[SPARK-1100] prevent Spark from overwriting directory silently

Thanks for Diana Carroll to report this issue (https://spark-project.atlassian.net/browse/SPARK-1100)

the current saveAsTextFile/SequenceFile will overwrite the output directory silently if the directory already exists, this behaviour is not desirable because

overwriting the data silently is not user-friendly

if the partition number of two writing operation changed, then the output directory will contain the results generated by two runnings

My fix includes:

add some new APIs with a flag for users to define whether he/she wants to overwrite the directory:
if the flag is set to true, then the output directory is deleted first and then written into the new data to prevent the output directory contains results from multiple rounds of running;

if the flag is set to false, Spark will throw an exception if the output directory already exists

changed JavaAPI part

default behaviour is overwriting

Two questions

should we deprecate the old APIs without such a flag?

I noticed that Spark Streaming also called these APIs, I thought we don't need to change the related part in streaming? @tdas

Author: CodingCat <zhunansjtu@gmail.com>

Closes #11 from CodingCat/SPARK-1100 and squashes the following commits:

6a4e3a3 [CodingCat] code clean
ef2d43f [CodingCat] add new test cases and code clean
ac63136 [CodingCat] checkOutputSpecs not applicable to FSOutputFormat
ec490e8 [CodingCat] prevent Spark from overwriting directory silently and leaving dirty directory

core/src/main/scala/org/apache/spark/rdd/PairRDDFunctions.scala

@@ -30,18 +30,15 @@ import scala.reflect.ClassTag
 
 import com.clearspring.analytics.stream.cardinality.HyperLogLog
 import org.apache.hadoop.conf.{Configurable, Configuration}
-import org.apache.hadoop.fs.Path
+import org.apache.hadoop.fs.{FileSystem, Path}
 import org.apache.hadoop.io.SequenceFile.CompressionType
 import org.apache.hadoop.io.compress.CompressionCodec
 import org.apache.hadoop.mapred.{FileOutputCommitter, FileOutputFormat, JobConf, OutputFormat}
-import org.apache.hadoop.mapreduce.{OutputFormat => NewOutputFormat}
-import org.apache.hadoop.mapreduce.{Job => NewAPIHadoopJob}
-import org.apache.hadoop.mapreduce.{RecordWriter => NewRecordWriter}
+import org.apache.hadoop.mapreduce.{OutputFormat => NewOutputFormat, Job => NewAPIHadoopJob, RecordWriter => NewRecordWriter, JobContext, SparkHadoopMapReduceUtil}
 import org.apache.hadoop.mapreduce.lib.output.{FileOutputFormat => NewFileOutputFormat}
 
 // SparkHadoopWriter and SparkHadoopMapReduceUtil are actually source files defined in Spark.
 import org.apache.hadoop.mapred.SparkHadoopWriter
-import org.apache.hadoop.mapreduce.SparkHadoopMapReduceUtil
 
 import org.apache.spark._
 import org.apache.spark.Partitioner.defaultPartitioner
@@ -604,8 +601,12 @@ class PairRDDFunctions[K: ClassTag, V: ClassTag](self: RDD[(K, V)])
     val job = new NewAPIHadoopJob(conf)
     job.setOutputKeyClass(keyClass)
     job.setOutputValueClass(valueClass)
+
     val wrappedConf = new SerializableWritable(job.getConfiguration)
-    NewFileOutputFormat.setOutputPath(job, new Path(path))
+    val outpath = new Path(path)
+    NewFileOutputFormat.setOutputPath(job, outpath)
+    val jobFormat = outputFormatClass.newInstance
+    jobFormat.checkOutputSpecs(job)
     val formatter = new SimpleDateFormat("yyyyMMddHHmm")
     val jobtrackerID = formatter.format(new Date())
     val stageId = self.id
@@ -633,7 +634,7 @@ class PairRDDFunctions[K: ClassTag, V: ClassTag](self: RDD[(K, V)])
       committer.commitTask(hadoopContext)
       return 1
     }
-    val jobFormat = outputFormatClass.newInstance
+
     /* apparently we need a TaskAttemptID to construct an OutputCommitter;
      * however we're only going to use this local OutputCommitter for
      * setupJob/commitJob, so we just use a dummy "map" task.
@@ -642,7 +643,7 @@ class PairRDDFunctions[K: ClassTag, V: ClassTag](self: RDD[(K, V)])
     val jobTaskContext = newTaskAttemptContext(wrappedConf.value, jobAttemptId)
     val jobCommitter = jobFormat.getOutputCommitter(jobTaskContext)
     jobCommitter.setupJob(jobTaskContext)
-    val count = self.context.runJob(self, writeShard _).sum
+    self.context.runJob(self, writeShard _)
     jobCommitter.commitJob(jobTaskContext)
   }
 
