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Apache Camel source
These samples show how to configure Camel Sources. These event sources are highly dynamic and allow you to generate events from a variety of systems (cloud platforms, social networks, datastores, message brokers, legacy systems, etc.), leveraging all the 300+ components provided by Apache Camel.
All Camel Sources use Apache Camel K as the runtime engine.
Prerequisites
-
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 v1.0.0-M4.
Installation instructions are provided in the Apache Camel K Manual. Documentation includes specific instructions for common Kubernetes environments, including development clusters.
-
Install the Camel Source from the
camel.yaml
in the Eventing Sources release page:kubectl apply --filename camel.yaml
Create Test Resources
All the CamelSource
examples use some test resources for the purpose of displaying the generated events.
The following resources need to be created:
- 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 Timer CamelSource
The samples directory contains some sample sources that can be used to generate events.
The simplest example of CamelSource
, that does not require additional
configuration, is the timer source.
The timer source periodically generates “Hello world!” events and forwards them to the provided destination.
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 Website.
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
If you have deployed the timer source, you should see new log lines appearing every 3 seconds.
Run a MQTT CamelSource
One of the 300+ Camel components that you can leverage is Camel-Paho, based on the Eclipse Paho open source project.
A source based on Paho (like the provided MQTT CamelSource) allows to bridge any MQTT broker to a Knative resource, automatically converting IoT messages to Cloudevents.
To use the MQTT source, you need a MQTT broker running and reachable from your cluster. For example, it’s possible to run a Mosquito MQTT Broker for testing purposes.
First, edit the MQTT CamelSource and put the
correct address of the MQTT broker in the brokerUrl
field.
You also need to provide the name of the topic that you want to subscribe to: just change paho:mytopic
to match
the topic that you want to use.
You can also scale this source out, in order to obtain more throughput, by changing the value of the replicas
field.
By default it creates 2 replicas for demonstration purposes.
To reduce noise in the event display, you can remove all previously created CamelSources from the namespace:
kubectl delete camelsource --all
Install the mqtt CamelSource:
kubectl apply -f source_mqtt.yaml
You can now send MQTT messages to your broker using your favourite client (you can even use Camel K for sending test events).
Each message you send to the MQTT broker will be printed by the event display as a Cloudevent.
You can verify that your messages reach the event display by checking its logs:
kubectl logs --selector serving.knative.dev/service=camel-event-display -c user-container
Run a Telegram CamelSource
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 all previously created CamelSources from the namespace:
kubectl delete camelsource --all
Install the telegram CamelSource:
kubectl apply -f source_telegram.yaml
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.
You can verify that your messages reach the event display by checking its logs:
kubectl logs --selector serving.knative.dev/service=camel-event-display -c user-container
Run an HTTP Poller CamelSource
CamelSources are not limited to using a single Camel component. For example, you can combine the Camel Timer component with the Camel HTTP component to periodically fetch an external API, transform the result into a Cloudevent and forward it to a given destination.
The example will retrieve a static JSON file from a remote URL, but you can edit the HTTP poller CamelSource to add your own API.
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 HTTP poller CamelSource:
kubectl apply -f source_http_poller.yaml
The event display will show some JSON data periodically pulled from the external REST API. To check the logs:
kubectl logs --selector serving.knative.dev/service=camel-event-display -c user-container
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