Red Hat SummitChapter 36. Flink
Since Camel 2.18
Only producer is supported
This documentation page covers the Flink component for the Apache Camel. The camel-flink component provides a bridge between Camel components and Flink tasks. This component provides a way to route a message from various transports, dynamically choosing a flink task to execute, use an incoming message as input data for the task and finally deliver the results back to the Camel pipeline.
36.1. Dependencies
When using camel-flink with Red Hat build of Camel Spring Boot, add the following Maven dependency to your pom.xml to have support for auto configuration:
Maven users will need to add the following dependency to their pom.xml for this component:
<dependency>
<groupId>org.apache.camel.springboot</groupId>
<artifactId>camel-flink-starter</artifactId>
</dependency>36.2. URI Format
Currently, the Flink Component supports only Producers. One can create DataSet, DataStream jobs.
flink:dataset?dataset=#myDataSet&dataSetCallback=#dataSetCallback
flink:datastream?datastream=#myDataStream&dataStreamCallback=#dataStreamCallback36.3. Configuring Options
Camel components are configured on two levels:
- Component level
- Endpoint level
36.3.1. Component Level Options
The component level is the highest level. The configurations you define at this level are inherited by all the endpoints. For example, a component can have security settings, credentials for authentication, urls for network connection, and so on.
Since components typically have pre-configured defaults for the most common cases, you may need to only configure a few component options, or maybe none at all.
You can configure components with Component DSL in a configuration file (application.properties|yaml), or directly with Java code.
36.3.2. Endpoint Level Options
At the Endpoint level you have many options, which you can use to configure what you want the endpoint to do. The options are categorized according to whether the endpoint is used as a consumer (from) or as a producer (to) or used for both.
You can configure endpoints directly in the endpoint URI as path and query parameters. You can also use Endpoint DSL and DataFormat DSL as type safe ways of configuring endpoints and data formats in Java.
When configuring options, use Property Placeholders for urls, port numbers, sensitive information, and other settings.
Placeholders allows you to externalize the configuration from your code, giving you more flexible and reusable code.
36.4. Component Options
The Flink component supports 5 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| dataSetCallback (producer) | Function performing action against a DataSet. | DataSetCallback | |
| dataStream (producer) | DataStream to compute against. | DataStream | |
| dataStreamCallback (producer) | Function performing action against a DataStream. | DataStreamCallback | |
| 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 |
| 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 |
36.5. Endpoint Options
The Flink endpoint is configured using URI syntax:
flink:endpointTypeWith the following path and query parameters:
36.5.1. Path Parameters (1 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| endpointType (producer) | Required Type of the endpoint (dataset, datastream). Enum values:
| EndpointType |
36.5.2. Query Parameters (6 parameters)
| Name | Description | Default | Type |
|---|---|---|---|
| collect (producer) | Indicates if results should be collected or counted. | true | boolean |
| dataSet (producer) | DataSet to compute against. | DataSet | |
| dataSetCallback (producer) | Function performing action against a DataSet. | DataSetCallback | |
| dataStream (producer) | DataStream to compute against. | DataStream | |
| dataStreamCallback (producer) | Function performing action against a DataStream. | DataStreamCallback | |
| 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 |
36.6. Message Headers
The Flink component supports 4 message header(s), which is/are listed below:
| Name | Description | Default | Type |
|---|---|---|---|
| CamelFlinkDataSet (producer) Constant: FLINK_DATASET_HEADER | The dataset. | Object | |
| CamelFlinkDataSetCallback (producer) Constant: FLINK_DATASET_CALLBACK_HEADER | The dataset callback. | DataSetCallback | |
| CamelFlinkDataStream (producer) Constant:FLINK_DATASTREAM_HEADER | The data stream. | Object | |
| CamelFlinkDataStreamCallback (producer) Constant:FLINK_DATASTREAM_CALLBACK_HEADER | The data stream callback. | DataStreamCallback |
36.7. Flink DataSet Callback
@Bean
public DataSetCallback<Long> dataSetCallback() {
return new DataSetCallback<Long>() {
public Long onDataSet(DataSet dataSet, Object... objects) {
try {
dataSet.print();
return new Long(0);
} catch (Exception e) {
return new Long(-1);
}
}
};
}36.8. Flink DataStream Callback
@Bean
public VoidDataStreamCallback dataStreamCallback() {
return new VoidDataStreamCallback() {
@Override
public void doOnDataStream(DataStream dataStream, Object... objects) throws Exception {
dataStream.flatMap(new Splitter()).print();
environment.execute("data stream test");
}
};
}36.9. Camel-Flink Producer call
CamelContext camelContext = new SpringCamelContext(context);
String pattern = "foo";
try {
ProducerTemplate template = camelContext.createProducerTemplate();
camelContext.start();
Long count = template.requestBody("flink:dataSet?dataSet=#myDataSet&dataSetCallback=#countLinesContaining", pattern, Long.class);
} finally {
camelContext.stop();
}36.10. Spring Boot Auto-Configuration
The component supports 6 options, which are listed below.
| Name | Description | Default | Type |
|---|---|---|---|
| camel.component.flink.autowired-enabled | 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 |
| camel.component.flink.data-set-callback | Function performing action against a DataSet. The option is a org.apache.camel.component.flink.DataSetCallback type. | DataSetCallback | |
| camel.component.flink.data-stream | DataStream to compute against. The option is a org.apache.flink.streaming.api.datastream.DataStream type. | DataStream | |
| camel.component.flink.data-stream-callback | Function performing action against a DataStream. The option is a org.apache.camel.component.flink.DataStreamCallback type. | DataStreamCallback | |
| camel.component.flink.enabled | Whether to enable auto configuration of the flink component. This is enabled by default. | Boolean | |
| camel.component.flink.lazy-start-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 |
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