diff --git a/core/src/main/scala/org/apache/spark/internal/config/package.scala b/core/src/main/scala/org/apache/spark/internal/config/package.scala
index 512d539ee9c38a377e3884fd9ca181923d0f6d92..ef28e2c48ad02b9dd672b2afe3eb0bd369056944 100644
--- a/core/src/main/scala/org/apache/spark/internal/config/package.scala
+++ b/core/src/main/scala/org/apache/spark/internal/config/package.scala
@@ -321,6 +321,17 @@ package object config {
.intConf
.createWithDefault(3)
+ private[spark] val REDUCER_MAX_BLOCKS_IN_FLIGHT_PER_ADDRESS =
+ ConfigBuilder("spark.reducer.maxBlocksInFlightPerAddress")
+ .doc("This configuration limits the number of remote blocks being fetched per reduce task" +
+ " from a given host port. When a large number of blocks are being requested from a given" +
+ " address in a single fetch or simultaneously, this could crash the serving executor or" +
+ " Node Manager. This is especially useful to reduce the load on the Node Manager when" +
+ " external shuffle is enabled. You can mitigate the issue by setting it to a lower value.")
+ .intConf
+ .checkValue(_ > 0, "The max no. of blocks in flight cannot be non-positive.")
+ .createWithDefault(Int.MaxValue)
+
private[spark] val REDUCER_MAX_REQ_SIZE_SHUFFLE_TO_MEM =
ConfigBuilder("spark.reducer.maxReqSizeShuffleToMem")
.doc("The blocks of a shuffle request will be fetched to disk when size of the request is " +
diff --git a/core/src/main/scala/org/apache/spark/shuffle/BlockStoreShuffleReader.scala b/core/src/main/scala/org/apache/spark/shuffle/BlockStoreShuffleReader.scala
index 2fbac79a2305b9111fa13bd2d1b0c51118281780..c8d1460300934e409acf745e67e381e2ed12cec5 100644
--- a/core/src/main/scala/org/apache/spark/shuffle/BlockStoreShuffleReader.scala
+++ b/core/src/main/scala/org/apache/spark/shuffle/BlockStoreShuffleReader.scala
@@ -51,6 +51,7 @@ private[spark] class BlockStoreShuffleReader[K, C](
// Note: we use getSizeAsMb when no suffix is provided for backwards compatibility
SparkEnv.get.conf.getSizeAsMb("spark.reducer.maxSizeInFlight", "48m") * 1024 * 1024,
SparkEnv.get.conf.getInt("spark.reducer.maxReqsInFlight", Int.MaxValue),
+ SparkEnv.get.conf.get(config.REDUCER_MAX_BLOCKS_IN_FLIGHT_PER_ADDRESS),
SparkEnv.get.conf.get(config.REDUCER_MAX_REQ_SIZE_SHUFFLE_TO_MEM),
SparkEnv.get.conf.getBoolean("spark.shuffle.detectCorrupt", true))
diff --git a/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
index 81d822dc8a98f6a4a063666de6176be11fbe419c..2d176b62f8b361c1178ce77234b1f1846718b1bf 100644
--- a/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
+++ b/core/src/main/scala/org/apache/spark/storage/ShuffleBlockFetcherIterator.scala
@@ -23,7 +23,7 @@ import java.util.concurrent.LinkedBlockingQueue
import javax.annotation.concurrent.GuardedBy
import scala.collection.mutable
-import scala.collection.mutable.{ArrayBuffer, HashSet, Queue}
+import scala.collection.mutable.{ArrayBuffer, HashMap, HashSet, Queue}
import org.apache.spark.{SparkException, TaskContext}
import org.apache.spark.internal.Logging
@@ -52,6 +52,8 @@ import org.apache.spark.util.io.ChunkedByteBufferOutputStream
* @param streamWrapper A function to wrap the returned input stream.
* @param maxBytesInFlight max size (in bytes) of remote blocks to fetch at any given point.
* @param maxReqsInFlight max number of remote requests to fetch blocks at any given point.
+ * @param maxBlocksInFlightPerAddress max number of shuffle blocks being fetched at any given point
+ * for a given remote host:port.
* @param maxReqSizeShuffleToMem max size (in bytes) of a request that can be shuffled to memory.
* @param detectCorrupt whether to detect any corruption in fetched blocks.
