This example demonstrates how you can create cron routes in Camel K.
You can find more information about Apache Camel and Apache Camel K on the official Camel website.
Kubectl CLI The Kubernetes kubectl CLI tool will be used to interact with the Kubernetes cluster.
Connection to a Kubernetes cluster You need to connect to a Kubernetes cluster in order to run the example.
Apache Camel K CLI (“kamel”) You need the Apache Camel K CLI (“kamel”) in order to access all Camel K features.
The following requirements are optional. They don't prevent the execution of the demo, but may make it easier to follow.
VS Code Extension Pack for Apache Camel The VS Code Extension Pack for Apache Camel provides a collection of useful tools for Apache Camel K developers, such as code completion and integrated lifecycle management. They are recommended for the tutorial, but they are not required. You can install it from the VS Code Extensions marketplace.
In order to follow this example:
camel-cron and set that namespace as default.kamel install should be enough. If not, you can read the installation instructions for your specific cluster here.This example uses the cron component to trigger a route at a specific time interval specified in a cron expression. The route transforms data from the cron source and sends it to the logger.
The integration is all contained in a single file named cron.groovy
This example is a Camel K integration that is scheduled to run periodically, printing “Hello Camel K using CronJob” once every minute.
Use the following command to run it:
kamel run cron.groovy
The build phase may take some seconds to complete. When it finishes, if everything is okay, the integration should be running periodically every minute.
To view the logs of the running integration, run the command:
kamel log cron
You should see the Camel K integration start, print “Hello Camel K using CronJob” and shutdown periodically every minute in the terminal window.
You can terminate the log stream with Ctrl+C
To confirm that the integration is being run as a Kubernetes Cronjob, run:
kubectl get cronjob
You should see a Kubernetes CronJob named “cron” with the specified schedule.
To see the pods starting and being destroyed, run:
kubectl get pod -w
Hit Ctrl+C to exit
Run the integration in “dev mode” in order to see the logs in the terminal:
kamel run cron.groovy --dev
Since the integration is running in dev mode, you can change the integration code and Camel K will redeploy the changes automatically.
Change the cron expression:
open the cron.groovy file and change the first endpoint from cron:tab?schedule=*+*+*+*+? to cron:tab?schedule=*/2+*+*+*+?, then save the file.
You should see the new integration starting up in the terminal window and replacing the old one. It should print “Hello Camel K using CronJob” once every 2 minutes in the terminal window.
Note: Cron only allows for a minimum of 1 minute apart between jobs
Change the cron expression again:
open the cron.groovy file and change the first endpoint to cron:tab?schedule=*/3+*+*+*+?, then save the file.
Now, after a few seconds, it should print “Hello Camel K using CronJob” once every 3 minutes in the terminal.
Hit Ctrl+C to exit dev mode and terminate execution
To cleanup everything, execute the following command:
kubectl delete namespace camel-cron