Github user ericl commented on a diff in the pull request:
https://github.com/apache/spark/pull/15696#discussion_r85859487
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/execution/datasources/FileCommitProtocol.scala
---
@@ -0,0 +1,223 @@
+/*
+ * 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.sql.execution.datasources
+
+import java.util.{Date, UUID}
+
+import org.apache.hadoop.fs.Path
+import org.apache.hadoop.mapreduce._
+import org.apache.hadoop.mapreduce.lib.output.FileOutputCommitter
+import org.apache.hadoop.mapreduce.task.TaskAttemptContextImpl
+
+import org.apache.spark.SparkHadoopWriter
+import org.apache.spark.internal.Logging
+import org.apache.spark.mapred.SparkHadoopMapRedUtil
+import org.apache.spark.sql.internal.SQLConf
+
+
+object FileCommitProtocol {
+ class TaskCommitMessage(obj: Any) extends Serializable
+
+ object EmptyTaskCommitMessage extends TaskCommitMessage(Unit)
+}
+
+
+/**
+ * An interface to define how a Spark job commits its outputs.
Implementations must be serializable.
+ *
+ * The proper call sequence is:
+ *
+ * 1. Driver calls setupJob.
+ * 2. As part of each task's execution, executor calls setupTask and then
commitTask
+ * (or abortTask if task failed).
+ * 3. When all necessary tasks completed successfully, the driver calls
commitJob. If the job
+ * failed to execute (e.g. too many failed tasks), the job should call
abortJob.
+ */
+abstract class FileCommitProtocol {
+ import FileCommitProtocol._
+
+ /**
+ * Setups up a job. Must be called on the driver before any other
methods can be invoked.
+ */
+ def setupJob(jobContext: JobContext): Unit
+
+ /**
+ * Commits a job after the writes succeed. Must be called on the driver.
+ */
+ def commitJob(jobContext: JobContext, taskCommits:
Seq[TaskCommitMessage]): Unit
+
+ /**
+ * Aborts a job after the writes fail. Must be called on the driver.
+ *
+ * Calling this function is a best-effort attempt, because it is
possible that the driver
+ * just crashes (or killed) before it can call abort.
+ */
+ def abortJob(jobContext: JobContext): Unit
+
+ /**
+ * Sets up a task within a job.
+ * Must be called before any other task related methods can be invoked.
+ */
+ def setupTask(taskContext: TaskAttemptContext): Unit
+
+ /**
+ * Notifies the commit protocol to add a new file, and gets back the
full path that should be
+ * used. Must be called on the executors when running tasks.
+ *
+ * A full file path consists of the following parts:
+ * 1. the base path
+ * 2. some sub-directory within the base path, used to specify
partitioning
+ * 3. file prefix, usually some unique job id with the task id
+ * 4. bucket id
+ * 5. source specific file extension, e.g. ".snappy.parquet"
+ *
+ * The "dir" parameter specifies 2, and "ext" parameter specifies both 4
and 5, and the rest
+ * are left to the commit protocol implementation to decide.
+ */
+ def addTaskTempFile(taskContext: TaskAttemptContext, dir:
Option[String], ext: String): String
+
+ /**
+ * Commits a task after the writes succeed. Must be called on the
executors when running tasks.
+ */
+ def commitTask(taskContext: TaskAttemptContext): TaskCommitMessage
+
+ /**
+ * Aborts a task after the writes have failed. Must be called on the
executors when running tasks.
+ */
+ def abortTask(taskContext: TaskAttemptContext): Unit
--- End diff --
Is this also best-effort?
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