Apache Geode

Apache Geode is a distributed datagrid (formerly called “Gemfire” which used to be Pivotal’s packaging of Geode and now is VMware Tanzu).

Apache Pekko Connectors Geode provides flows and sinks to put elements into Geode, and a source to retrieve elements from it. It stores key-value-pairs. Keys and values must be serialized with Geode’s support for it.

Project Info: Apache Pekko Connectors Geode
Artifact	org.apache.pekko pekko-connectors-geode 1.0.2 Snapshots are available
JDK versions	OpenJDK 8 OpenJDK 11 OpenJDK 17
Scala versions	2.13.13, 2.12.19, 3.3.3
JPMS module name	pekko.stream.connectors.geode
License	Apache-2.0
API documentation	API (Scaladoc)
Forums	Github Discussions
Release notes	GitHub releases
Issues	Github issues
Sources	https://github.com/apache/pekko-connectors

Artifacts

sbt

val PekkoVersion = "1.0.2"
libraryDependencies ++= Seq(
  "org.apache.pekko" %% "pekko-connectors-geode" % "1.0.2",
  "org.apache.pekko" %% "pekko-stream" % PekkoVersion
)

Maven

<properties>
  <pekko.version>1.0.2</pekko.version>
  <scala.binary.version>2.13</scala.binary.version>
</properties>
<dependencies>
  <dependency>
    <groupId>org.apache.pekko</groupId>
    <artifactId>pekko-connectors-geode_${scala.binary.version}</artifactId>
    <version>1.0.2</version>
  </dependency>
  <dependency>
    <groupId>org.apache.pekko</groupId>
    <artifactId>pekko-stream_${scala.binary.version}</artifactId>
    <version>${pekko.version}</version>
  </dependency>
</dependencies>

Gradle

def versions = [
  PekkoVersion: "1.0.2",
  ScalaBinary: "2.13"
]
dependencies {
  implementation "org.apache.pekko:pekko-connectors-geode_${versions.ScalaBinary}:1.0.2"
  implementation "org.apache.pekko:pekko-stream_${versions.ScalaBinary}:${versions.PekkoVersion}"
}

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

Setup

Connection

The connection to Geode is handled by a ClientCache. A single ClientCache per application is enough. ClientCache also holds a single PDXSerializer.

The Geode client should be closed after use, it is recommended to close it on actor system termination.

Scala

copysourceval geodeSettings = GeodeSettings(hostname, port = 10334)
  .withConfiguration(c => c.setPoolIdleTimeout(10))
val geode = new Geode(geodeSettings)
system.registerOnTermination(geode.close())

Java

copysourceGeodeSettings settings =
    GeodeSettings.create(hostname, 10334).withConfiguration(c -> c.setPoolIdleTimeout(10));
Geode geode = new Geode(settings);
system.registerOnTermination(() -> geode.close());

Apache Geode supports continuous queries. Continuous query rely on server events, thus Apache Pekko Connectors Geode needs to listen to those events. This behaviour – as it consumes more resources – is isolated in a Scala trait and/or an specialized Java class.

Scala

copysourceval geode = new Geode(geodeSettings) with PoolSubscription
system.registerOnTermination(geode.close())

Java

copysourceGeodeWithPoolSubscription geode = new GeodeWithPoolSubscription(settings);

Region

Define a region setting to describe how to access region and the key extraction function.

Scala

copysourceval personsRegionSettings: RegionSettings[Int, Person] = RegionSettings("persons", (p: Person) => p.id)
val animalsRegionSettings: RegionSettings[Int, Animal] = RegionSettings("animals", (a: Animal) => a.id)
val complexesRegionSettings: RegionSettings[UUID, Complex] = RegionSettings("complexes", (a: Complex) => a.id)

Java

copysourceprotected final RegionSettings<Integer, Person> personRegionSettings =
    RegionSettings.create("persons", Person::getId);
protected final RegionSettings<Integer, Animal> animalRegionSettings =
    RegionSettings.create("animals", Animal::getId);

Serialization

Objects must be serialized to be stored in or retrieved from Geode. Only PDX format is available with Apache Pekko Connectors Geode. PDXEncoders support many options as described in Geode PDX Serialization. A PdxSerializer must be provided to Geode when reading from or writing to a region.

