Apache Spark

Since Camel 2.17

This documentation page covers the Apache Spark component for the Apache Camel. The main purpose of the Spark integration with Camel is to provide a bridge between Camel connectors and Spark tasks. In particular Camel connector provides a way to route message from various transports, dynamically choose a task to execute, use incoming message as input data for that task and finally deliver the results of the execution back to the Camel pipeline.

Supported architectural styles

Spark component can be used as a driver application deployed into an application server (or executed as a fat jar).

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Spark component can also be submitted as a job directly into the Spark cluster.

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While Spark component is primary designed to work as a long running job serving as an bridge between Spark cluster and the other endpoints, you can also use it as a fire-once short job.

Running Spark in OSGi servers

Currently the Spark component doesn’t support execution in the OSGi container. Spark has been designed to be executed as a fat jar, usually submitted as a job to a cluster. For those reasons running Spark in an OSGi server is at least challenging and is not support by Camel as well.

URI format

Currently the Spark component supports only producers - it it intended to invoke a Spark job and return results. You can call RDD, data frame or Hive SQL job.

Spark URI format

spark:{rdd|dataframe|hive}

Spark options

The Apache Spark component supports 3 options, which are listed below.

Name Description Default Type

rdd (producer)

RDD to compute against.

JavaRDDLike

rddCallback (producer)

Function performing action against an RDD.

RddCallback

resolveProperty Placeholders (advanced)

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

boolean

The Apache Spark endpoint is configured using URI syntax:

spark:endpointType

with the following path and query parameters:

Path Parameters (1 parameters):

Name Description Default Type

endpointType

Required Type of the endpoint (rdd, dataframe, hive).

EndpointType

Query Parameters (6 parameters):

Name Description Default Type

collect (producer)

Indicates if results should be collected or counted.

true

boolean

dataFrame (producer)

DataFrame to compute against.

Dataset

dataFrameCallback (producer)

Function performing action against an DataFrame.

DataFrameCallback

rdd (producer)

RDD to compute against.

JavaRDDLike

rddCallback (producer)

Function performing action against an RDD.

RddCallback

synchronous (advanced)

Sets whether synchronous processing should be strictly used, or Camel is allowed to use asynchronous processing (if supported).

false

boolean

Spring Boot Auto-Configuration

When using Spring Boot make sure to use the following Maven dependency to have support for auto configuration:

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

The component supports 4 options, which are listed below.

Name Description Default Type

camel.component.spark.enabled

Enable spark component

true

Boolean

camel.component.spark.rdd

RDD to compute against. The option is a org.apache.spark.api.java.JavaRDDLike type.

String

camel.component.spark.rdd-callback

Function performing action against an RDD. The option is a org.apache.camel.component.spark.RddCallback type.

String

camel.component.spark.resolve-property-placeholders

Whether the component should resolve property placeholders on itself when starting. Only properties which are of String type can use property placeholders.

true

Boolean

RDD jobs

To invoke an RDD job, use the following URI:

Spark RDD producer

spark:rdd?rdd=#testFileRdd&rddCallback=#transformation

 Where rdd option refers to the name of an RDD instance (subclass of org.apache.spark.api.java.JavaRDDLike) from a Camel registry, while rddCallback refers to the implementation of org.apache.camel.component.spark.RddCallback interface (also from a registry). RDD callback provides a single method used to apply incoming messages against the given RDD. Results of callback computations are saved as a body to an exchange.

Spark RDD callback

public interface RddCallback<T> {
    T onRdd(JavaRDDLike rdd, Object... payloads);
}

The following snippet demonstrates how to send message as an input to the job and return results:

Calling spark job

String pattern = "job input";
long linesCount = producerTemplate.requestBody("spark:rdd?rdd=#myRdd&rddCallback=#countLinesContaining", pattern, long.class);

The RDD callback for the snippet above registered as Spring bean could look as follows:

Spark RDD callback

@Bean
RddCallback<Long> countLinesContaining() {
    return new RddCallback<Long>() {
        Long onRdd(JavaRDDLike rdd, Object... payloads) {
            String pattern = (String) payloads[0];
            return rdd.filter({line -> line.contains(pattern)}).count();
        }
    }
}

The RDD definition in Spring could looks as follows:

Spark RDD definition

@Bean
JavaRDDLike myRdd(JavaSparkContext sparkContext) {
  return sparkContext.textFile("testrdd.txt");
}

Void RDD callbacks

If your RDD callback doesn’t return any value back to a Camel pipeline, you can either return null value or use VoidRddCallback base class:

Spark RDD definition

@Bean
RddCallback<Void> rddCallback() {
  return new VoidRddCallback() {
        @Override
        public void doOnRdd(JavaRDDLike rdd, Object... payloads) {
            rdd.saveAsTextFile(output.getAbsolutePath());
        }
    };
}

