[GitHub] [spark] zsxwing commented on a change in pull request #30492: [SPARK-33545][CORE] Support Fallback Storage during Worker decommission

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zsxwing commented on a change in pull request #30492:
URL: https://github.com/apache/spark/pull/30492#discussion_r532157411



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File path: core/src/main/scala/org/apache/spark/storage/FallbackStorage.scala
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@@ -0,0 +1,171 @@
+/*
+ * 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.storage
+
+import java.io.DataInputStream
+import java.nio.ByteBuffer
+
+import scala.concurrent.Future
+import scala.reflect.ClassTag
+
+import org.apache.hadoop.fs.{FileSystem, Path}
+
+import org.apache.spark.SparkConf
+import org.apache.spark.deploy.SparkHadoopUtil
+import org.apache.spark.internal.Logging
+import org.apache.spark.internal.config.STORAGE_DECOMMISSION_FALLBACK_STORAGE_PATH
+import org.apache.spark.network.buffer.{ManagedBuffer, NioManagedBuffer}
+import org.apache.spark.rpc.{RpcAddress, RpcEndpointRef, RpcTimeout}
+import org.apache.spark.shuffle.{IndexShuffleBlockResolver, ShuffleBlockInfo}
+import org.apache.spark.shuffle.IndexShuffleBlockResolver.NOOP_REDUCE_ID
+import org.apache.spark.util.Utils
+
+/**
+ * A fallback storage used by storage decommissioners.
+ */
+private[storage] class FallbackStorage(conf: SparkConf) extends Logging {
+  require(conf.get(STORAGE_DECOMMISSION_FALLBACK_STORAGE_PATH).isDefined)
+
+  private val fallbackPath = new Path(conf.get(STORAGE_DECOMMISSION_FALLBACK_STORAGE_PATH).get)
+  private val hadoopConf = SparkHadoopUtil.get.newConfiguration(conf)
+  private val fallbackFileSystem = FileSystem.get(fallbackPath.toUri, hadoopConf)
+
+  // Visible for testing
+  def copy(
+      shuffleBlockInfo: ShuffleBlockInfo,
+      bm: BlockManager): Unit = {
+    val shuffleId = shuffleBlockInfo.shuffleId
+    val mapId = shuffleBlockInfo.mapId
+
+    bm.migratableResolver match {
+      case r: IndexShuffleBlockResolver =>
+        val indexFile = r.getIndexFile(shuffleId, mapId)
+
+        if (indexFile.exists()) {
+          fallbackFileSystem.copyFromLocalFile(
+            new Path(indexFile.getAbsolutePath),
+            new Path(fallbackPath, s"$shuffleId/${indexFile.getName}"))
+
+          val dataFile = r.getDataFile(shuffleId, mapId)
+          if (dataFile.exists()) {
+            fallbackFileSystem.copyFromLocalFile(
+              new Path(dataFile.getAbsolutePath),
+              new Path(fallbackPath, s"$shuffleId/${dataFile.getName}"))

Review comment:
       Should we add the application id to the path? For example, a user may just run the same codes multiple times. It would be more convenient if the user doesn't need to use a different configuration value for each run.




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