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ejb-timer: Example of Jakarta Enterprise Bean Timer Service - @Schedule and @Timeout

The ejb-timer quickstart demonstrates how to use the Jakarta Enterprise Bean timer service @Schedule and @Timeout annotations with {productName}.

What is it?

The ejb-timer quickstart demonstrates how to use the Jakarta Enterprise Bean timer service in {productNameFull}. This example creates a timer service that uses the @Schedule and @Timeout annotations.

The following Jakarta Enterprise Bean Timer services are demonstrated:

  • @Schedule: Uses this annotation to mark a method to be executed according to the calendar schedule specified in the attributes of the annotation. This example schedules a message to be printed to the server console every 6 seconds.

  • @Timeout: Uses this annotation to mark a method to execute when a programmatic timer goes off. This example sets the timer to go off every 3 seconds, at which point the method prints a message to the server console.

Access the Application

This application only prints messages to stdout. Each timeout callback logs the class name of the @Singleton bean that created the timer, an identifier of the timer, and the timestamp of the callback. In our example application, the ScheduleExample bean creates a persistent timer, while the TimeoutExample creates a non-persistent (i.e. transient) timer. To see it working, check the server log. You should see similar output:

INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:04:24.896811Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:27.002334Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:30.004340Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:04:30.014526Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:33.001997Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:36.001444Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:04:36.004266Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:39.001746Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:42.002048Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:04:42.010535Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:45.000920Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:48.001840Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:04:48.010532Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:51.002591Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-331711014] at 2022-05-04T21:04:54.001734Z

Existing threads in the thread pool handle the invocations. They are rotated and the name of the thread that handles the invocation is printed within the parenthesis (EJB Default - #).

To demonstrate the behavioral difference between persistent and non-persistent timers, stop the server via "CRTL-C" and restart it. Upon restart, you will see similar periodic timeout events, but while the persistent timer identifier remains the same, since persistent timers were restore upon restart; the non-persistent timer now has a different identifier, since the transient timers are lost when the server shutdown, and was recreated on startup.

INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:18:36.013024Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:39.001383Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:42.002232Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:18:42.011380Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:45.001951Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:48.002369Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:18:48.008104Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:51.002364Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:54.002230Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:18:54.009333Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:18:57.001874Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:19:00.002287Z
INFO  [stdout] (EJB default - 1) Timeout received for ScheduleExample[-2138907176] at 2022-05-04T21:19:00.010617Z
INFO  [stdout] (EJB default - 1) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:19:03.002128Z
INFO  [stdout] (EJB default - 2) Timeout received for TimeoutExample[-1065503193] at 2022-05-04T21:19:06.002358Z

Using Timer Service within a cluster

To demonstrate distributed TimerService behavior, a cluster of at least two application server instances must be started. Begin by making a copy of the entire {productName} directory to be used as second cluster member. Note that the example can be run on a single node as well, but without observation of the singleton properties.

The default configuration of the HA profiles is pre-configured for a fully distributed persistent timers, as well as passivation support for non-persistent timers.

Start the two {productName} servers with the same HA profile using the following commands. Note that a socket binding port offset and a unique node name must be passed to the second server if the servers are binding to the same host.

$ {jbossHomeName}_1/bin/standalone.sh -c standalone-ha.xml -Djboss.node.name=node1
$ {jbossHomeName}_2/bin/standalone.sh -c standalone-ha.xml -Djboss.node.name=node2 -Djboss.socket.binding.port-offset=100
Note
 For Windows, use the {jbossHomeName}_1\bin\standalone.bat and {jbossHomeName}_2\bin\standalone.bat scripts.

This example is not limited to two servers. Additional servers can be started by specifying a unique port offset for each one.

Next, use the following commands to deploy the already built demo application archive to each server. Note that since the default socket binding port is 9990 and the second server has ports offset by 100, the sum, 10090 must be passed as an argument to the deploy maven goal.

mvn wildfly:deploy
mvn wildfly:deploy -Dwildfly.port=10090

Once deployed, you should begin to see log messages for our timer events. However, while timeout events for the non-persistent timer created by the TimoutExample bean are triggered on both nodes, timeout events for the persistent timer created by the ScheduleExample bean are only triggered on one node.

node1:

INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:36.003154Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:39.003098Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:42.002884Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:45.003209Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:48.001284Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:51.001656Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:54.001396Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:57:57.001848Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:58:00.001673Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[390846799] at 2022-05-05T20:58:03.001794Z

node2:

INFO  [stdout] (TimerScheduler - 1) Timeout received for ScheduleExample[-392733837] at 2022-05-05T20:57:36.003800Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:36.003799Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:39.003279Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:42.003483Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for ScheduleExample[-392733837] at 2022-05-05T20:57:42.003699Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:45.003339Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for ScheduleExample[-392733837] at 2022-05-05T20:57:48.001545Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:48.001544Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:51.001657Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:54.001710Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for ScheduleExample[-392733837] at 2022-05-05T20:57:54.001710Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:57:57.001717Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for ScheduleExample[-392733837] at 2022-05-05T20:58:00.001091Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:58:00.001547Z
INFO  [stdout] (TimerScheduler - 1) Timeout received for TimeoutExample[1048239741] at 2022-05-05T20:58:03.001514Z

If you then shutdown the node on which the ScheduleExample timeouts appear (in our case, node2), the other node (in our case, node1) will promptly begin receiving timeouts for that same persistent timer (as indicated by the same identifier).

Restarting the node that we previously shutdown (in our case, node2), using the same command as listed above), you should observe that timeouts for the ScheduleExample timer will resume on the original node (in our case, node2), and now the other node (in our case, node1) no longer receives those timeout events. In fact, if you collate the timestamps for the ScheduleExample bean across each server log carefully, you should find that no events were skipped, and no duplicate events were received.