Converting RDD callbacks

If you know what type of the input data will be sent to the RDD callback, you can use ConvertingRddCallback and let Camel to automatically convert incoming messages before inserting those into the callback:

Spark RDD definition

@Bean
RddCallback<Long> rddCallback(CamelContext context) {
  return new ConvertingRddCallback<Long>(context, int.class, int.class) {
            @Override
            public Long doOnRdd(JavaRDDLike rdd, Object... payloads) {
                return rdd.count() * (int) payloads[0] * (int) payloads[1];
            }
        };
    };
}

Annotated RDD callbacks

Probably the easiest way to work with the RDD callbacks is to provide class with method marked with @RddCallback annotation:

Annotated RDD callback definition

import static org.apache.camel.component.spark.annotations.AnnotatedRddCallback.annotatedRddCallback;

@Bean
RddCallback<Long> rddCallback() {
    return annotatedRddCallback(new MyTransformation());
}

...

import org.apache.camel.component.spark.annotation.RddCallback;

public class MyTransformation {

    @RddCallback
    long countLines(JavaRDD<String> textFile, int first, int second) {
        return textFile.count() * first * second;
    }

}

If you will pass CamelContext to the annotated RDD callback factory method, the created callback will be able to convert incoming payloads to match the parameters of the annotated method:

Body conversions for annotated RDD callbacks

import static org.apache.camel.component.spark.annotations.AnnotatedRddCallback.annotatedRddCallback;

@Bean
RddCallback<Long> rddCallback(CamelContext camelContext) {
    return annotatedRddCallback(new MyTransformation(), camelContext);
}

...


import org.apache.camel.component.spark.annotation.RddCallback;

public class MyTransformation {

    @RddCallback
    long countLines(JavaRDD<String> textFile, int first, int second) {
        return textFile.count() * first * second;
    }

}

...

// Convert String "10" to integer
long result = producerTemplate.requestBody("spark:rdd?rdd=#rdd&rddCallback=#rddCallback" Arrays.asList(10, "10"), long.class);

DataFrame jobs

Instead of working with RDDs Spark component can work with DataFrames as well.

To invoke an DataFrame job, use the following URI:

Spark RDD producer

spark:dataframe?dataFrame=#testDataFrame&dataFrameCallback=#transformation

 Where dataFrame option refers to the name of an DataFrame instance (instances of org.apache.spark.sql.Dataset and org.apache.spark.sql.Row) from a Camel registry, while dataFrameCallback refers to the implementation of org.apache.camel.component.spark.DataFrameCallback interface (also from a registry). DataFrame callback provides a single method used to apply incoming messages against the given DataFrame. Results of callback computations are saved as a body to an exchange.

Spark RDD callback

public interface DataFrameCallback<T> {
    T onDataFrame(Dataset<Row> dataFrame, Object... payloads);
}

The following snippet demonstrates how to send message as an input to a job and return results:

Calling spark job

String model = "Micra";
long linesCount = producerTemplate.requestBody("spark:dataFrame?dataFrame=#cars&dataFrameCallback=#findCarWithModel", model, long.class);

The DataFrame callback for the snippet above registered as Spring bean could look as follows:

Spark RDD callback

@Bean
RddCallback<Long> findCarWithModel() {
    return new DataFrameCallback<Long>() {
        @Override
        public Long onDataFrame(Dataset<Row> dataFrame, Object... payloads) {
            String model = (String) payloads[0];
            return dataFrame.where(dataFrame.col("model").eqNullSafe(model)).count();
        }
    };
}

The DataFrame definition in Spring could looks as follows:

Spark RDD definition

@Bean
Dataset<Row> cars(HiveContext hiveContext) {
    Dataset<Row> jsonCars = hiveContext.read().json("/var/data/cars.json");
    jsonCars.registerTempTable("cars");
    return jsonCars;
}

Hive jobs

 Instead of working with RDDs or DataFrame Spark component can also receive Hive SQL queries as payloads. To send Hive query to Spark component, use the following URI:

Spark RDD producer

spark:hive

The following snippet demonstrates how to send message as an input to a job and return results:

Calling spark job

long carsCount = template.requestBody("spark:hive?collect=false", "SELECT * FROM cars", Long.class);
List<Row> cars = template.requestBody("spark:hive", "SELECT * FROM cars", List.class);

The table we want to execute query against should be registered in a HiveContext before we query it. For example in Spring such registration could look as follows:

Spark RDD definition

@Bean
Dataset<Row> cars(HiveContext hiveContext) {
     jsonCars = hiveContext.read().json("/var/data/cars.json");
    jsonCars.registerTempTable("cars");
    return jsonCars;
}
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