[SPARK-11731][STREAMING] Enable batching on Driver WriteAheadLog by default

Using batching on the driver for the WriteAheadLog should be an improvement for all environments and use cases. Users will be able to scale to much higher number of receivers with the BatchedWriteAheadLog. Therefore we should turn it on by default, and QA it in the QA period.

I've also added some tests to make sure the default configurations are correct regarding recent additions:
 - batching on by default
 - closeFileAfterWrite off by default
 - parallelRecovery off by default

Author: Burak Yavuz <[email protected]>

Closes #9695 from brkyvz/enable-batch-wal.

Author: brkyvz

streaming/src/main/scala/org/apache/spark/streaming/util/WriteAheadLogUtils.scala

@@ -67,7 +67,7 @@ private[streaming] object WriteAheadLogUtils extends Logging {
   }
 
   def isBatchingEnabled(conf: SparkConf, isDriver: Boolean): Boolean = {
-    isDriver && conf.getBoolean(DRIVER_WAL_BATCHING_CONF_KEY, defaultValue = false)
+    isDriver && conf.getBoolean(DRIVER_WAL_BATCHING_CONF_KEY, defaultValue = true)
   }
 
   /**

streaming/src/test/java/org/apache/spark/streaming/JavaWriteAheadLogSuite.java

@@ -108,6 +108,7 @@ public void close() {
   public void testCustomWAL() {
     SparkConf conf = new SparkConf();
     conf.set("spark.streaming.driver.writeAheadLog.class", JavaWriteAheadLogSuite.class.getName());
+    conf.set("spark.streaming.driver.writeAheadLog.allowBatching", "false");
     WriteAheadLog wal = WriteAheadLogUtils.createLogForDriver(conf, null, null);
 
     String data1 = "data1";

streaming/src/test/scala/org/apache/spark/streaming/ReceivedBlockTrackerSuite.scala

@@ -330,8 +330,13 @@ class ReceivedBlockTrackerSuite
     : Seq[ReceivedBlockTrackerLogEvent] = {
     logFiles.flatMap {
       file => new FileBasedWriteAheadLogReader(file, hadoopConf).toSeq
-    }.map { byteBuffer =>
-      Utils.deserialize[ReceivedBlockTrackerLogEvent](byteBuffer.array)
+    }.flatMap { byteBuffer =>
+      val validBuffer = if (WriteAheadLogUtils.isBatchingEnabled(conf, isDriver = true)) {
+        Utils.deserialize[Array[Array[Byte]]](byteBuffer.array()).map(ByteBuffer.wrap)
+      } else {
+        Array(byteBuffer)
+      }
+      validBuffer.map(b => Utils.deserialize[ReceivedBlockTrackerLogEvent](b.array()))
     }.toList
   }
 

streaming/src/test/scala/org/apache/spark/streaming/util/WriteAheadLogSuite.scala

@@ -20,7 +20,7 @@ import java.io._
 import java.nio.ByteBuffer
 import java.util.{Iterator => JIterator}
 import java.util.concurrent.atomic.AtomicInteger
-import java.util.concurrent.{TimeUnit, CountDownLatch, ThreadPoolExecutor}
+import java.util.concurrent.{RejectedExecutionException, TimeUnit, CountDownLatch, ThreadPoolExecutor}
 
 import scala.collection.JavaConverters._
 import scala.collection.mutable.ArrayBuffer
@@ -190,6 +190,28 @@ abstract class CommonWriteAheadLogTests(
     }
     assert(!nonexistentTempPath.exists(), "Directory created just by attempting to read segment")
   }
+
+  test(testPrefix + "parallel recovery not enabled if closeFileAfterWrite = false") {
+    // write some data
+    val writtenData = (1 to 10).map { i =>
+      val data = generateRandomData()
+      val file = testDir + s"/log-$i-$i"
+      writeDataManually(data, file, allowBatching)
+      data
+    }.flatten
+
+    val wal = createWriteAheadLog(testDir, closeFileAfterWrite, allowBatching)
+    // create iterator but don't materialize it
+    val readData = wal.readAll().asScala.map(byteBufferToString)
+    wal.close()
+    if (closeFileAfterWrite) {
+      // the threadpool is shutdown by the wal.close call above, therefore we shouldn't be able
+      // to materialize the iterator with parallel recovery
+      intercept[RejectedExecutionException](readData.toArray)
+    } else {
+      assert(readData.toSeq === writtenData)
+    }
+  }
 }
 
 class FileBasedWriteAheadLogSuite

streaming/src/test/scala/org/apache/spark/streaming/util/WriteAheadLogUtilsSuite.scala

@@ -56,19 +56,19 @@ class WriteAheadLogUtilsSuite extends SparkFunSuite {
   test("log selection and creation") {
 
     val emptyConf = new SparkConf()  // no log configuration
-    assertDriverLogClass[FileBasedWriteAheadLog](emptyConf)
+    assertDriverLogClass[FileBasedWriteAheadLog](emptyConf, isBatched = true)
     assertReceiverLogClass[FileBasedWriteAheadLog](emptyConf)
 
     // Verify setting driver WAL class
     val driverWALConf = new SparkConf().set("spark.streaming.driver.writeAheadLog.class",
       classOf[MockWriteAheadLog0].getName())
-    assertDriverLogClass[MockWriteAheadLog0](driverWALConf)
+    assertDriverLogClass[MockWriteAheadLog0](driverWALConf, isBatched = true)
     assertReceiverLogClass[FileBasedWriteAheadLog](driverWALConf)
 
     // Verify setting receiver WAL class
     val receiverWALConf = new SparkConf().set("spark.streaming.receiver.writeAheadLog.class",
       classOf[MockWriteAheadLog0].getName())
-    assertDriverLogClass[FileBasedWriteAheadLog](receiverWALConf)
+    assertDriverLogClass[FileBasedWriteAheadLog](receiverWALConf, isBatched = true)
     assertReceiverLogClass[MockWriteAheadLog0](receiverWALConf)
 
     // Verify setting receiver WAL class with 1-arg constructor
@@ -104,6 +104,19 @@ class WriteAheadLogUtilsSuite extends SparkFunSuite {
     assertDriverLogClass[FileBasedWriteAheadLog](receiverWALConf, isBatched = true)
     assertReceiverLogClass[MockWriteAheadLog0](receiverWALConf)
   }
+
+  test("batching is enabled by default in WriteAheadLog") {
+    val conf = new SparkConf()
+    assert(WriteAheadLogUtils.isBatchingEnabled(conf, isDriver = true))
+    // batching is not valid for receiver WALs
+    assert(!WriteAheadLogUtils.isBatchingEnabled(conf, isDriver = false))
+  }
+
+  test("closeFileAfterWrite is disabled by default in WriteAheadLog") {
+    val conf = new SparkConf()
+    assert(!WriteAheadLogUtils.shouldCloseFileAfterWrite(conf, isDriver = true))
+    assert(!WriteAheadLogUtils.shouldCloseFileAfterWrite(conf, isDriver = false))
+  }
 }
 
 object WriteAheadLogUtilsSuite {