Github user tdas commented on a diff in the pull request:
https://github.com/apache/spark/pull/9143#discussion_r43057007
--- Diff:
streaming/src/main/scala/org/apache/spark/streaming/scheduler/ReceivedBlockTracker.scala
---
@@ -235,8 +350,67 @@ private[streaming] class ReceivedBlockTracker(
}
}
+ /**
+ * Creates a WAL Writer in a separate thread to enable batching of log
events.
+ * Exposed for tests.
+ */
+ protected def createBatchWriteAheadLogWriter(): Option[BatchLogWriter] =
{
+ if (!WriteAheadLogUtils.isBatchingEnabled(conf)) return None
+ val writer = checkpointDirOption.map(_ => new BatchLogWriter)
+ writer.foreach { runnable =>
+ new Thread(runnable, "Batch WAL Writer").start()
+ Runtime.getRuntime.addShutdownHook(new Thread {
+ override def run(): Unit = runnable.stop()
+ })
+ }
+ writer
+ }
+
/** Check if the write ahead log is enabled. This is only used for
testing purposes. */
private[streaming] def isWriteAheadLogEnabled: Boolean =
writeAheadLogOption.nonEmpty
+
+ /** A helper class that writes LogEvents in a separate thread to allow
for batching. */
+ private[streaming] class BatchLogWriter extends Runnable {
+
+ var active: Boolean = true
+
+ private def writeRecords(records: List[ReceivedBlockTrackerLogEvent]):
Unit = {
+ writeAheadLogOption.foreach { logManager =>
+ if (records.nonEmpty) {
+ logDebug(s"Batched ${records.length} records for WAL write")
+
logManager.write(ByteBuffer.wrap(Utils.serialize(CombinedRBTLogEvent(records))),
+ clock.getTimeMillis())
+ }
+ }
+ }
+
+ def stop(): Unit = {
+ active = false
+ }
+
+ private def flushRecords(): Unit = {
+ val buffer = new ArrayBuffer[ReceivedBlockTrackerLogEvent]()
+ while (!walWriteQueue.isEmpty) {
+ buffer.append(walWriteQueue.poll())
+ }
+ val records = buffer.toList
+ try {
+ writeRecords(records)
+ records.foreach(walWriteStatusMap.put(_, Success))
+ } catch {
+ case e: Exception =>
+ logWarning(s"Batch WAL Writer failed to write $records")
+ records.foreach(walWriteStatusMap.put(_, Fail))
+ }
+ }
+
+ override def run(): Unit = {
+ while (active) {
+ flushRecords()
+ Thread.sleep(WAL_WRITE_STATUS_CHECK_BACKOFF)
--- End diff --
I am a little afraid that if there is an exception in this loop, the thread
with exit and nothing will get synced. I think it may be a good idea to have
another try catch around the whole thing in run().
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