[SPARK-21223] Change fileToAppInfo in FsHistoryProvider to fix concurrent issue.

# What issue does this PR address ?
Jira:https://issues.apache.org/jira/browse/SPARK-21223
fix the Thread-safety issue in FsHistoryProvider
Currently, Spark HistoryServer use a HashMap named fileToAppInfo in class FsHistoryProvider to store the map of eventlog path and attemptInfo.
When use ThreadPool to Replay the log files in the list and merge the list of old applications with new ones, multi thread may update fileToAppInfo at the same time, which may cause Thread-safety issues, such as  falling into an infinite loop because of calling resize func of the hashtable.

Author: 曾林西 <zenglinxi@meituan.com>

Closes #18430 from zenglinxi0615/master.

core/src/main/scala/org/apache/spark/deploy/history/FsHistoryProvider.scala

@@ -19,7 +19,7 @@ package org.apache.spark.deploy.history
 
 import java.io.{FileNotFoundException, IOException, OutputStream}
 import java.util.UUID
-import java.util.concurrent.{Executors, ExecutorService, Future, TimeUnit}
+import java.util.concurrent.{ConcurrentHashMap, Executors, ExecutorService, Future, TimeUnit}
 import java.util.zip.{ZipEntry, ZipOutputStream}
 
 import scala.collection.mutable
@@ -122,7 +122,7 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
   @volatile private var applications: mutable.LinkedHashMap[String, FsApplicationHistoryInfo]
     = new mutable.LinkedHashMap()
 
-  val fileToAppInfo = new mutable.HashMap[Path, FsApplicationAttemptInfo]()
+  val fileToAppInfo = new ConcurrentHashMap[Path, FsApplicationAttemptInfo]()
 
   // List of application logs to be deleted by event log cleaner.
   private var attemptsToClean = new mutable.ListBuffer[FsApplicationAttemptInfo]
@@ -321,7 +321,8 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
       // scan for modified applications, replay and merge them
       val logInfos: Seq[FileStatus] = statusList
         .filter { entry =>
-          val prevFileSize = fileToAppInfo.get(entry.getPath()).map{_.fileSize}.getOrElse(0L)
+          val fileInfo = fileToAppInfo.get(entry.getPath())
+          val prevFileSize = if (fileInfo != null) fileInfo.fileSize else 0L
           !entry.isDirectory() &&
             // FsHistoryProvider generates a hidden file which can't be read.  Accidentally
             // reading a garbage file is safe, but we would log an error which can be scary to
@@ -475,7 +476,7 @@ private[history] class FsHistoryProvider(conf: SparkConf, clock: Clock)
           fileStatus.getLen(),
           appListener.appSparkVersion.getOrElse("")
         )
-        fileToAppInfo(logPath) = attemptInfo
+        fileToAppInfo.put(logPath, attemptInfo)
         logDebug(s"Application log ${attemptInfo.logPath} loaded successfully: $attemptInfo")
         Some(attemptInfo)
       } else {