Apache Camel source

These samples show how to configure a Camel Source. It is an Event Source that can leverage one of the 250+ Apache Camel components for generating events.

Prerequisites

  1. Install Knative Serving and Eventing.

  2. Install the Apache Camel K Operator in any namespace where you want to run Camel sources.

The preferred version that is compatible with Camel sources is Camel K v0.3.3.

Installation instructions are provided in the Apache Camel K GitHub repository. Documentation includes specific instructions for common Kubernetes environments, including development clusters.

1.(Optional) Download Kail binaries for Linux or OSX, which can be found on the latest release page. You can use kail instead of kubectl logs to tail the logs of the subscriber.

  1. Install the Camel Source from the camel.yaml in the Eventing Sources release page:
   kubectl apply --filename camel.yaml

Create a Channel and a Subscriber

To check if a CamelSource is fully working, create:

  • a simple Knative event display service that prints incoming events to its log
  • an in-memory channel named camel-test that buffers events created by the event source
  • a subscription to direct events from the test channel to the event display service

Deploy the display_resources.yaml:

kubectl apply --filename display_resources.yaml

Run a CamelSource using the Timer component

The samples directory contains some sample sources that can be used to generate events.

The simplest example of the CamelSource, that does not require additional configuration, is the “timer” source.

If you want, you can customize the source behavior using options available in the Apache Camel documentation for the timer component. All Camel components are documented in the Apache Camel GitHub repository.

Install the timer CamelSource from source:

kubectl apply -f source_timer.yaml

Verify that the published events were sent into the Knative eventing system by looking at what is downstream of the CamelSource.

kubectl logs --selector serving.knative.dev/service=camel-event-display -c user-container

or

You can also use kail to tail the logs of the subscriber.

kail -d camel-event-display --since=10m

If you have deployed the timer source, you should see log lines appearing every 3 seconds.

Run a CamelSource using the Telegram component

Another useful component available with Camel is the Telegram component. It can be used to forward messages of a Telegram chat into Knative channels as events.

Before using the provided Telegram CamelSource example, you need to follow the instructions on the Telegram website for creating a Telegram Bot. The quickest way to create a bot is to contact the Bot Father, another Telegram Bot, using your preferred Telegram client (mobile or web). After you create the bot, you will receive an authorization token that is needed for the source to work.

First, edit the telegram CamelSource and put the authorization token, replacing the <put-your-token-here> placeholder.

To reduce noise in the event display, you can remove the previously created timer CamelSource from the namespace:

kubectl delete camelsource camel-timer-source

Install the telegram CamelSource from source:

kubectl apply -f source_telegram.yaml

Start kail again and keep it open on the event display:

kail -d camel-event-display --since=10m

Now, you can contact your bot with any Telegram client. Each message you send to the bot will be printed by the event display as a cloudevent.

Run a Camel K Source

For complex use cases that require multiple steps to be executed before event data is ready to be published, you can use Camel K sources. Camel K lets you use Camel DSL to design one or more routes that can define complex workflows before sending events to the target sink.

If you have previously deployed other CamelSources, to reduce noise in the event display, you can remove them all from the namespace:

kubectl delete camelsource --all

Install the Camel K Source from source:

kubectl apply -f source_camel_k.yaml

Start kail again and keep it open on the event display:

kail -d camel-event-display --since=10m

The event display will show some JSON data periodically pulled from an external REST API. The API in the example is static, but you can use your own dynamic API by replacing the endpoint.