make sure to generate unique output file

Author: Ngone51

bin/spark-class2.cmd

@@ -63,7 +63,12 @@ if not "x%JAVA_HOME%"=="x" (
 
 rem The launcher library prints the command to be executed in a single line suitable for being
 rem executed by the batch interpreter. So read all the output of the launcher into a variable.
+:gen
 set LAUNCHER_OUTPUT=%temp%\spark-class-launcher-output-%RANDOM%.txt
+rem SPARK-28302: %RANDOM% would return the same number if we call it instantly after last call,
+rem so we should make sure to generate unique file to avoid process collision of writing into a
+rem same file concurrently.
+if exist %LAUNCHER_OUTPUT% goto :gen
 "%RUNNER%" -Xmx128m -cp "%LAUNCH_CLASSPATH%" org.apache.spark.launcher.Main %* > %LAUNCHER_OUTPUT%
 for /f "tokens=*" %%i in (%LAUNCHER_OUTPUT%) do (
   set SPARK_CMD=%%i