[jira] [Created] (SPARK-23320) RANDOM pseudo environment variable has low resolution under Windows

["Olivier Sannier (JIRA)" <ji...@apache.org>]

Olivier Sannier created SPARK-23320:
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             Summary: RANDOM pseudo environment variable has low resolution under Windows
                 Key: SPARK-23320
                 URL: https://issues.apache.org/jira/browse/SPARK-23320
             Project: Spark
          Issue Type: Bug
          Components: Spark Submit
    Affects Versions: 2.1.1
         Environment: Windows 7, Windows 10

Spark 2.1.1
            Reporter: Olivier Sannier


Under Windows, spark-submit.bat calls spark-class2.cmd which then runs org.apache.spark.launcher.Main to retrieve its output and place it into the SPARK_CMD variable.

To do so, it uses a redirection to a temporary file whose name is created with this command:

{{set LAUNCHER_OUTPUT=%temp%\spark-class-launcher-output-%RANDOM%.txt}}

Note how it uses the %RANDOM% variable to get a hopefully unique name for the file that will get created.

There are two issues with this however:
 # if we have bad luck, we can get the same value RANDOM
 # bad luck is quite easy to get if we submit numerous jobs at once, because the granularity of RANDOM is based on the current second, as indicated [here|https://blogs.msdn.microsoft.com/oldnewthing/20100617-00/?p=13673].

When two concurrent spark-submit calls use the same generated file, one of them fails with a "file is in use" error message.

I would thus suggest replacing the above lines with these ones:

{{rem Because random is based on the current time, second based, it may collide quite easily.}}
{{rem To avoid this, we retry until a non existent file name is found and we create that file as soon as possible}}
{{set laucher_try_count=5}}
{{:retry_launcher}}
{{set LAUNCHER_OUTPUT=%temp%\spark-class-launcher-output-%RANDOM%.txt}}
{{if not exist "%LAUNCHER_OUTPUT%" goto :launcher_success}}
{{set /A laucher_try_count -= 1}}
{{if %laucher_try_count% GTR 0 goto :retry_launcher}}
{{echo Could not generate a launcher output filename that does not already exists 1>&2}}
{{goto :eof}}
{{:launcher_success}}
{{echo rem > %LAUNCHER_OUTPUT%}}

This code has been tried here and effectively solves the issue.

 



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