Apache Kudu

The Alpakka Kudu connector supports writing to Apache Kudu tables.

Apache Kudu is a free and open source column-oriented data store in the Apache Hadoop ecosystem.

Artifacts

The Akka dependencies are available from Akka’s library repository. To access them there, you need to configure the URL for this repository.

sbt

resolvers += "Akka library repository".at("https://repo.akka.io/maven")

Maven

<project>
  ...
  <repositories>
    <repository>
      <id>akka-repository</id>
      <name>Akka library repository</name>
      <url>https://repo.akka.io/maven</url>
    </repository>
  </repositories>
</project>

Gradle

repositories {
    mavenCentral()
    maven {
        url "https://repo.akka.io/maven"
    }
}

Additionally, add the dependencies as below.

sbt

val AkkaVersion = "2.10.0"
libraryDependencies ++= Seq(
  "com.lightbend.akka" %% "akka-stream-alpakka-kudu" % "9.0.0",
  "com.typesafe.akka" %% "akka-stream" % AkkaVersion
)

Maven

<properties>
  <akka.version>2.10.0</akka.version>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencies>
  <dependency>
    <groupId>com.lightbend.akka</groupId>
    <artifactId>akka-stream-alpakka-kudu_${scala.binary.version}</artifactId>
    <version>9.0.0</version>
  </dependency>
  <dependency>
    <groupId>com.typesafe.akka</groupId>
    <artifactId>akka-stream_${scala.binary.version}</artifactId>
    <version>${akka.version}</version>
  </dependency>
</dependencies>

Gradle

def versions = [
  AkkaVersion: "2.10.0",
  ScalaBinary: "2.13"
]
dependencies {
  implementation "com.lightbend.akka:akka-stream-alpakka-kudu_${versions.ScalaBinary}:9.0.0"
  implementation "com.typesafe.akka:akka-stream_${versions.ScalaBinary}:${versions.AkkaVersion}"
}

The table below shows direct dependencies of this module and the second tab shows all libraries it depends on transitively.

Direct dependencies

Organization	Artifact	Version
com.typesafe.akka	akka-stream_2.13	2.10.0
org.apache.kudu	kudu-client-tools	1.7.1
org.scala-lang	scala-library	2.13.12

Dependency tree

com.typesafe.akka    akka-stream_2.13    2.10.0    BUSL-1.1
    com.typesafe.akka    akka-actor_2.13    2.10.0    BUSL-1.1
        com.typesafe    config    1.4.3    Apache-2.0
        org.scala-lang    scala-library    2.13.12    Apache-2.0
    com.typesafe.akka    akka-protobuf-v3_2.13    2.10.0    BUSL-1.1
    org.reactivestreams    reactive-streams    1.0.4    MIT-0
    org.scala-lang    scala-library    2.13.12    Apache-2.0
org.apache.kudu    kudu-client-tools    1.7.1
    org.slf4j    slf4j-api    1.7.25
org.scala-lang    scala-library    2.13.12    Apache-2.0

Configuration

To connect to Kudu you need:

1. Describe the Kudu Schema
2. Define a converter function to map your data type to a PartialRow
3. Specify Kudu CreateTableOptions
4. Set up Alpakka’s KuduTableSettings

Scala

copysource// Kudu Schema
val cols = List(new ColumnSchema.ColumnSchemaBuilder("key", Type.INT32).key(true).build,
                new ColumnSchema.ColumnSchemaBuilder("value", Type.STRING).build)
val schema = new Schema(cols.asJava)

// Converter function
case class Person(id: Int, name: String)
val kuduConverter: Person => PartialRow = { person =>
  val partialRow = schema.newPartialRow()
  partialRow.addInt(0, person.id)
  partialRow.addString(1, person.name)
  partialRow
}

// Kudu table options
val rangeKeys = List("key")
val createTableOptions = new CreateTableOptions().setNumReplicas(1).setRangePartitionColumns(rangeKeys.asJava)

// Alpakka settings
val kuduTableSettings = KuduTableSettings("test", schema, createTableOptions, kuduConverter)

Java

copysource// Kudu Schema
List<ColumnSchema> columns = new ArrayList<>(2);
columns.add(new ColumnSchema.ColumnSchemaBuilder("key", Type.INT32).key(true).build());
columns.add(new ColumnSchema.ColumnSchemaBuilder("value", Type.STRING).build());
schema = new Schema(columns);

// Converter function
Function<Person, PartialRow> kuduConverter =
    person -> {
      PartialRow partialRow = schema.newPartialRow();
      partialRow.addInt(0, person.id);
      partialRow.addString(1, person.name);
      return partialRow;
    };

// Kudu table options
List<String> rangeKeys = Collections.singletonList("key");
CreateTableOptions createTableOptions =
    new CreateTableOptions().setNumReplicas(1).setRangePartitionColumns(rangeKeys);

// Alpakka settings
KuduTableSettings<Person> tableSettings =
    KuduTableSettings.create("tablenameSink", schema, createTableOptions, kuduConverter);

The KuduClient by default is automatically managed by the connector. Settings for the client are read from the reference.conf file. A manually initialized client can be injected to the stream using KuduAttributes

Scala

copysourceval masterAddress = "localhost:7051"
val client = new KuduClient.KuduClientBuilder(masterAddress).build
system.registerOnTermination(client.shutdown())

val flow: Flow[Person, Person, NotUsed] =
  KuduTable
    .flow(kuduTableSettings.withTableName("Flow"))
    .withAttributes(KuduAttributes.client(client))

Java

copysourcefinal String masterAddress = "localhost:7051";
final KuduClient client = new KuduClient.KuduClientBuilder(masterAddress).build();
system.registerOnTermination(
    () -> {
      try {
        client.shutdown();
      } catch (KuduException e) {
        e.printStackTrace();
      }
    });

final Flow<Person, Person, NotUsed> flow =
    KuduTable.flow(tableSettings.withTableName("Flow"))
        .withAttributes(KuduAttributes.client(client));

Writing to Kudu in a Flow

Scala

copysourceval flow: Flow[Person, Person, NotUsed] =
  KuduTable.flow(kuduTableSettings.withTableName("Flow"))

val f = Source(11 to 20)
  .map(i => Person(i, s"zozo_$i"))
  .via(flow)
  .runWith(Sink.fold(0)((a, d) => a + d.id))

Java

copysourceFlow<Person, Person, NotUsed> flow = KuduTable.flow(tableSettings.withTableName("Flow"));

CompletionStage<List<Person>> run =
    Source.from(Arrays.asList(200, 201, 202, 203, 204))
        .map((i) -> new Person(i, String.format("name_%d", i)))
        .via(flow)
        .toMat(Sink.seq(), Keep.right())
        .run(system);

Writing to Kudu with a Sink

Scala

copysourceval sink: Sink[Person, Future[Done]] =
  KuduTable.sink(kuduTableSettings.withTableName("Sink"))

val f = Source(1 to 10)
  .map(i => Person(i, s"zozo_$i"))
  .runWith(sink)

Java

copysourcefinal Sink<Person, CompletionStage<Done>> sink =
    KuduTable.sink(tableSettings.withTableName("Sink"));

CompletionStage<Done> o =
    Source.from(Arrays.asList(100, 101, 102, 103, 104))
        .map((i) -> new Person(i, String.format("name %d", i)))
        .runWith(sink, system);