Scala

copysourceobject PersonPdxSerializer extends PekkoPdxSerializer[Person] {
  override def clazz: Class[Person] = classOf[Person]

  override def toData(o: scala.Any, out: PdxWriter): Boolean =
    if (o.isInstanceOf[Person]) {
      val p = o.asInstanceOf[Person]
      out.writeInt("id", p.id)
      out.writeString("name", p.name)
      out.writeDate("birthDate", p.birthDate)
      true
    } else
      false

  override def fromData(clazz: Class[_], in: PdxReader): AnyRef = {
    val id: Int = in.readInt("id")
    val name: String = in.readString("name")
    val birthDate: Date = in.readDate("birthDate")
    Person(id, name, birthDate)
  }
}

Java

copysourcepublic class PersonPdxSerializer implements PekkoPdxSerializer<Person> {

  @Override
  public Class<Person> clazz() {
    return Person.class;
  }

  @Override
  public boolean toData(Object o, PdxWriter out) {
    if (o instanceof Person) {
      Person p = (Person) o;
      out.writeInt("id", p.getId());
      out.writeString("name", p.getName());
      out.writeDate("birthDate", p.getBirthDate());
      return true;
    }
    return false;
  }

  @Override
  public Object fromData(Class<?> clazz, PdxReader in) {
    int id = in.readInt("id");
    String name = in.readString("name");
    Date birthDate = in.readDate("birthDate");
    return new Person(id, name, birthDate);
  }
}

This Apache Pekko Connectors Geode provides a generic solution for Scala users based on Shapeless for Scala 2 and for Scala 3 using the built-in tuple generic metaprogramming which may generate serializers for case classes at compile time.

Java users need to implement custom serializers manually, or use runtime reflection as described in Using Automatic Reflection-Based PDX Serialization.

Writing to Geode

This example stores data in Geode within a flow.

Scala

copysourceval flow: Flow[Person, Person, NotUsed] = geode.flow(personsRegionSettings)

val fut = source.via(flow).runWith(Sink.ignore)

Java

copysourceFlow<Person, Person, NotUsed> flow =
    geode.flow(personRegionSettings, new PersonPdxSerializer());

CompletionStage<List<Person>> run =
    source.via(flow).toMat(Sink.seq(), Keep.right()).run(system);

This example stores data in Geode by using a sink.

Scala

copysourceval animalsRegionSettings: RegionSettings[Int, Animal] =
  RegionSettings("animals", (a: Animal) => a.id)

val sink: Sink[Animal, Future[Done]] =
  geode.sink(animalsRegionSettings)

val fut: Future[Done] = source.runWith(sink)

Java

copysourceSink<Animal, CompletionStage<Done>> sink =
    geode.sink(animalRegionSettings, new AnimalPdxSerializer());

RunnableGraph<CompletionStage<Done>> runnableGraph = source.toMat(sink, Keep.right());

Reading from Geode

Simple query

Apache Geode supports simple queries.

Scala

copysourceval geode = new Geode(geodeSettings)
system.registerOnTermination(geode.close())

val source =
  geode
    .query[Person](s"select * from /persons order by id")
    .runWith(Sink.foreach(e => log.debug(s"$e")))

Java

copysourceCompletionStage<Done> personsDone =
    geode
        .query("select * from /persons", new PersonPdxSerializer())
        .runForeach(
            p -> {
              LOGGER.debug(p.toString());
            },
            system);

Continuous query

Continuous queries need to be explicitly closed, to connect creating and closing a unique identifier needs to be passed to both continuousQuery and closeContinuousQuery.

Scala

copysourceval source =
  geode
    .continuousQuery[Person](Symbol("test"), s"select * from /persons")
    .runWith(Sink.fold(0) { (c, p) =>
      log.debug(s"$p $c")
      if (c == 19) {
        geode.closeContinuousQuery(Symbol("test")).foreach { _ =>
          log.debug("test cQuery is closed")
        }

      }
      c + 1
    })

Java

copysourceCompletionStage<Done> fut =
    geode
        .continuousQuery("test", "select * from /persons", new PersonPdxSerializer())
        .runForeach(
            p -> {
              LOGGER.debug(p.toString());
              if (p.getId() == 120) {
                geode.closeContinuousQuery("test");
              }
            },
            system);

Geode basic commands

Assuming Apache Geode is installed:

gfsh

From the Geode shell:

start locator --name=locator
configure pdx --read-serialized=true
start server --name=server

create region --name=animals --type=PARTITION_REDUNDANT --redundant-copies=2
create region --name=persons --type=PARTITION_REDUNDANT --redundant-copies=2