《深入理解Spark：核心思想与源代码分析》一书前言的内容请看链接《深入理解SPARK：核心思想与源代码分析》一书正式出版上市
《深入理解Spark：核心思想与源代码分析》一书第一章的内容请看链接《第1章 环境准备》
《深入理解Spark：核心思想与源代码分析》一书第二章的内容请看链接《第2章 SPARK设计理念与基本架构》
《深入理解Spark：核心思想与源代码分析》一书第三章第一部分的内容请看链接《深入理解Spark：核心思想与源代码分析》——SparkContext的初始化（伯篇）》
《深入理解Spark：核心思想与源代码分析》一书第三章第二部分的内容请看链接《深入理解Spark：核心思想与源代码分析》——SparkContext的初始化（仲篇）》
《深入理解Spark：核心思想与源代码分析》一书第三章第三部分的内容请看链接《深入理解Spark：核心思想与源代码分析》——SparkContext的初始化（叔篇）》
《深入理解Spark：核心思想与源代码分析》一书第三章第四部分的内容请看链接《深入理解Spark：核心思想与源代码分析》——SparkContext的初始化（季篇）》
Utils是Spark中最经常使用的工具类之中的一个，假设不关心事实上现，也不会对理解Spark有太多影响。可是对于Scala或者Spark的刚開始学习的人来说。通过了解Utils工具类的实现，也是个不错的入门途径。
以下将逐个介绍Utils工具类提供的经常用法。
1.localHostName
功能描写叙述：获取本地机器名。
def localHostName(): String = {
customHostname.getOrElse(localIpAddressHostname)
}
2.getDefaultPropertiesFile
功能描写叙述：获取默认的Spark属性文件。
def getDefaultPropertiesFile(env: Map[String, String] = sys.env): String = {
env.get("SPARK_CONF_DIR")
.orElse(env.get("SPARK_HOME").map{ t => s"$t${File.separator}conf"})
.map { t => new File(s"$t${File.separator}spark-defaults.conf")}
.filter(_.isFile)
.map(_.getAbsolutePath)
.orNull
}
3.loadDefaultSparkProperties
功能描写叙述：载入指定文件里的Spark属性。假设没有指定文件，则载入默认Spark属性文件的属性。
def loadDefaultSparkProperties(conf:SparkConf, filePath: String = null):String = {
val path =Option(filePath).getOrElse(getDefaultPropertiesFile())
Option(path).foreach { confFile =>
getPropertiesFromFile(confFile).filter{ case (k,v) =>
k.startsWith("spark.")
}.foreach { case (k, v) =>
conf.setIfMissing(k, v)
sys.props.getOrElseUpdate(k, v)
}
}
path
}
4.getCallSite
功能描写叙述：获取当前SparkContext的当前调用堆栈。将栈里最靠近栈底的属于spark或者Scala核心的类压入callStack的栈顶。并将此类的方法存入lastSparkMethod；将栈里最靠近栈顶的用户类放入callStack，将此类的行号存入firstUserLine。类名存入firstUserFile。终于返回的例子类CallSite存储了最短栈和长度默觉得20的最长栈的例子类。在JavaWordCount例子中。获得的数据例如以下：
- 最短栈：JavaSparkContext at JavaWordCount.java:44；
- 最长栈：org.apache.spark.api.java.JavaSparkContext.<init>(JavaSparkContext.scala:61)org.apache.spark.examples.JavaWordCount.main(JavaWordCount.java:44)。
def getCallSite(skipClass: String => Boolean =coreExclusionFunction): CallSite = {
val trace =Thread.currentThread.getStackTrace().filterNot { ste: StackTraceElement=>
ste == null || ste.getMethodName == null || ste.getMethodName.contains("getStackTrace")
}
var lastSparkMethod= "<unknown>"
var firstUserFile= "<unknown>"
var firstUserLine= 0
var insideSpark= true
var callStack= new ArrayBuffer[String]() :+ "<unknown>"
for (el<- trace) {
if (insideSpark){
if (skipClass(el.getClassName)){
lastSparkMethod = if(el.getMethodName == "<init>") {
el.getClassName.substring(el.getClassName.lastIndexOf('.') + 1)
} else {
el.getMethodName
}
callStack(0) = el.toString // Putlast Spark method on top of the stack trace.