*/
@@ -64,6 +66,7 @@ final class ShuffleBlockFetcherIterator(
streamWrapper: (BlockId, InputStream) => InputStream,
maxBytesInFlight: Long,
maxReqsInFlight: Int,
+ maxBlocksInFlightPerAddress: Int,
maxReqSizeShuffleToMem: Long,
detectCorrupt: Boolean)
extends Iterator[(BlockId, InputStream)] with TempShuffleFileManager with Logging {
@@ -110,12 +113,21 @@ final class ShuffleBlockFetcherIterator(
*/
private[this] val fetchRequests = new Queue[FetchRequest]
+ /**
+ * Queue of fetch requests which could not be issued the first time they were dequeued. These
+ * requests are tried again when the fetch constraints are satisfied.
+ */
+ private[this] val deferredFetchRequests = new HashMap[BlockManagerId, Queue[FetchRequest]]()
+
/** Current bytes in flight from our requests */
private[this] var bytesInFlight = 0L
/** Current number of requests in flight */
private[this] var reqsInFlight = 0
+ /** Current number of blocks in flight per host:port */
+ private[this] val numBlocksInFlightPerAddress = new HashMap[BlockManagerId, Int]()
+
/**
* The blocks that can't be decompressed successfully, it is used to guarantee that we retry
* at most once for those corrupted blocks.
@@ -248,7 +260,8 @@ final class ShuffleBlockFetcherIterator(
// smaller than maxBytesInFlight is to allow multiple, parallel fetches from up to 5
// nodes, rather than blocking on reading output from one node.
val targetRequestSize = math.max(maxBytesInFlight / 5, 1L)
- logDebug("maxBytesInFlight: " + maxBytesInFlight + ", targetRequestSize: " + targetRequestSize)
+ logDebug("maxBytesInFlight: " + maxBytesInFlight + ", targetRequestSize: " + targetRequestSize
+ + ", maxBlocksInFlightPerAddress: " + maxBlocksInFlightPerAddress)
// Split local and remote blocks. Remote blocks are further split into FetchRequests of size
// at most maxBytesInFlight in order to limit the amount of data in flight.
@@ -277,11 +290,13 @@ final class ShuffleBlockFetcherIterator(
} else if (size < 0) {
throw new BlockException(blockId, "Negative block size " + size)
}
- if (curRequestSize >= targetRequestSize) {
+ if (curRequestSize >= targetRequestSize ||
+ curBlocks.size >= maxBlocksInFlightPerAddress) {
// Add this FetchRequest
remoteRequests += new FetchRequest(address, curBlocks)
+ logDebug(s"Creating fetch request of $curRequestSize at $address "
+ + s"with ${curBlocks.size} blocks")
curBlocks = new ArrayBuffer[(BlockId, Long)]
- logDebug(s"Creating fetch request of $curRequestSize at $address")
curRequestSize = 0
}
}
@@ -375,6 +390,7 @@ final class ShuffleBlockFetcherIterator(
result match {
case r @ SuccessFetchResult(blockId, address, size, buf, isNetworkReqDone) =>
if (address != blockManager.blockManagerId) {
+ numBlocksInFlightPerAddress(address) = numBlocksInFlightPerAddress(address) - 1
shuffleMetrics.incRemoteBytesRead(buf.size)
if (buf.isInstanceOf[FileSegmentManagedBuffer]) {
shuffleMetrics.incRemoteBytesReadToDisk(buf.size)
@@ -443,12 +459,57 @@ final class ShuffleBlockFetcherIterator(
}
private def fetchUpToMaxBytes(): Unit = {
- // Send fetch requests up to maxBytesInFlight
- while (fetchRequests.nonEmpty &&
- (bytesInFlight == 0 ||
- (reqsInFlight + 1 <= maxReqsInFlight &&
- bytesInFlight + fetchRequests.front.size <= maxBytesInFlight))) {
- sendRequest(fetchRequests.dequeue())
+ // Send fetch requests up to maxBytesInFlight. If you cannot fetch from a remote host
+ // immediately, defer the request until the next time it can be processed.
+
+ // Process any outstanding deferred fetch requests if possible.
+ if (deferredFetchRequests.nonEmpty) {
+ for ((remoteAddress, defReqQueue) <- deferredFetchRequests) {
+ while (isRemoteBlockFetchable(defReqQueue) &&
+ !isRemoteAddressMaxedOut(remoteAddress, defReqQueue.front)) {
+ val request = defReqQueue.dequeue()
+ logDebug(s"Processing deferred fetch request for $remoteAddress with "
+ + s"${request.blocks.length} blocks")
+ send(remoteAddress, request)
+ if (defReqQueue.isEmpty) {
+ deferredFetchRequests -= remoteAddress
+ }
+ }
+ }
+ }
+
+ // Process any regular fetch requests if possible.
