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commit af26e5992a17fc6c81b5149a985ef12b7c4e2582
Author: Kuthumi Pepple <kuthumipep...@gmail.com>
AuthorDate: Wed Jun 15 11:14:42 2022 +0100
improve README.md
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-# Camel K cron examples
+# Camel K Cron Examples
-Find useful examples about how to create a cron route in Camel K.
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+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](https://camel.apache.org).
+
+
+## Requirements for running this example
+
+**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.
+
+### Optional Requirements
+
+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](https://marketplace.visualstudio.com/items?itemName=redhat.apache-camel-extension-pack)
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.
+
+## Preparing the cluster
+In order to follow this example:
+- Create a namespace called `camel-cron` and set that namespace as default.
+- Install the Camel K operator in that namespace. In most cases, running
`kamel install` should be enough. If not, you can read the [installation
instructions for your specific cluster
here](https://camel.apache.org/camel-k/latest/installation/installation.html).
+
+## Understanding the Example
+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`
+
+## Running the Example
+
+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
+
+## Modifying the Cron expression
+
+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](./cron.groovy)
+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](./cron.groovy)
+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
+
+## Uninstall
+
+To cleanup everything, execute the following command:
+```
+kubectl delete namespace camel-cron
+```
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