} else {
firstUserLine = el.getLineNumber
firstUserFile = el.getFileName
callStack += el.toString
insideSpark = false
}
} else {
callStack += el.toString
}
}
val callStackDepth= System.getProperty("spark.callstack.depth","20").toInt
CallSite(
shortForm = s"$lastSparkMethod at $firstUserFile:$firstUserLine",
longForm = callStack.take(callStackDepth).mkString("\n"))
}
5.startServiceOnPort
功能描写叙述：Scala跟其他脚本语言一样。函数也能够传递，此方法正是通过回调startService这个函数来启动服务，并终于返回startService返回的service地址及port。
假设启动过程有异常。还会多次重试，直到达到maxRetries表示的最大次数。
def startServiceOnPort[T](
startPort:Int,
startService:Int => (T, Int),
conf:SparkConf,
serviceName:String = ""): (T, Int) = {
require(startPort == 0 || (1024 <= startPort && startPort < 65536),
"startPort should be between 1024 and 65535(inclusive), or 0 for a random free port.")
val serviceString= if (serviceName.isEmpty) "" elses" '$serviceName'"
val maxRetries= portMaxRetries(conf)
for (offset<- 0 to maxRetries){
val tryPort= if (startPort == 0) {
startPort
} else {
((startPort+ offset - 1024)% (65536 - 1024))+ 1024
}
try {
val (service,port) = startService(tryPort)
logInfo(s"Successfullystarted service$serviceString on port $port.")
return (service,port)
} catch {
case e:Exception if isBindCollision(e) =>
if (offset>= maxRetries) {
val exceptionMessage=
s"${e.getMessage}:Service$serviceString failed after $maxRetries retries!"
val exception= new BindException(exceptionMessage)
exception.setStackTrace(e.getStackTrace)
throw exception
}
logWarning(s"Service$serviceString couldnot bind on port $tryPort. " +
s"Attempting port ${tryPort+ 1}.")
}
}
throw newSparkException(s"Failed to start service$serviceString on port$startPort")
}
6.createDirectory
功能描写叙述：用spark+UUID的方式创建暂时文件文件夹，假设创建失败会多次重试，最多重试10次。
def createDirectory(root: String, namePrefix: String = "spark"): File = {
var attempts = 0
val maxAttempts = MAX_DIR_CREATION_ATTEMPTS
var dir: File = null
while (dir == null){
attempts += 1
if (attempts > maxAttempts) {
throw newIOException("Failed to create a temp directory(under " + root + ") after "+
maxAttempts + " attempts!")
}
try {
dir = new File(root, "spark-"+ UUID.randomUUID.toString)
if (dir.exists() || !dir.mkdirs()) {
dir = null
}
} catch { casee: SecurityException => dir = null;}
}
dir
}
7.getOrCreateLocalRootDirs
功能描写叙述：依据spark.local.dir的配置，作为本地文件的根文件夹，在创建一、二级文件夹之前要确保根文件夹是存在的。然后调用createDirectory创建一级文件夹。
private[spark] defgetOrCreateLocalRootDirs(conf: SparkConf): Array[String] = {
if (isRunningInYarnContainer(conf)) {
getYarnLocalDirs(conf).split(",")
} else {
Option(conf.getenv("SPARK_LOCAL_DIRS"))
.getOrElse(conf.get("spark.local.dir",System.getProperty("java.io.tmpdir")))
.split(",")
.flatMap {root =>
try {
val rootDir = newFile(root)
if (rootDir.exists || rootDir.mkdirs()) {
val dir = createDirectory(root)
chmod700(dir)
Some(dir.getAbsolutePath)
} else {
logError(s"Failed to create dir in $root. Ignoring this directory.")