@@ -696,10 +697,10 @@ class PairRDDFunctions[K: ClassTag, V: ClassTag](self: RDD[(K, V)])
    * MapReduce job.
    */
   def saveAsHadoopDataset(conf: JobConf) {
-    val outputFormatClass = conf.getOutputFormat
+    val outputFormatInstance = conf.getOutputFormat
     val keyClass = conf.getOutputKeyClass
     val valueClass = conf.getOutputValueClass
-    if (outputFormatClass == null) {
+    if (outputFormatInstance == null) {
       throw new SparkException("Output format class not set")
     }
     if (keyClass == null) {
@@ -712,6 +713,12 @@ class PairRDDFunctions[K: ClassTag, V: ClassTag](self: RDD[(K, V)])
     logDebug("Saving as hadoop file of type (" + keyClass.getSimpleName + ", " +
       valueClass.getSimpleName + ")")
 
+    if (outputFormatInstance.isInstanceOf[FileOutputFormat[_, _]]) {
+      // FileOutputFormat ignores the filesystem parameter
+      val ignoredFs = FileSystem.get(conf)
+      conf.getOutputFormat.checkOutputSpecs(ignoredFs, conf)
+    }
+
     val writer = new SparkHadoopWriter(conf)
     writer.preSetup()
 

core/src/test/scala/org/apache/spark/FileSuite.scala

@@ -24,9 +24,11 @@ import scala.io.Source
 import com.google.common.io.Files
 import org.apache.hadoop.io._
 import org.apache.hadoop.io.compress.DefaultCodec
+import org.apache.hadoop.mapred.FileAlreadyExistsException
 import org.scalatest.FunSuite
 
 import org.apache.spark.SparkContext._
+import org.apache.hadoop.mapreduce.lib.output.TextOutputFormat
 
 class FileSuite extends FunSuite with LocalSparkContext {
 
@@ -208,4 +210,44 @@ class FileSuite extends FunSuite with LocalSparkContext {
     assert(rdd.count() === 3)
     assert(rdd.count() === 3)
   }
+
+  test ("prevent user from overwriting the empty directory (old Hadoop API)") {
+    sc = new SparkContext("local", "test")
+    val tempdir = Files.createTempDir()
+    val randomRDD = sc.parallelize(Array((1, "a"), (1, "a"), (2, "b"), (3, "c")), 1)
+    intercept[FileAlreadyExistsException] {
+      randomRDD.saveAsTextFile(tempdir.getPath)
+    }
+  }
+
+  test ("prevent user from overwriting the non-empty directory (old Hadoop API)") {
+    sc = new SparkContext("local", "test")
+    val tempdir = Files.createTempDir()
+    val randomRDD = sc.parallelize(Array((1, "a"), (1, "a"), (2, "b"), (3, "c")), 1)
+    randomRDD.saveAsTextFile(tempdir.getPath + "/output")
+    assert(new File(tempdir.getPath + "/output/part-00000").exists() === true)
+    intercept[FileAlreadyExistsException] {
+      randomRDD.saveAsTextFile(tempdir.getPath + "/output")
+    }
+  }
+
+  test ("prevent user from overwriting the empty directory (new Hadoop API)") {
+    sc = new SparkContext("local", "test")
+    val tempdir = Files.createTempDir()
+    val randomRDD = sc.parallelize(Array(("key1", "a"), ("key2", "a"), ("key3", "b"), ("key4", "c")), 1)
+    intercept[FileAlreadyExistsException] {
+      randomRDD.saveAsNewAPIHadoopFile[TextOutputFormat[String, String]](tempdir.getPath)
+    }
+  }
+
+  test ("prevent user from overwriting the non-empty directory (new Hadoop API)") {
+    sc = new SparkContext("local", "test")
+    val tempdir = Files.createTempDir()
+    val randomRDD = sc.parallelize(Array(("key1", "a"), ("key2", "a"), ("key3", "b"), ("key4", "c")), 1)
+    randomRDD.saveAsTextFile(tempdir.getPath + "/output")
+    assert(new File(tempdir.getPath + "/output/part-00000").exists() === true)
+    intercept[FileAlreadyExistsException] {
+      randomRDD.saveAsNewAPIHadoopFile[TextOutputFormat[String, String]](tempdir.getPath)
+    }
+  }
 }