RecordIO Framing

The codec parses a ByteString stream in the RecordIO format used by Apache Mesos into distinct frames.

For instance, the response body:

128\n
{"type": "SUBSCRIBED","subscribed": {"framework_id": {"value":"12220-3440-12532-2345"},"heartbeat_interval_seconds":15.0}20\n
{"type":"HEARTBEAT"}

is parsed into frames:

{"type": "SUBSCRIBED","subscribed": {"framework_id": {"value":"12220-3440-12532-2345"},"heartbeat_interval_seconds":15.0}

{"type":"HEARTBEAT"}

Artifacts

sbt

val PekkoVersion = "1.0.2"
libraryDependencies ++= Seq(
  "org.apache.pekko" %% "pekko-connectors-simple-codecs" % "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-simple-codecs_${scala.binary.version}</artifactId>
    <version>1.0.2</version>
  </dependency>
  <dependency>
    <groupId>org.apache.pekko</groupId>
    <artifactId>pekko-stream_${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-simple-codecs_${versions.ScalaBinary}:1.0.2"
  implementation "org.apache.pekko:pekko-stream_${versions.ScalaBinary}:${versions.PekkoVersion}"
}

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

Usage

The flow factory RecordIOFramingRecordIOFraming provides a scanner factory method for a Flow[ByteString, ByteString, _]Flow<ByteString, ByteString, ?> which parses out RecordIO frames.

Scala

copysourceimport org.apache.pekko.stream.connectors.recordio.scaladsl.RecordIOFraming

val FirstRecordData =
  """{"type": "SUBSCRIBED","subscribed": {"framework_id": {"value":"12220-3440-12532-2345"},"heartbeat_interval_seconds":15.0}"""
val SecondRecordData = """{"type":"HEARTBEAT"}"""

val FirstRecordWithPrefix = s"121\n$FirstRecordData"
val SecondRecordWithPrefix = s"20\n$SecondRecordData"

val basicSource: Source[ByteString, NotUsed] =
  Source.single(ByteString(FirstRecordWithPrefix + SecondRecordWithPrefix))

  val result: Future[Seq[ByteString]] = basicSource
    .via(RecordIOFraming.scanner())
    .runWith(Sink.seq)

Java

copysourceString firstRecordData =
    "{\"type\": \"SUBSCRIBED\",\"subscribed\": {\"framework_id\": {\"value\":\"12220-3440-12532-2345\"},\"heartbeat_interval_seconds\":15.0}";
String secondRecordData = "{\"type\":\"HEARTBEAT\"}";

String firstRecordWithPrefix = "121\n" + firstRecordData;
String secondRecordWithPrefix = "20\n" + secondRecordData;

Source<ByteString, NotUsed> basicSource =
    Source.single(ByteString.fromString(firstRecordWithPrefix + secondRecordWithPrefix));

CompletionStage<List<ByteString>> result =
    basicSource.via(RecordIOFraming.scanner()).runWith(Sink.seq(), system);

We obtain:

Scala

copysourceval byteStrings = result.futureValue

byteStrings(0) shouldBe ByteString(FirstRecordData)
byteStrings(1) shouldBe ByteString(SecondRecordData)

Java

copysourceList<ByteString> byteStrings = result.toCompletableFuture().get(1, TimeUnit.SECONDS);

assertThat(byteStrings.get(0), is(ByteString.fromString(firstRecordData)));
assertThat(byteStrings.get(1), is(ByteString.fromString(secondRecordData)));

Running the example code

The code in this guide is part of runnable tests of this project. You are welcome to edit the code and run it in sbt.

Scala

sbt
> simpleCodecs/testOnly *.RecordIOFramingSpec