None
}
} catch {
case e: IOException =>
logError(s"Failed to create local rootdir in $root. Ignoring this directory.")
None
}
}
.toArray
}
}
8.getLocalDir
功能描写叙述：查询Spark本地文件的一级文件夹。
def getLocalDir(conf: SparkConf): String = {
getOrCreateLocalRootDirs(conf)(0)
}
9.createTempDir
功能描写叙述：在Spark一级文件夹下创建暂时文件夹。并将文件夹注冊到shutdownDeletePaths：scala.collection.mutable.HashSet[String]中。
def createTempDir(
root: String= System.getProperty("java.io.tmpdir"),
namePrefix:String = "spark"): File = {
val dir =createDirectory(root, namePrefix)
registerShutdownDeleteDir(dir)
dir
}
10.RegisterShutdownDeleteDir
功能描写叙述：将文件夹注冊到shutdownDeletePaths：scala.collection.mutable.HashSet[String]中，以便在进程退出时删除。
def registerShutdownDeleteDir(file: File) {
val absolutePath =file.getAbsolutePath()
shutdownDeletePaths.synchronized{
shutdownDeletePaths += absolutePath
}
}
11.hasRootAsShutdownDeleteDir
功能描写叙述：推断文件是否匹配关闭时要删除的文件及文件夹，shutdownDeletePaths：scala.collection.mutable.HashSet[String]存储在进程关闭时要删除的文件及文件夹。
def hasRootAsShutdownDeleteDir(file: File): Boolean = {
val absolutePath= file.getAbsolutePath()
val retval= shutdownDeletePaths.synchronized {
shutdownDeletePaths.exists { path =>
!absolutePath.equals(path) && absolutePath.startsWith(path)
}
}
if (retval){
logInfo("path = " + file + ", already present as root for deletion.")
}
retval
}
12.deleteRecursively
功能描写叙述：用于删除文件或者删除文件夹及其子文件夹、子文件，而且从shutdownDeletePaths：scala.collection.mutable.HashSet[String]中移除此文件或文件夹。
def deleteRecursively(file: File) {
if (file != null){
try {
if (file.isDirectory &&!isSymlink(file)) {
var savedIOException:IOException = null
for (child<- listFilesSafely(file)) {
try {
deleteRecursively(child)
} catch {
case ioe:IOException => savedIOException = ioe
}
}
if (savedIOException!= null) {
throw savedIOException
}
shutdownDeletePaths.synchronized {
shutdownDeletePaths.remove(file.getAbsolutePath)
}
}
} finally {
if (!file.delete()) {
if (file.exists()) {
throw newIOException("Failed to delete: " +file.getAbsolutePath)
}
}
}
}
}
13.getSparkClassLoader
功能描写叙述：获取载入当前class的ClassLoader。
def getSparkClassLoader = getClass.getClassLoader
14.getContextOrSparkClassLoader
功能描写叙述：用于获取线程上下文的ClassLoader，没有设置时获取载入Spark的ClassLoader。
def getContextOrSparkClassLoader = Option(Thread.currentThread().getContextClassLoader).getOrElse(getSparkClassLoader)
15.newDaemonCachedThreadPool
功能描写叙述：使用Executors.newCachedThreadPool创建的缓存线程池。
def newDaemonCachedThreadPool(prefix: String): ThreadPoolExecutor = {
val threadFactory =namedThreadFactory(prefix)
Executors.newCachedThreadPool(threadFactory).asInstanceOf[ThreadPoolExecutor]
}
16.doFetchFile
功能描写叙述：使用URLConnection通过http协议下载文件。
private defdoFetchFile(url: String, targetDir: File, filename: String, conf: SparkConf,
securityMgr:SecurityManager, hadoopConf: Configuration) {
val tempFile= File.createTempFile("fetchFileTemp",null, newFile(targetDir.getAbsolutePath))
val targetFile= new File(targetDir, filename)
val uri = new URI(url)
val fileOverwrite= conf.getBoolean("spark.files.overwrite",defaultValue = false)
Option(uri.getScheme).getOrElse("file")match {
case "http"| "https" | "ftp" =>
logInfo("Fetching " + url + " to " + tempFile)
