c3p0.impl.DefaultConnectionTester, dataSourceName -> 1hgeby993gf1xpdmdc44s|7ec4d0, debugUnreturnedConnectionStackTraces -> false, description -> null, driverClass -> com.mysql.jdbc.Driver, factoryClassLocation -> null, forceIgnoreUnresolvedTransactions -> false, identityToken -> 1hgeby993gf1xpdmdc44s|7ec4d0, idleConnectionTestPeriod -> 50, initialPoolSize -> 3, jdbcUrl -> jdbc:mysql://localhost:3306/scheduler, maxAdministrativeTaskTime -> 0, maxConnectionAge -> 0, maxIdleTime -> 0, maxIdleTimeExcessConnections -> 0, maxPoolSize -> 5, maxStatements -> 0, maxStatementsPerConnection -> 120, minPoolSize -> 1, numHelperThreads -> 3, numThreadsAwaitingCheckoutDefaultUser -> 0, preferredTestQuery -> SELECT 1 FROM QRTZ_JOB_DETAILS, properties -> {user=******, password=******}, propertyCycle -> 0, testConnectionOnCheckin -> true, testConnectionOnCheckout -> false, unreturnedConnectionTimeout -> 0, usesTraditionalReflectiveProxies -> false ]
19:57:30,243 DEBUG StdRowLockSemaphore:107 - Lock 'TRIGGER_ACCESS' is desired by: main
19:57:30,262 DEBUG StdRowLockSemaphore:92 - Lock 'TRIGGER_ACCESS' is being obtained: main
19:58:21,328 DEBUG StdRowLockSemaphore:141 - Lock 'TRIGGER_ACCESS' was not obtained by: main - will try again.
19:58:22,329 DEBUG StdRowLockSemaphore:92 - Lock 'TRIGGER_ACCESS' is being obtained: main
19:59:13,389 DEBUG StdRowLockSemaphore:141 - Lock 'TRIGGER_ACCESS' was not obtained by: main - will try again.
19:59:14,389 DEBUG StdRowLockSemaphore:92 - Lock 'TRIGGER_ACCESS' is being obtained: main
虽然，就在我准备再次启用集群模式的时候，我看到了异常：
Exception in thread "main" org.quartz.impl.jdbcjobstore.LockException: Failure obtaining db row lock: Lock wait timeout exceeded; try restarting transaction [See nested exception: java.sql.SQLException: Lock wait timeout exceeded; try restarting transaction]
at org.quartz.impl.jdbcjobstore.StdRowLockSemaphore.executeSQL(StdRowLockSemaphore.java:157)
at org.quartz.impl.jdbcjobstore.DBSemaphore.obtainLock(DBSemaphore.java:113)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.executeInNonManagedTXLock(JobStoreSupport.java:3780)
at org.quartz.impl.jdbcjobstore.JobStoreTX.executeInLock(JobStoreTX.java:93)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.clearAllSchedulingData(JobStoreSupport.java:1956)
at org.quartz.core.QuartzScheduler.clear(QuartzScheduler.java:1572)
at org.quartz.impl.StdScheduler.clear(StdScheduler.java:239)
at com.scs.core.cron.TaskRunner.main(TaskRunner.java:52)
3) 在禁用集群的jdbc模式下，也无法正常工作, 但是会收到一个异常：
20:04:15,993 DEBUG SimpleSemaphore:132 - Lock 'TRIGGER_ACCESS' retuned by: main
20:04:15,993 DEBUG JobStoreTX:703 - JobStore background threads started (as scheduler was started).
20:04:15,994 INFO QuartzScheduler:575 - Scheduler Test-Scheduler_$_NON_CLUSTERED started.
20:04:15,994 DEBUG JobStoreTX:3933 - MisfireHandler: scanning for misfires...
20:04:16,000 DEBUG JobStoreTX:3182 - Found 0 triggers that missed their scheduled fire-time.
20:04:16,004 DEBUG QuartzSchedulerThread:276 - batch acquisition of 0 triggers
20:04:16,008 DEBUG SimpleSemaphore:81 - Lock 'TRIGGER_ACCESS' is desired by: main
20:04:16,008 DEBUG SimpleSemaphore:88 - Lock 'TRIGGER_ACCESS' is being obtained: main
20:04:16,008 DEBUG SimpleSemaphore:105 - Lock 'TRIGGER_ACCESS' given to: main
20:04:16,052 DEBUG SimpleSemaphore:132 - Lock 'TRIGGER_ACCESS' retuned by: main
Found job: class to.test.cron.ImportProducts
Tue Jul 15 20:05:00 CEST 2014
isStarted=true
isShutdown=false
isInStandbyMode=false
20:04:16,058 DEBUG QuartzSchedulerThread:276 - batch acquisition of 0 triggers
20:04:42,961 ERROR ErrorLogger:2425 - An error occurred while scanning for the next triggers to fire.
org.quartz.JobPersistenceException: Couldn't acquire next trigger: to.test.cron.ImportProducts [See nested exception: java.lang.ClassNotFoundException: to.test.cron.ImportProducts]
at org.quartz.impl.jdbcjobstore.JobStoreSupport.acquireNextTrigger(JobStoreSupport.java:2848)
at org.quartz.impl.jdbcjobstore.JobStoreSupport$40.execute(JobStoreSupport.java:2759)
at org.quartz.impl.jdbcjobstore.JobStoreSupport$40.execute(JobStoreSupport.java:2757)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.executeInNonManagedTXLock(JobStoreSupport.java:3787)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.acquireNextTriggers(JobStoreSupport.java:2756)
at org.quartz.core.QuartzSchedulerThread.run(QuartzSchedulerThread.java:272)
Caused by: java.lang.ClassNotFoundException: to.test.cron.ImportProducts
at java.net.URLClassLoader$1.run(Unknown Source)
at java.net.URLClassLoader$1.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
at java.lang.ClassLoader.loadClass(Unknown Source)
at org.quartz.simpl.InitThreadContextClassLoadHelper.loadClass(InitThreadContextClassLoadHelper.java:72)
at org.quartz.simpl.CascadingClassLoadHelper.loadClass(CascadingClassLoadHelper.java:114)
at org.quartz.simpl.CascadingClassLoadHelper.loadClass(CascadingClassLoadHelper.java:138)
at org.quartz.impl.jdbcjobstore.StdJDBCDelegate.selectJobDetail(StdJDBCDelegate.java:852)
at org.quartz.impl.jdbcjobstore.JobStoreSupport.acquireNextTrigger(JobStoreSupport.java:2816)
... 5 more
我不太理解为什么在三种不同的模式下会出现三种完全不同的行为。如果类可以在RAM模式下找到，为什么不能在jdbc模式下找到？而在集群模式下为什么没有被记录？该类实际上是在OSGI类型的模块中。这会引起问题吗（在jdbc模式下）？是否有什么我可以做的，使得该类可以被找到，例如通过将类加载器传递给quartz等方式？
我现在很迷茫，非常感谢任何帮助。如果只能回到标准的cron作业，那将是一件遗憾的事情，特别是因为quartz有更多的优势。
提前感谢您提供的任何帮助，
迈克尔