Kamelets Binding Error Handler example

This example shows how to create a simple source Kamelet which sends periodically events (and certain failures). The events are consumed by a log sink in a KameletBinding. With the support of the ErrorHandler we will be able to redirect all errors to a Dead Letter Channel error-handler Kamelet.

Incremental ID Source Kamelet

First of all, you must install the incremental-id-source Kamelet defined in incremental-id-source.kamelet.yaml file. This source will emit events every second with an autoincrement counter that will be forced to fail when the number 0 is caught. With this trick, we will simulate possible event faults.

$ kubectl apply -f incremental-id-source.kamelet.yaml

You can check the newly created kamelet checking the list of kamelets available:

$ kubectl get kamelets

NAME                            PHASE
incremental-id-source           Ready

Log Sink Kamelet

Now it's the turn of installing the log-sink_ Kamelet defined in log-sink.kamelet.yaml file:

$ kubectl apply -f log-sink.kamelet.yaml

You can check the newly created kamelet checking the list of kamelets available:

$ kubectl get kamelets

NAME                    PHASE
log-sink                Ready
incremental-id-source   Ready

Error handler Kamelet

We finally install an error handler as specified in error-handler.kamelet.yaml file. This is a simple logger, but you can use any endpoint to collect and store the failing events.

$ kubectl apply -f error-handler.kamelet.yaml

You can check the newly created kamelet checking the list of kamelets available:

$ kubectl get kamelets

NAME                    PHASE
error-handler           Ready
log-sink                Ready
incremental-id-source   Ready

Error Handler Kamelet Binding

We can create a KameletBinding which is started by the incremental-id-source Kamelet and log events to log-sink Kamelet. As this will sporadically fail, we can configure an errorHandler with the error-handler Kamelet as Dead Letter Channel. We want to configure also some redelivery policies. We can declare it as in kamelet-binding-error-handler.yaml file:

...
  errorHandler:
    dead-letter-channel:
      endpoint:
        ref:
          kind: Kamelet
          apiVersion: camel.apache.org/v1alpha1
          name: error-handler
        properties:
          message: "ERROR!"
      parameters:
        maximumRedeliveries: 3
        redeliveryDelay: 2000

Execute the following command to start the Integration:

kubectl apply -f kamelet-binding-error-handler.yaml

As soon as the Integration starts, it will log the events on the ok log channel and errors on the error log channel:

[1] 2021-04-21 13:03:43,773 INFO  [sink] (Camel (camel-1) thread #0 - timer://tick) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Producing message #8]
[1] 2021-04-21 13:03:44,774 INFO  [sink] (Camel (camel-1) thread #0 - timer://tick) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Producing message #9]
[1] 2021-04-21 13:03:45,898 INFO  [error-sink] (Camel (camel-1) thread #0 - timer://tick) Exchange[ExchangePattern: InOnly, BodyType: String, Body: ERROR!]
[1] 2021-04-21 13:09:46,775 INFO  [sink] (Camel (camel-1) thread #0 - timer://tick) Exchange[ExchangePattern: InOnly, BodyType: String, Body: Producing message #11]

This example is useful to guide you through the configuration of an error handler. In a production environment you will likely configure the error handler Kamelet pointing to a persistent queue.