---
title: Spark (Scala)
description: Build a Scala Spark application that connects to R2 Data Catalog for Iceberg table operations.
image: https://developers.cloudflare.com/dev-products-preview.png
---

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# Spark (Scala)

**Last reviewed:**  about 1 year ago 

Below is an example of how you can build an [Apache Spark ↗](https://spark.apache.org/) application (with Scala) which connects to R2 Data Catalog. This application is built to run locally, but it can be adapted to run on a cluster.

## Prerequisites

* Sign up for a [Cloudflare account ↗](https://dash.cloudflare.com/sign-up/workers-and-pages).
* [Create an R2 bucket](https://developers.cloudflare.com/r2/buckets/create-buckets/) and [enable the data catalog](https://developers.cloudflare.com/r2/data-catalog/manage-catalogs/#enable-r2-data-catalog-on-a-bucket).
* [Create an R2 API token](https://developers.cloudflare.com/r2/api/tokens/) with both [R2 and data catalog permissions](https://developers.cloudflare.com/r2/api/tokens/#permissions).
* Install Java 17, Spark 3.5.3, and SBT 1.10.11  
   * Note: The specific versions of tools are critical for getting things to work in this example.  
   * Tip: [“SDKMAN” ↗](https://sdkman.io/) is a convenient package manager for installing SDKs.

## Example usage

To start, create a new empty project directory somewhere on your machine.

Inside that directory, create the following file at `src/main/scala/com/example/R2DataCatalogDemo.scala`. This will serve as the main entry point for your Spark application.

```

package com.example


import org.apache.spark.sql.SparkSession


object R2DataCatalogDemo {

    def main(args: Array[String]): Unit = {


        val uri = sys.env("CATALOG_URI")

        val warehouse = sys.env("WAREHOUSE")

        val token = sys.env("TOKEN")


        val spark = SparkSession.builder()

            .appName("My R2 Data Catalog Demo")

            .master("local[*]")

            .config("spark.sql.extensions", "org.apache.iceberg.spark.extensions.IcebergSparkSessionExtensions")

            .config("spark.sql.catalog.mydemo", "org.apache.iceberg.spark.SparkCatalog")

            .config("spark.sql.catalog.mydemo.type", "rest")

            .config("spark.sql.catalog.mydemo.uri", uri)

            .config("spark.sql.catalog.mydemo.warehouse", warehouse)

            .config("spark.sql.catalog.mydemo.token", token)

            .getOrCreate()


        import spark.implicits._


        val data = Seq(

            (1, "Alice", 25),

            (2, "Bob", 30),

            (3, "Charlie", 35),

            (4, "Diana", 40)

        ).toDF("id", "name", "age")


        spark.sql("USE mydemo")


        spark.sql("CREATE NAMESPACE IF NOT EXISTS demoNamespace")


        data.writeTo("demoNamespace.demotable").createOrReplace()


        val readResult = spark.sql("SELECT * FROM demoNamespace.demotable WHERE age > 30")

        println("Records with age > 30:")

        readResult.show()

    }

}


```

For building this application and managing dependencies, we will use [sbt (“simple build tool”) ↗](https://www.scala-sbt.org/). The following is an example `build.sbt` file to place at the root of your project. It is configured to produce a "fat JAR", bundling all required dependencies.

```

name := "R2DataCatalogDemo"


version := "1.0"


val sparkVersion = "3.5.3"

val icebergVersion = "1.8.1"


// You need to use binaries of Spark compiled with either 2.12 or 2.13; and 2.12 is more common.

// If you download Spark 3.5.3 with sdkman, then it comes with 2.12.18

scalaVersion := "2.12.18"


libraryDependencies ++= Seq(

    "org.apache.spark" %% "spark-core" % sparkVersion,

    "org.apache.spark" %% "spark-sql" % sparkVersion,

    "org.apache.iceberg" % "iceberg-core" % icebergVersion,

    "org.apache.iceberg" % "iceberg-spark-runtime-3.5_2.12" % icebergVersion,

    "org.apache.iceberg" % "iceberg-aws-bundle" % icebergVersion,

)


// build a fat JAR with all dependencies

assembly / assemblyMergeStrategy := {

    case PathList("META-INF", "services", xs @ _*) => MergeStrategy.concat

    case PathList("META-INF", xs @ _*) => MergeStrategy.discard

    case "reference.conf" => MergeStrategy.concat

    case "application.conf" => MergeStrategy.concat

    case x if x.endsWith(".properties") => MergeStrategy.first

    case x => MergeStrategy.first

}


// For Java  17 Compatability

Compile / javacOptions ++= Seq("--release", "17")


```

To enable the [sbt-assembly plugin ↗](https://github.com/sbt/sbt-assembly?tab=readme-ov-file) (used to build fat JARs), add the following to a new file at `project/assembly.sbt`:

```

addSbtPlugin("com.eed3si9n" % "sbt-assembly" % "1.2.0")


```

Make sure Java, Spark, and sbt are installed and available in your shell. If you are using SDKMAN, you can install them as shown below:

Terminal window

```

sdk install java 17.0.14-amzn

sdk install spark 3.5.3

sdk install sbt 1.10.11


```

With everything installed, you can now build the project using sbt. This will generate a single bundled JAR file.

Terminal window

```

sbt clean assembly


```

After building, the output JAR should be located at `target/scala-2.12/R2DataCatalogDemo-assembly-1.0.jar`.

To run the application, you will use `spark-submit`. Below is an example shell script (`submit.sh`) that includes the necessary Java compatibility flags for Spark on Java 17:

```

# We need to set these "--add-opens" so that Spark can run on Java 17 (it needs access to

# parts of the JVM which have been modularized and made internal).

JAVA_17_COMPATABILITY="--add-opens=java.base/sun.nio.ch=ALL-UNNAMED --add-opens=java.base/java.nio=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED"


spark-submit \

--conf "spark.driver.extraJavaOptions=$JAVA_17_COMPATABILITY" \

--conf "spark.executor.extraJavaOptions=$JAVA_17_COMPATABILITY" \

--class com.example.R2DataCatalogDemo target/scala-2.12/R2DataCatalogDemo-assembly-1.0.jar


```

Before running it, make sure the script is executable:

Terminal window

```

chmod +x submit.sh


```

At this point, your project directory should be structured like this:

* Makefile
* README.md
* build.sbt
* Directoryproject  
   * assembly.sbt  
   * build.properties  
   * project
* spark-submit.sh
* Directorysrc  
   * Directorymain  
         * Directoryscala  
                  * Directorycom  
                              * Directoryexample  
                                             * R2DataCatalogDemo.scala

Before submitting the job, make sure you have the required environment variable set for your catalog URI, warehouse, and [Cloudflare API token](https://developers.cloudflare.com/r2/api/tokens/).

Terminal window

```

export CATALOG_URI=

export WAREHOUSE=

export TOKEN=


```

You are now ready to run the job:

Terminal window

```

./submit.sh


```

```json
{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/directory/","name":"Directory"}},{"@type":"ListItem","position":2,"item":{"@id":"/r2/","name":"R2"}},{"@type":"ListItem","position":3,"item":{"@id":"/r2/data-catalog/","name":"R2 Data Catalog"}},{"@type":"ListItem","position":4,"item":{"@id":"/r2/data-catalog/config-examples/","name":"Connect to Iceberg engines"}},{"@type":"ListItem","position":5,"item":{"@id":"/r2/data-catalog/config-examples/spark-scala/","name":"Spark (Scala)"}}]}
```