Scheduling the trigger of a function

Kubeless has its own CronJobTrigger which uses Kubernetes CronJob to trigger your function in a given schedule. On this page, we're going to cover how to use it, and some basic features.

Creating a new CronJobTrigger

You can create a new cron trigger using kubeless-cli. In this section, we're going to show you how to create a simple function that logs Hello world! every 1 minute.

For this example you're going to need the following tools:

After installing all the requirements, you can proceed to the step-by-step guide:

Step 1: Create a new Minikube cluster

In this step, you're going to create a new Minikube cluster called kubeless, where you're going to deploy the function triggers. You can run the following command on your shell:

minikube start -p kubeless

IMPORTANT: If you have already created any Minikube cluster called kubeless you should delete it first, with minikube delete -p kubeless

Step 2: Install Kubeless on your cluster

Now that you have a Minikube cluster running, you can run the following command to install the latest version of Kubeless:

RELEASE=$(curl -s https://api.github.com/repos/kubeless/kubeless/releases/latest | grep tag_name | cut -d '"' -f 4) && \
  kubectl create ns kubeless && \
  kubectl create -f https://github.com/kubeless/kubeless/releases/download/$RELEASE/kubeless-$RELEASE.yaml

Step 3: Deploy a test function

For this CronJob test, we're going to use a simple function that just logs a "Hello world!" message. Since this isn't a tutorial explaining how to deploy a function you can just run the following command:

 kubectl apply -f https://gist.githubusercontent.com/odelucca/1f3a71b7ff05f31d492dc5bfd3f3afba/raw/5237991f018f99a697e937a85e60e57dd8ac1a1c/function.yaml

Step 4: Create a new CronJob trigger

To create a CronJob trigger with kubeless-cli you can run the following command:

kubeless trigger cronjob create \
  cron-test-hello-world \
  --function cron-test-hello-world \
  --schedule "*/1 * * * *"

About the provided arguments:

The first argument must be the trigger name you want to use
--function should be the name of the function you want to trigger with that cron
--schedule the cron pattern to trigger your function

Step 5: Take a look on your function logs

Now, wait 1 or 2 minutes and take a look at your function logs with this command:

kubeless function logs cron-test-hello-world

You should see some Hello world! logs, showing that our CronJob is working as expected.

Advanced concepts

In this section, we're going to cover some advanced concepts regarding the CronJob trigger. Each item in this section will cover a given feature that you can use on your triggers.

Passing payload data to the function

While triggering a function you could pass also a payload data to it. Those will be available on event.data (like any other request data). You can do so with the following command:

kubeless trigger cronjob (create or update) --payload <stringified JSON>

If you're not willing to provide a stringified JSON to the --payload argument, you can use --payload-from-file instead and pass a file path. You can provide files on the following extensions:

.json
.yaml

IMPORTANT: Your payload must be an object, so you cannot provide a JSON array to it, but you can add a key on your object that can contain a list of items instead.

Documentation