[GitHub] spark pull request #14371: [SPARK-16736] Core+ SQL superfluous fs calls

[steveloughran <gi...@git.apache.org>]

Github user steveloughran commented on a diff in the pull request:

    https://github.com/apache/spark/pull/14371#discussion_r74684971
  
    --- Diff: streaming/src/main/scala/org/apache/spark/streaming/util/FileBasedWriteAheadLog.scala ---
    @@ -231,13 +232,17 @@ private[streaming] class FileBasedWriteAheadLog(
         val logDirectoryPath = new Path(logDirectory)
         val fileSystem = HdfsUtils.getFileSystemForPath(logDirectoryPath, hadoopConf)
     
    -    if (fileSystem.exists(logDirectoryPath) &&
    -        fileSystem.getFileStatus(logDirectoryPath).isDirectory) {
    -      val logFileInfo = logFilesTologInfo(fileSystem.listStatus(logDirectoryPath).map { _.getPath })
    -      pastLogs.clear()
    -      pastLogs ++= logFileInfo
    -      logInfo(s"Recovered ${logFileInfo.size} write ahead log files from $logDirectory")
    -      logDebug(s"Recovered files are:\n${logFileInfo.map(_.path).mkString("\n")}")
    +    try {
    +      if (fileSystem.getFileStatus(logDirectoryPath).isDirectory) {
    --- End diff --
    
    If you call `listStatus(file)` it returns a stat of the file, rather than listing of the children. Irritating as it's hard to differentiate listStatus(file) and listStatus(dir-with-one-child) except by examining the name of the returned status, and once you've got symlinks in the mix that differentiation isn't easy (The standard FileSystem globber has to jump though these hoops, hoops a dedicated s3a globber can/will avoid)


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