Cluster Configuration
Quartz's clustering features bring both high availability and scalability to your scheduler via fail-over and load balancing functionality.
Clustering currently only works with the JDBC-Jobstore (JobStoreTX or JobStoreCMT), and essentially works by having each node of the cluster share the same database.
Load-balancing occurs automatically, with each node of the cluster firing jobs as quickly as it can. When a trigger's firing time occurs, the first node to acquire it (by placing a lock on it) is the node that will fire it.
Only one node will fire the job for each firing. Meaning that, if the job has a repeating trigger that is set to fire every 10 seconds, then at 12:00:00 exactly one node will run the job, and at 12:00:10 exactly one node will run the job, and so forth. It won't necessarily be the same node each time. The selected node is chosen more or less at random. The load balancing mechanism is near-random for busy schedulers (lots of triggers) but favors the same node for non-busy (few triggers) schedulers.
Fail-over occurs when one of the nodes fails while in the midst of executing one or more jobs. When a node fails, the other nodes detect the condition and identify the jobs in the database that were in progress within the failed node. Any jobs marked for recovery (with the "requests" property on the JobDetail) will be re-executed by the remaining nodes. Jobs not marked for recovery will simply be freed up for execution at the next time a related trigger fires.
The clustering feature works best for scaling out long-running and/or CPU-intensive jobs (i.e., distributing the work-load over multiple nodes). If you need to scale out to support thousands of short-running (e.g., one second) jobs, consider partitioning the set of jobs by using multiple distinct schedulers (including multiple clustered schedulers for HA). The scheduler makes use of a cluster-wide lock, a pattern that degrades performance as you add more nodes (when going beyond about three nodes - depending upon your database's capabilities, etc.).
Enable clustering by setting the org.quartz.jobStore.isClustered property to true. Each instance in the cluster should use the same copy of the quartz.properties file. Exceptions of this would be to use properties files that are identical, with the following allowable exceptions: different thread pool size, and different value for the org.quartz.scheduler.instanceId property. Each node in the cluster must have a unique instanceId, which is easily done (without needing different properties files) by placing AUTO as the value of this property. For more information, see the configuration properties in .
Important: | Never run clustering on separate machines, unless their clocks are synchronized using some form of time-sync service (daemon) that runs very regularly (the clocks must be within a second of each other). See http://www.boulder.nist.gov/timefreq/service/its.htm if you are unfamiliar with how to do this. |
Important: | Never start (scheduler.start()) a non-clustered instance against the same set of database tables that any other instance is running (start()ed) against. Doing so will result in data corruption and erratic behavior. |
Example Properties For A Clustered Scheduler
#============================================================================
# Configure Main Scheduler Properties
#============================================================================
org.quartz.scheduler.instanceName = MyClusteredScheduler
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.oracle.OracleDelegate
org.quartz.jobStore.useProperties = false
org.quartz.jobStore.dataSource = myDS
org.quartz.jobStore.tablePrefix = QRTZ _
org.quartz.jobStore.isClustered = true
org.quartz.jobStore.clusterCheckinInterval = 20000
#============================================================================
# Configure Datasources
#============================================================================
org.quartz.dataSource.myDS.driver = oracle.jdbc.driver.OracleDriver
org.quartz.dataSource.myDS.URL = jdbc:oracle:thin:@polarbear:1521:dev
org.quartz.dataSource.myDS.user = quartz
org.quartz.dataSource.myDS.password = quartz
org.quartz.dataSource.myDS.maxConnections = 5
org.quartz.dataSource.myDS.validationQuery=select 0 from dual
|
Feedback