Knative

Since Camel 3.15

Both producer and consumer are supported

The Knative component provides support for interacting with Knative.

Maven users will need to add the following dependency to their pom.xml for this component.

<dependency>
    <groupId>org.apache.camel</groupId>
    <artifactId>camel-knative</artifactId>
    <version>x.x.x</version>
    <!-- use the same version as your Camel K version -->
</dependency>

URI format

knative:type/name[?options]

You can append query options to the URI in the following format:

?option=value&option=value&...

Options

Configuring Options

Camel components are configured on two separate levels:

  • component level

  • endpoint level

Configuring Component Options

The component level is the highest level which holds general and common configurations that are inherited by the endpoints. For example a component may have security settings, credentials for authentication, urls for network connection and so forth.

Some components only have a few options, and others may have many. Because components typically have pre configured defaults that are commonly used, then you may often only need to configure a few options on a component; or none at all.

Configuring components can be done with the Component DSL, in a configuration file (application.properties|yaml), or directly with Java code.

Configuring Endpoint Options

Where you find yourself configuring the most is on endpoints, as endpoints often have many options, which allows you to configure what you need the endpoint to do. The options are also categorized into whether the endpoint is used as consumer (from) or as a producer (to), or used for both.

Configuring endpoints is most often done directly in the endpoint URI as path and query parameters. You can also use the Endpoint DSL as a type safe way of configuring endpoints.

A good practice when configuring options is to use Property Placeholders, which allows to not hardcode urls, port numbers, sensitive information, and other settings. In other words placeholders allows to externalize the configuration from your code, and gives more flexibility and reuse.

The following two sections lists all the options, firstly for the component followed by the endpoint.

Component Options

The Knative component supports 19 options, which are listed below.

Name Description Default Type

ceOverride (common)

CloudEvent headers to override.

Map

cloudEventsSpecVersion (common)

Set the version of the cloudevents spec.

Enum values:

  • 1.0

  • 1.0.1

1.0

String

cloudEventsType (common)

Set the event-type information of the produced events.

org.apache.camel.event

String

configuration (common)

Set the configuration.

KnativeConfiguration

consumerFactory (common)

The protocol consumer factory.

KnativeConsumerFactory

environment (common)

The environment.

KnativeEnvironment

environmentPath (common)

The path ot the environment definition.

String

filters (common)

Set the filters.

Map

producerFactory (common)

The protocol producer factory.

KnativeProducerFactory

transportOptions (common)

Set the transport options.

Map

typeId (common)

The name of the service to lookup from the KnativeEnvironment.

String

bridgeErrorHandler (consumer)

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

replyWithCloudEvent (consumer)

Transforms the reply into a cloud event that will be processed by the caller. When listening to events from a Knative Broker, if this flag is enabled, replies will be published to the same Broker where the request comes from (beware that if you don’t change the type of the received message, you may create a loop and receive your same reply). When this flag is disabled, CloudEvent headers are removed from the reply.

false

boolean

reply (consumer (advanced))

If the consumer should construct a full reply to knative request.

true

Boolean

lazyStartProducer (producer)

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

apiVersion (advanced)

The version of the k8s resource referenced by the endpoint.

String

autowiredEnabled (advanced)

Whether autowiring is enabled. This is used for automatic autowiring options (the option must be marked as autowired) by looking up in the registry to find if there is a single instance of matching type, which then gets configured on the component. This can be used for automatic configuring JDBC data sources, JMS connection factories, AWS Clients, etc.

true

boolean

kind (advanced)

The type of the k8s resource referenced by the endpoint.

String

name (advanced)

The name of the k8s resource referenced by the endpoint.

String

Endpoint Options

The Knative endpoint is configured using URI syntax:

knative:type/typeId

with the following path and query parameters:

Path Parameters (2 parameters)

Name Description Default Type

type (common)

The Knative resource type.

Enum values:

  • endpoint

  • channel

  • event

Type

typeId (common)

The identifier of the Knative resource.

String

Query Parameters (15 parameters)

Name Description Default Type

ceOverride (common)

CloudEvent headers to override.

Map

cloudEventsSpecVersion (common)

Set the version of the cloudevents spec.

Enum values:

  • 1.0

  • 1.0.1

1.0

String

cloudEventsType (common)

Set the event-type information of the produced events.

org.apache.camel.event

String

environment (common)

The environment.

KnativeEnvironment

filters (common)

Set the filters.

Map

transportOptions (common)

Set the transport options.

