[SPARK-3054][STREAMING] Add unit tests for Spark Sink.

This patch adds unit tests for Spark Sink.

It also removes the private[flume] for Spark Sink,
since the sink is instantiated from Flume configuration (looks like this is ignored by reflection which is used by
Flume, but we should still remove it anyway).

Author: Hari Shreedharan <hshreedharan@apache.org>
Author: Hari Shreedharan <hshreedharan@cloudera.com>

Closes #1958 from harishreedharan/spark-sink-test and squashes the following commits:

e3110b9 [Hari Shreedharan] Add a sleep to allow sink to commit the transactions
120b81e [Hari Shreedharan] Fix complexity in threading model in test
4df5be6 [Hari Shreedharan] Merge remote-tracking branch 'asf/master' into spark-sink-test
c9190d1 [Hari Shreedharan] Indentation and spaces changes
7fedc5a [Hari Shreedharan] Merge remote-tracking branch 'asf/master' into spark-sink-test
abc20cb [Hari Shreedharan] Minor test changes
7b9b649 [Hari Shreedharan] Merge branch 'master' into spark-sink-test
f2c56c9 [Hari Shreedharan] Update SparkSinkSuite.scala
a24aac8 [Hari Shreedharan] Remove unused var
c86d615 [Hari Shreedharan] [SPARK-3054][STREAMING] Add unit tests for Spark Sink.

external/flume-sink/pom.xml

@@ -72,6 +72,13 @@
       <groupId>org.scalatest</groupId>
       <artifactId>scalatest_${scala.binary.version}</artifactId>
     </dependency>
+    <dependency>
+      <groupId>org.apache.spark</groupId>
+      <artifactId>spark-streaming_${scala.binary.version}</artifactId>
+      <version>${project.version}</version>
+      <type>test-jar</type>
+      <scope>test</scope> <!-- Need it only for tests, don't package it -->
+    </dependency>
   </dependencies>
   <build>
     <outputDirectory>target/scala-${scala.binary.version}/classes</outputDirectory>

external/flume-sink/src/main/scala/org/apache/spark/streaming/flume/sink/SparkSink.scala

@@ -53,7 +53,6 @@ import org.apache.flume.sink.AbstractSink
  *
  */
 
-private[flume]
 class SparkSink extends AbstractSink with Logging with Configurable {
 
   // Size of the pool to use for holding transaction processors.

external/flume-sink/src/test/scala/org/apache/spark/streaming/flume/sink/SparkSinkSuite.scala