var uc:URLConnection = null
if (securityMgr.isAuthenticationEnabled()) {
logDebug("fetchFile with security enabled")
val newuri= constructURIForAuthentication(uri,securityMgr)
uc = newuri.toURL().openConnection()
uc.setAllowUserInteraction(false)
} else {
logDebug("fetchFile not using security")
uc = newURL(url).openConnection()
}
valtimeout = conf.getInt("spark.files.fetchTimeout", 60) * 1000
uc.setConnectTimeout(timeout)
uc.setReadTimeout(timeout)
uc.connect()
val in = uc.getInputStream()
downloadFile(url, in, tempFile, targetFile,fileOverwrite)
case "file"=>
val sourceFile= if (uri.isAbsolute)new File(uri)else newFile(url)
copyFile(url, sourceFile, targetFile, fileOverwrite)
case _ =>
val fs =getHadoopFileSystem(uri, hadoopConf)
val in = fs.open(newPath(uri))
downloadFile(url, in, tempFile, targetFile,fileOverwrite)
}
}
17.fetchFile
功能描写叙述：假设文件在本地有缓存。则从本地获取。否则通过HTTP远程下载。最后对.tar、.tar.gz等格式的文件解压缩后，调用shell命令行的chmod命令给文件添加a+x的权限。
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)
val fetchCacheEnabled= conf.getBoolean("spark.files.useFetchCache",defaultValue = true)
if (useCache && fetchCacheEnabled) {
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")
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()
}
copyFile(
url,
cachedFile,
targetFile,
conf.getBoolean("spark.files.overwrite",false)
)
} else {
doFetchFile(url, targetDir, fileName,conf, securityMgr, hadoopConf)
}
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)
}
FileUtil.chmod(targetFile.getAbsolutePath, "a+x")
}
18.executeAndGetOutput
功能描写叙述：运行一条command命令。而且获取它的输出。调用stdoutThread的join方法，让当前线程等待stdoutThread运行完毕。
def executeAndGetOutput(
command:Seq[String],
workingDir:File = new File("."),
extraEnvironment: Map[String, String] = Map.empty): String = {
val builder= new ProcessBuilder(command: _*)
.directory(workingDir)
val environment= builder.environment()
for ((key, value) <- extraEnvironment) {
environment.put(key,value)
}
val process= builder.start()
new Thread("readstderr for " + command(0)) {
override defrun() {
for (line<- Source.fromInputStream(process.getErrorStream).getLines()){
System.err.println(line)
}
}
}.start()
val output= new StringBuffer
val stdoutThread= new Thread("readstdout for " + command(0)) {
override defrun() {
for (line<- Source.fromInputStream(process.getInputStream).getLines()){
output.append(line)
}
}
}
stdoutThread.start()
val exitCode= process.waitFor()
stdoutThread.join() // Wait for itto finish reading output
if (exitCode!= 0) {
logError(s"Process $commandexited with code $exitCode: $output")
throw newSparkException(s"Process $command exited with code $exitCode")
}
output.toString
}
19.memoryStringToMb
功能描写叙述：将内存大小字符串转换为以MB为单位的整型值。
def memoryStringToMb(str: String): Int = {
val lower =str.toLowerCase
if (lower.endsWith("k")) {
(lower.substring(0,lower.length-1).toLong/ 1024).toInt
} else if(lower.endsWith("m")){
lower.substring(0,lower.length-1).toInt
} else if(lower.endsWith("g")){
lower.substring(0,lower.length-1).toInt* 1024
} else if(lower.endsWith("t")){
lower.substring(0,lower.length-1).toInt* 1024 * 1024
} else {// nosuffix, so it's just a number in bytes
(lower.toLong / 1024/ 1024).toInt
}
}