Map

replyWithCloudEvent (consumer)

Transforms the reply into a cloud event that will be processed by the caller. When listening to events from a Knative Broker, if this flag is enabled, replies will be published to the same Broker where the request comes from (beware that if you don’t change the type of the received message, you may create a loop and receive your same reply). When this flag is disabled, CloudEvent headers are removed from the reply.

false

boolean

bridgeErrorHandler (consumer (advanced))

Allows for bridging the consumer to the Camel routing Error Handler, which mean any exceptions occurred while the consumer is trying to pickup incoming messages, or the likes, will now be processed as a message and handled by the routing Error Handler. By default the consumer will use the org.apache.camel.spi.ExceptionHandler to deal with exceptions, that will be logged at WARN or ERROR level and ignored.

false

boolean

exceptionHandler (consumer (advanced))

To let the consumer use a custom ExceptionHandler. Notice if the option bridgeErrorHandler is enabled then this option is not in use. By default the consumer will deal with exceptions, that will be logged at WARN or ERROR level and ignored.

ExceptionHandler

exchangePattern (consumer (advanced))

Sets the exchange pattern when the consumer creates an exchange.

Enum values:

  • InOnly

  • InOut

  • InOptionalOut

ExchangePattern

reply (consumer (advanced))

If the consumer should construct a full reply to knative request.

true

Boolean

lazyStartProducer (producer (advanced))

Whether the producer should be started lazy (on the first message). By starting lazy you can use this to allow CamelContext and routes to startup in situations where a producer may otherwise fail during starting and cause the route to fail being started. By deferring this startup to be lazy then the startup failure can be handled during routing messages via Camel’s routing error handlers. Beware that when the first message is processed then creating and starting the producer may take a little time and prolong the total processing time of the processing.

false

boolean

apiVersion (advanced)

The version of the k8s resource referenced by the endpoint.

String

kind (advanced)

The type of the k8s resource referenced by the endpoint.

String

name (advanced)

The name of the k8s resource referenced by the endpoint.

String

Supported Knative resources

The component support the following Knative resources you can target or exposes using the type path parameter:

  • channel allow producing or consuming events to or from a Knative Channel

  • endpoint allow exposing or targeting serverless workloads using Knative Services

  • event allow producing or consuming events to or from a Knative Broker

Knative Environment

As the Knative component hides the technical details of how to communicate with Knative services to the user (protocols, addresses, etc.), it needs some metadata that describe the Knative environment to set-up the low level transport details. In order to do so, the component needs a so called Knative Environment which is essence is a Json document made by a number of service elements which looks like the below example:

{
    "services": [
        {
             "type": "channel|endpoint|event", (1)
             "name": "", (2)
             "metadata": {
                 "service.url": "http://my-service.svc.cluster.local" (3)
                 "knative.event.type": "", (4)
                 "camel.endpoint.kind": "source|sink", (5)
             }
        }, {
            ...
        }
    ]
}
1 the type of the Knative resource
2 the name of the resource
3 the url of the service to invoke (for producer only)
4 the Knative event type received or produced by the component
5 the type of the Camel Endpoint associated to this Knative resource (source=consumer, sink=producer)

The metadata fields has some additional advanced fields:

Name Description Example

filter.

The prefix to define filters to be applied to the incoming message headers.

filter.ce.source=my-source

knative.kind

The type of the k8s resource referenced by the endpoint.

knative.kind=InMemoryChannel

knative.apiVersion

The version of the k8s resource referenced by the endpoint

knative.apiVersion=messaging.knative.dev/v1beta1

knative.reply

If the consumer should construct a full reply to knative request.

knative.reply=false

ce.override.

The prefix to define CloudEvents values that have to be overridden.

ce.override.ce-type=MyType

Example

CamelContext context = new DefaultCamelContext();

KnativeComponent component = context.getComponent("knative", KnativeComponent.class);
component.getConfiguration().setEnvironmentPath("classpath:knative.json"); (1)

RouteBuilder.addRoutes(context, b -> {
    b.from("knative:endpoint/myEndpoint") (2)
        .to("log:info");
});
1 set the location of the Knative Environment file
2 expose knative service

Using custom Knative Transport

As today the component only support http as transport as it is the only supported protocol on Knative side but the transport is pluggable by implementing the following interface:

public interface KnativeTransport extends Service {
    /**
     * Create a camel {@link org.apache.camel.Producer} in place of the original endpoint for a specific protocol.
     *
     * @param endpoint the endpoint for which the producer should be created
     * @param configuration the general transport configuration
     * @param service the service definition containing information about how make reach the target service.
     */
    Producer createProducer(
        Endpoint endpoint,
        KnativeTransportConfiguration configuration,
        KnativeEnvironment.KnativeServiceDefinition service);

    /**
     * Create a camel {@link org.apache.camel.Producer} in place of the original endpoint for a specific protocol.
     *
     * @param endpoint the endpoint for which the consumer should be created.
     * @param configuration the general transport configuration
     * @param service the service definition containing information about how make the route reachable from knative.
     */
    Consumer createConsumer(
        Endpoint endpoint,
        KnativeTransportConfiguration configuration,
        KnativeEnvironment.KnativeServiceDefinition service, Processor processor);
}
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