Example 14 - Trigger Priorities
This example will demonstrate how you can use trigger priorities to manage firing order for triggers with the same fire time.
The program will perform the following actions:
Create a scheduler with a single worker thread
Schedule three triggers with different priorities that fire the first time at the same time, and a second time at staggered intervals
Start up the Quartz Scheduler
Wait for 30 seconds to give Quartz a chance to fire the triggers
Shut down the scheduler
Running the Example
This example can be executed from the examples/example14 directory. There are two ways to run this example
example14.sh - A UNIX/Linux shell script
example14.bat - A Windows Batch file
Expected Results
Each of the three triggers should fire twice. Once in order of priority, as they all start at the same time, and a second time in order of their staggered firing times. You should see something like this in the log or on the console:
INFO 15 Aug 12:15:51.345 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: Priority10Trigger15SecondRepeat
INFO 15 Aug 12:15:51.345 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: Priority5Trigger10SecondRepeat
INFO 15 Aug 12:15:51.345 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: PriorityNeg5Trigger5SecondRepeat
INFO 15 Aug 12:15:56.220 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: PriorityNeg5Trigger5SecondRepeat
INFO 15 Aug 12:16:01.220 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: Priority5Trigger10SecondRepeat
INFO 15 Aug 12:16:06.220 PM PriorityExampleScheduler_Worker-0
org.quartz.examples.example14.TriggerEchoJob
TRIGGER: Priority10Trigger15SecondRepeat
The Code
The code for this example resides in the package org.quartz.examples.example14.
The code in this example is made up of the following classes:
Class Name | Description |
PriorityExample | The main program. |
TriggerEchoJob | A simple job that echoes the name if the Trigger that fired it. |
TriggerEchoJob
TriggerEchoJob is a simple job that implements the Job interface and writes the name of the trigger that fired it to the log (by default, this will simply go to the screen):
public void execute(JobExecutionContext context) throws JobExecutionException {
LOG.info("TRIGGER: " + context.getTrigger().getKey());
}
PriorityExample
The program starts by getting an instance of the Scheduler. This is done by creating a StdSchedulerFactory and then using it to create a scheduler.
SchedulerFactory sf = new StdSchedulerFactory(
"org/quartz/examples/example14/quartz_priority.properties");
Scheduler sched = sf.getScheduler();
We pass a specific Quartz properties file to the StdSchedulerFactory to configure our new Scheduler instance. These properties will create a RAM-based scheduler with only one worker thread so that we can see priorities act as the tie breaker when triggers compete for the single thread, quartz_priority.properties:
org.quartz.scheduler.instanceName=PriorityExampleScheduler
# Set thread count to 1 to force Triggers scheduled for the same time to
# to be ordered by priority.
org.quartz.threadPool.threadCount=1
org.quartz.threadPool.class=org.quartz.simpl.SimpleThreadPool
org.quartz.jobStore.class=org.quartz.simpl.RAMJobStore
The TriggerEchoJob is defined as a job to Quartz using the JobDetail class. As shown below, it passes "null" for its group, so it will use the default group:
JobDetail job = new JobDetail("TriggerEchoJob", null, TriggerEchoJob.class);
We create three SimpleTriggers that will all fire the first time five seconds from now but with different priorities, and then fire a second time at staggered five second intervals:
// Calculate the start time of all triggers as 5 seconds from now
Date startTime = futureDate(5, IntervalUnit.SECOND);
// First trigger has priority of 1, and will repeat after 5 seconds
Trigger trigger1 = newTrigger()
.withIdentity("PriorityNeg5Trigger5SecondRepeat")
.startAt(startTime)
.withSchedule(simpleSchedule().withRepeatCount(1).withIntervalInSeconds(5))
.withPriority(1)
.forJob(job)
.build();
// Second trigger has default priority of 5 (default), and will repeat after 10 seconds
Trigger trigger2 = newTrigger()
.withIdentity("Priority5Trigger10SecondRepeat")
.startAt(startTime)
.withSchedule(simpleSchedule().withRepeatCount(1).withIntervalInSeconds(10))
.forJob(job)
.build();
// Third trigger has priority 10, and will repeat after 15 seconds
Trigger trigger3 = newTrigger()
.withIdentity("Priority10Trigger15SecondRepeat")
.startAt(startTime)
.withSchedule(simpleSchedule().withRepeatCount(1).withIntervalInSeconds(15))
.withPriority(10)
.forJob(job)
.build();
We now associate the three triggers with our job in the scheduler. The first time we need to also add the job itself to the scheduler:
// Tell quartz to schedule the job using our trigger
sched.scheduleJob(job, trigger1);
sched.scheduleJob(trigger2);
sched.scheduleJob(trigger3);
At this point, the triggers have been scheduled to run. However, the scheduler is not yet running, so we must tell it to start up.
sched.start();
To let the scheduler have an opportunity to run the job, our program sleeps for 30 seconds. The scheduler is running in the background and should fire the job six times during those 30 seconds.
Thread.sleep(30L * 1000L);
Finally, the program gracefully shuts down the scheduler:
sched.shutdown(true);
Note: | Passing "true" to the shutdown method tells Quartz Scheduler to wait until all jobs have completed running before returning from the method call. |
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