Cron Job Scheduler Sample

Cron Job Scheduler

This implementation of the Java interface JobScheduler is based on the Quartz job scheduling project and the PooledExecutor of Doug Leas Concurrency Package as a ThreadPool implementation for the Quartz Scheduler.

WARNING: Consider the JobScheduler interface as beta in terms of defined functionality as it will be extended with additional requirements in the near future (i.e. getJobList).

This QuartzJobScheduler implementation is written as a standard Avalon component. So, its definition you'll find in the cocoon.xconf file of Cocoon if you've included the cron-block in your build (see block.properties or local.block.properties file respectively).

The snippet below shows the configuration example of the component itself:

There is nothing special about it. As you could see from the snippet above, inside the job scheduler component definition there are two parts:

ThreadPool definition
Trigger definitions

ThreadPool

The ThreadPool definition look like this:

<thread-pool>  <use-queueing>false</use-queueing>  <queue-size>-1</queue-size>  <max-pool-size>-1</max-pool-size>  <min-pool-size>1</min-pool-size>  <keep-alive-time-ms>60000</keep-alive-time-ms>  <block-policy>RUN</block-policy>  <shutdown-graceful>true</shutdown-graceful>  <shutdown-wait-time-ms>5000</shutdown-wait-time-ms> </thread-pool>

As mentioned in the beginning, more information about the thread pool details of the base PooledExecutor class can be found there.

Triggers

The trigger definition section consists of a single <triggers> element with as much as needed <trigger> elements inside it. A <trigger> element looks like:

<triggers>  <trigger name="test-job1" target="org.apache.cocoon.components.cron.CronJob/test" concurrent-runs="false"> <cron>*/12 * * * * ? *</cron> </trigger> <trigger name="test-job2" target="org.apache.cocoon.components.cron.CronJob/test" concurrent-runs="true"> <seconds>*/12</seconds> <minutes>*/5</minutes> <hours>8,10,12,14,16,18</hours> <days>?</days> <months>*</months> <weekdays>SUN-FRI</weekdays> </trigger> </triggers>

The <cron> element is simply the concatenation of the values of the elements <seconds>, <minutes>, <hours>, <days>, <months>, <weekdays>, and <year> delimeted with spaces. You can use either form but the <cron> element will be preferred by the implementation if you use both forms together in one <trigger> element. A description of the expressions used inside the <trigger> elements is described in the CronTrigger class.

Job Components

The CronJob object doing your work can be defined in the cocoon.xconf file as a regular Avalon components. The role attribute given to this component is refered to by the target attribute in the <trigger> element above. Below is the sample for the TestCronJob component.

<component role="org.apache.cocoon.components.cron.CronJob/test" class="org.apache.cocoon.components.cron.TestCronJob" logger="cron.test"> <msg>I'm here</msg> <sleep>23000</sleep> </component>