Github user andrewor14 commented on a diff in the pull request: https://github.com/apache/spark/pull/1616#discussion_r17618536 --- Diff: core/src/main/scala/org/apache/spark/util/Utils.scala --- @@ -313,15 +313,83 @@ private[spark] object Utils extends Logging { } /** + * Download a file requested by the executor . Supports fetching the file in a variety of ways, + * including HTTP, HDFS and files on a standard filesystem, based on the URL parameter. + * + * If `useCache` is true, first attempts to fetch the file from a local cache that's shared across + * executors running the same application. + * + * Throws SparkException if the target file already exists and has different contents than + * the requested file. + */ + def fetchFile( + url: String, + targetDir: File, + conf: SparkConf, + securityMgr: SecurityManager, + hadoopConf: Configuration, + timestamp: Long, + useCache: Boolean) { + val fileName = url.split("/").last + val targetFile = new File(targetDir, fileName) + if (useCache) { + val cachedFileName = s"${url.hashCode}${timestamp}_cache" + val lockFileName = s"${url.hashCode}${timestamp}_lock" + val localDir = new File(getLocalDir(conf)) + val lockFile = new File(localDir, lockFileName) + val raf = new RandomAccessFile(lockFile, "rw") + // Only one executor entry. + // The FileLock is only used to control synchronization for executors download file, + // it's always safe regardless of lock type(mandatory or advisory). + val lock = raf.getChannel().lock() + val cachedFile = new File(localDir, cachedFileName) + try { + if (!cachedFile.exists()) { + doFetchFile(url, localDir, cachedFileName, conf, securityMgr, hadoopConf) + } + } finally { + lock.release() + } + if (targetFile.exists && !Files.equal(cachedFile, targetFile)) { + if (conf.getBoolean("spark.files.overwrite", false)) { + targetFile.delete() + logInfo(("File %s exists and does not match contents of %s, " + + "replacing it with %s").format(targetFile, url, url)) + } else { + throw new SparkException(s"File $targetFile exists and does not match contents of $url") + } + } + Files.copy(cachedFile, targetFile) + } else { + doFetchFile(url, targetDir, fileName, conf, securityMgr, hadoopConf) + } + + // Decompress the file if it's a .tar or .tar.gz + if (fileName.endsWith(".tar.gz") || fileName.endsWith(".tgz")) { + logInfo("Untarring " + fileName) + Utils.execute(Seq("tar", "-xzf", fileName), targetDir) + } else if (fileName.endsWith(".tar")) { + logInfo("Untarring " + fileName) + Utils.execute(Seq("tar", "-xf", fileName), targetDir) + } + // Make the file executable - That's necessary for scripts + FileUtil.chmod(targetFile.getAbsolutePath, "a+x") --- End diff -- Ah ok. I guess that's faster than copying the whole untarred directory.
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