+ while (isRemoteBlockFetchable(fetchRequests)) {
+ val request = fetchRequests.dequeue()
+ val remoteAddress = request.address
+ if (isRemoteAddressMaxedOut(remoteAddress, request)) {
+ logDebug(s"Deferring fetch request for $remoteAddress with ${request.blocks.size} blocks")
+ val defReqQueue = deferredFetchRequests.getOrElse(remoteAddress, new Queue[FetchRequest]())
+ defReqQueue.enqueue(request)
+ deferredFetchRequests(remoteAddress) = defReqQueue
+ } else {
+ send(remoteAddress, request)
+ }
+ }
+
+ def send(remoteAddress: BlockManagerId, request: FetchRequest): Unit = {
+ sendRequest(request)
+ numBlocksInFlightPerAddress(remoteAddress) =
+ numBlocksInFlightPerAddress.getOrElse(remoteAddress, 0) + request.blocks.size
+ }
+
+ def isRemoteBlockFetchable(fetchReqQueue: Queue[FetchRequest]): Boolean = {
+ fetchReqQueue.nonEmpty &&
+ (bytesInFlight == 0 ||
+ (reqsInFlight + 1 <= maxReqsInFlight &&
+ bytesInFlight + fetchReqQueue.front.size <= maxBytesInFlight))
+ }
+
+ // Checks if sending a new fetch request will exceed the max no. of blocks being fetched from a
+ // given remote address.
+ def isRemoteAddressMaxedOut(remoteAddress: BlockManagerId, request: FetchRequest): Boolean = {
+ numBlocksInFlightPerAddress.getOrElse(remoteAddress, 0) + request.blocks.size >
+ maxBlocksInFlightPerAddress
}
}
diff --git a/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala b/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala
index 6a70cedf769b862cf9b1eeb201a28e8f434769a1..c371cbcf8dff550f0d9d0cf730f5d13290b8a69d 100644
--- a/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala
+++ b/core/src/test/scala/org/apache/spark/storage/ShuffleBlockFetcherIteratorSuite.scala
@@ -110,6 +110,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
48 * 1024 * 1024,
Int.MaxValue,
Int.MaxValue,
+ Int.MaxValue,
true)
// 3 local blocks fetched in initialization
@@ -187,6 +188,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
48 * 1024 * 1024,
Int.MaxValue,
Int.MaxValue,
+ Int.MaxValue,
true)
verify(blocks(ShuffleBlockId(0, 0, 0)), times(0)).release()
@@ -254,6 +256,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
48 * 1024 * 1024,
Int.MaxValue,
Int.MaxValue,
+ Int.MaxValue,
true)
// Continue only after the mock calls onBlockFetchFailure
@@ -319,6 +322,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
48 * 1024 * 1024,
Int.MaxValue,
Int.MaxValue,
+ Int.MaxValue,
true)
// Continue only after the mock calls onBlockFetchFailure
@@ -400,6 +404,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
48 * 1024 * 1024,
Int.MaxValue,
Int.MaxValue,
+ Int.MaxValue,
false)
// Continue only after the mock calls onBlockFetchFailure
@@ -457,6 +462,7 @@ class ShuffleBlockFetcherIteratorSuite extends SparkFunSuite with PrivateMethodT
(_, in) => in,
maxBytesInFlight = Int.MaxValue,
maxReqsInFlight = Int.MaxValue,
+ maxBlocksInFlightPerAddress = Int.MaxValue,
maxReqSizeShuffleToMem = 200,
detectCorrupt = true)
}
diff --git a/docs/configuration.md b/docs/configuration.md
index 91b5befd1b1eb3f5201e60fb638a6552dfa2501e..d3df923c42690177c89058baaab0fc8e42d114d0 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -536,6 +536,15 @@ Apart from these, the following properties are also available, and may be useful
</td>
</tr>
<tr>
+ <td><code>spark.reducer.maxBlocksInFlightPerAddress</code></td>
+ <td>Int.MaxValue</td>
+ <td>
+ This configuration limits the number of remote blocks being fetched per reduce task from a
+ given host port. When a large number of blocks are being requested from a given address in a
+ single fetch or simultaneously, this could crash the serving executor or Node Manager. This
+ is especially useful to reduce the load on the Node Manager when external shuffle is enabled.
+ You can mitigate this issue by setting it to a lower value.
+ </td>
<td><code>spark.reducer.maxReqSizeShuffleToMem</code></td>
<td>Long.MaxValue</td>
<td>