Add Sink Trait Support (#2726)

heron/api/src/scala/com/twitter/heron/streamlet/scala/Sink.scala

@@ -0,0 +1,32 @@
+//  Copyright 2018 Twitter. All rights reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+package com.twitter.heron.streamlet.scala
+
+import java.io.Serializable
+import com.twitter.heron.streamlet.Context
+
+/**
+  * Sink is how Streamlet's end. The put method invocation consumes the tuple into say
+  * external database/cache, etc. setup/cleanup is where the sink can do any one time setup work,
+  * like establishing/closing connection to sources, etc.
+  */
+trait Sink[T] extends Serializable {
+
+  def setup(context: Context): Unit
+
+  def put(tuple: T): Unit
+
+  def cleanup(): Unit
+
+}

heron/api/src/scala/com/twitter/heron/streamlet/scala/Streamlet.scala

@@ -16,7 +16,7 @@ package com.twitter.heron.streamlet.scala
 import com.twitter.heron.streamlet.{KeyValue, KeyedWindow}
 
 // TODO: This Java Streamlet API references will be changed with Scala versions when they are ready
-import com.twitter.heron.streamlet.{JoinType, SerializableTransformer, Sink, WindowConfig}
+import com.twitter.heron.streamlet.{JoinType, SerializableTransformer, WindowConfig}
 
 /**
   * A Streamlet is a (potentially unbounded) ordered collection of tuples.

heron/api/tests/scala/com/twitter/heron/streamlet/scala/SinkTest.scala

@@ -0,0 +1,65 @@
+//  Copyright 2018 Twitter. All rights reserved.
+//
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//  http://www.apache.org/licenses/LICENSE-2.0
+//
+//  Unless required by applicable law or agreed to in writing, software
+//  distributed under the License is distributed on an "AS IS" BASIS,
+//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+//  See the License for the specific language governing permissions and
+//  limitations under the License.
+package com.twitter.heron.streamlet.scala
+
+import scala.collection.mutable.ListBuffer
+
+import com.twitter.heron.streamlet.Context
+import com.twitter.heron.streamlet.scala.common.{BaseFunSuite, TestContext}
+
+/**
+  * Sink is how Streamlet's end. This class covers unit tests of Sink functionality
+  * by creating Test Sink Implementation
+  */
+class SinkTest extends BaseFunSuite {
+
+  test("Sink should support setup") {
+    val list = ListBuffer[Int]()
+    val sink = new TestSink(list)
+    sink.setup(new TestContext())
+    assert(list == List(1, 2))
+  }
+
+  test("Sink should put data") {
+    val list = ListBuffer[Int]()
+    val sink = new TestSink(list)
+    sink.setup(new TestContext())
+    sink.put(3)
+    assert(list == List(1, 2, 3))
+  }
+
+  test("Sink should support cleanup") {
+    val list = ListBuffer[Int]()
+    val sink = new TestSink(list)
+    sink.setup(new TestContext())
+    sink.put(3)
+    sink.cleanup()
+    assert(list.isEmpty)
+  }
+
+  private class TestSink(numbers: ListBuffer[Int]) extends Sink[Int] {
+
+    override def setup(context: Context): Unit = {
+      numbers += (1, 2)
+    }
+
+    override def put(tuple: Int): Unit = {
+      numbers += tuple
+    }
+
+    override def cleanup(): Unit = numbers.clear()
+
+  }
+
+}

heron/api/tests/scala/com/twitter/heron/streamlet/scala/common/TestContext.scala

@@ -44,9 +44,7 @@ private[scala] class TestContext extends Context {
                                  collectionInterval: Int,
                                  metricFn: Supplier[T]): Unit = {}
 
-  override def getState =
-    new TestState[io.Serializable, io.Serializable]()
+  override def getState = new TestState[io.Serializable, io.Serializable]()
 
 }
 
-