@@ -0,0 +1,204 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You 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 org.apache.spark.streaming.flume.sink
+
+import java.net.InetSocketAddress
+import java.util.concurrent.atomic.AtomicInteger
+import java.util.concurrent.{TimeUnit, CountDownLatch, Executors}
+
+import scala.collection.JavaConversions._
+import scala.concurrent.{ExecutionContext, Future}
+import scala.util.{Failure, Success}
+
+import com.google.common.util.concurrent.ThreadFactoryBuilder
+import org.apache.avro.ipc.NettyTransceiver
+import org.apache.avro.ipc.specific.SpecificRequestor
+import org.apache.flume.Context
+import org.apache.flume.channel.MemoryChannel
+import org.apache.flume.event.EventBuilder
+import org.apache.spark.streaming.TestSuiteBase
+import org.jboss.netty.channel.socket.nio.NioClientSocketChannelFactory
+
+class SparkSinkSuite extends TestSuiteBase {
+  val eventsPerBatch = 1000
+  val channelCapacity = 5000
+
+  test("Success") {
+    val (channel, sink) = initializeChannelAndSink()
+    channel.start()
+    sink.start()
+
+    putEvents(channel, eventsPerBatch)
+
+    val port = sink.getPort
+    val address = new InetSocketAddress("0.0.0.0", port)
+
+    val (transceiver, client) = getTransceiverAndClient(address, 1)(0)
+    val events = client.getEventBatch(1000)
+    client.ack(events.getSequenceNumber)
+    assert(events.getEvents.size() === 1000)
+    assertChannelIsEmpty(channel)
+    sink.stop()
+    channel.stop()
+    transceiver.close()
+  }
+
+  test("Nack") {
+    val (channel, sink) = initializeChannelAndSink()
+    channel.start()
+    sink.start()
+    putEvents(channel, eventsPerBatch)
+
+    val port = sink.getPort
+    val address = new InetSocketAddress("0.0.0.0", port)
+
+    val (transceiver, client) = getTransceiverAndClient(address, 1)(0)
+    val events = client.getEventBatch(1000)
+    assert(events.getEvents.size() === 1000)
+    client.nack(events.getSequenceNumber)
+    assert(availableChannelSlots(channel) === 4000)
+    sink.stop()
+    channel.stop()
+    transceiver.close()
+  }
+
+  test("Timeout") {
+    val (channel, sink) = initializeChannelAndSink(Map(SparkSinkConfig
+      .CONF_TRANSACTION_TIMEOUT -> 1.toString))
+    channel.start()
+    sink.start()
+    putEvents(channel, eventsPerBatch)
+    val port = sink.getPort
+    val address = new InetSocketAddress("0.0.0.0", port)
+
+    val (transceiver, client) = getTransceiverAndClient(address, 1)(0)
+    val events = client.getEventBatch(1000)
+    assert(events.getEvents.size() === 1000)
+    Thread.sleep(1000)
+    assert(availableChannelSlots(channel) === 4000)
+    sink.stop()
+    channel.stop()
+    transceiver.close()
+  }
+
+  test("Multiple consumers") {
+    testMultipleConsumers(failSome = false)
+  }
+
+  test("Multiple consumers with some failures") {
+    testMultipleConsumers(failSome = true)
+  }
+
+  def testMultipleConsumers(failSome: Boolean): Unit = {
+    implicit val executorContext = ExecutionContext
+      .fromExecutorService(Executors.newFixedThreadPool(5))
+    val (channel, sink) = initializeChannelAndSink()
+    channel.start()
+    sink.start()
+    (1 to 5).foreach(_ => putEvents(channel, eventsPerBatch))
+    val port = sink.getPort
+    val address = new InetSocketAddress("0.0.0.0", port)
+    val transceiversAndClients = getTransceiverAndClient(address, 5)
+    val batchCounter = new CountDownLatch(5)
+    val counter = new AtomicInteger(0)
+    transceiversAndClients.foreach(x => {
+      Future {
+        val client = x._2
+        val events = client.getEventBatch(1000)
+        if (!failSome || counter.getAndIncrement() % 2 == 0) {
+          client.ack(events.getSequenceNumber)
+        } else {
+          client.nack(events.getSequenceNumber)
+          throw new RuntimeException("Sending NACK for failure!")
+        }
+        events
+      }.onComplete {
+        case Success(events) =>
+          assert(events.getEvents.size() === 1000)
+          batchCounter.countDown()
+        case Failure(t) =>
+          // Don't re-throw the exception, causes a nasty unnecessary stack trace on stdout
+          batchCounter.countDown()
+      }
+    })
+    batchCounter.await()
+    TimeUnit.SECONDS.sleep(1) // Allow the sink to commit the transactions.
+    executorContext.shutdown()
+    if(failSome) {
+      assert(availableChannelSlots(channel) === 3000)
+    } else {
+      assertChannelIsEmpty(channel)
+    }
+    sink.stop()
+    channel.stop()
+    transceiversAndClients.foreach(x => x._1.close())
+  }
+
+  private def initializeChannelAndSink(overrides: Map[String, String] = Map.empty): (MemoryChannel,
+    SparkSink) = {
+    val channel = new MemoryChannel()
+    val channelContext = new Context()
+
+    channelContext.put("capacity", channelCapacity.toString)
+    channelContext.put("transactionCapacity", 1000.toString)
+    channelContext.put("keep-alive", 0.toString)
+    channelContext.putAll(overrides)
+    channel.configure(channelContext)
+
+    val sink = new SparkSink()
+    val sinkContext = new Context()
+    sinkContext.put(SparkSinkConfig.CONF_HOSTNAME, "0.0.0.0")
+    sinkContext.put(SparkSinkConfig.CONF_PORT, 0.toString)
+    sink.configure(sinkContext)
+    sink.setChannel(channel)
+    (channel, sink)
+  }
+
+  private def putEvents(ch: MemoryChannel, count: Int): Unit = {
+    val tx = ch.getTransaction
+    tx.begin()
+    (1 to count).foreach(x => ch.put(EventBuilder.withBody(x.toString.getBytes)))
+    tx.commit()
+    tx.close()
+  }
+
+  private def getTransceiverAndClient(address: InetSocketAddress,
+    count: Int): Seq[(NettyTransceiver, SparkFlumeProtocol.Callback)] = {
+
+    (1 to count).map(_ => {
+      lazy val channelFactoryExecutor =
+        Executors.newCachedThreadPool(new ThreadFactoryBuilder().setDaemon(true).
+          setNameFormat("Flume Receiver Channel Thread - %d").build())
+      lazy val channelFactory =
+        new NioClientSocketChannelFactory(channelFactoryExecutor, channelFactoryExecutor)
+      val transceiver = new NettyTransceiver(address, channelFactory)
+      val client = SpecificRequestor.getClient(classOf[SparkFlumeProtocol.Callback], transceiver)
+      (transceiver, client)
+    })
+  }
+
+  private def assertChannelIsEmpty(channel: MemoryChannel): Unit = {
+    assert(availableChannelSlots(channel) === channelCapacity)
+  }
+
+  private def availableChannelSlots(channel: MemoryChannel): Int = {
+    val queueRemaining = channel.getClass.getDeclaredField("queueRemaining")
+    queueRemaining.setAccessible(true)
+    val m = queueRemaining.get(channel).getClass.getDeclaredMethod("availablePermits")
+    m.invoke(queueRemaining.get(channel)).asInstanceOf[Int]
+  }
+}

external/flume/src/test/scala/org/apache/spark/streaming/flume/FlumePollingStreamSuite.scala

@@ -198,7 +198,7 @@ class FlumePollingStreamSuite extends TestSuiteBase {
   }
 
   def assertChannelIsEmpty(channel: MemoryChannel) = {
-    val queueRemaining = channel.getClass.getDeclaredField("queueRemaining");
+    val queueRemaining = channel.getClass.getDeclaredField("queueRemaining")
     queueRemaining.setAccessible(true)
     val m = queueRemaining.get(channel).getClass.getDeclaredMethod("availablePermits")
     assert(m.invoke(queueRemaining.get(channel)).asInstanceOf[Int] === 5000)