Fix logstash.bat not setting exit code

[dionrhys]

Release notes

Fixed Windows logstash.bat not setting exit code

What does this PR do?

This PR makes the Windows logstash.bat exit with the last %ERRORLEVEL% at the end, so that any error in running Logstash will get propagated back to the command line.

Before this change, logstash.bat would always exit with code 0 - success (when doing cmd.exe /C logstash.bat), even if the java.exe process exited with a non-zero code (e.g. due to Logstash throwing an error at runtime).

Why is it important/What is the impact to the user?

Without this change, abnormal exits from Logstash are not detected as such by an owning process (such as service wrappers NSSM or WinSW, or the Windows Task Scheduler). This means recovery actions (like restarting the process or sending a notification) will not get triggered.

I use WinSW as a service wrapper to "cmd.exe /C logstash.bat", and it was blissfully accepting of a runtime Logstash error that caused the process to exit, because the exit code being returned was 0. With this change added locally, it can now trigger its recovery actions when the error happens.

Checklist

• My code follows the style guidelines of this project
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• I have made corresponding change to the default configuration files (and/or docker env variables)
• I have added tests that prove my fix is effective or that my feature works

Author's Checklist

• Does the label bug fit with this change, or should it be enhancement?
• Consider should this have tests added?

How to test this PR locally

This is a Windows-only change.

1. Open cmd.exe to the bin folder
2. Enter cmd.exe /C logstash.bat (This invokes the script as an external process)
3. In another command prompt window, type taskkill /F /IM java.exe (or target the PID with /PID if you don't want to disrupt other java.exe processes)(/F is not optional)
4. In the original command prompt window, observe that the command has now ended
5. In the original command prompt window, enter echo %ERRORLEVEL%

Before the change in this PR, the last step would print out 0. With the change in this PR, the last step prints out 1 instead.

Logs

Before PR:

C:\Elastic\logstash\bin>cmd.exe /C logstash.bat
Using JAVA_HOME defined java: C:\Program Files\Java\jre1.8.0_171\
WARNING, using JAVA_HOME while Logstash distribution comes with a bundled JDK

~~java.exe is manually killed here~~~

C:\Elastic\logstash\bin>echo %errorlevel%
0

After PR:

C:\Elastic\logstash\bin>cmd.exe /C logstash.bat
Using JAVA_HOME defined java: C:\Program Files\Java\jre1.8.0_171\
WARNING, using JAVA_HOME while Logstash distribution comes with a bundled JDK

~~java.exe is manually killed here~~~

C:\Elastic\logstash\bin>echo %errorlevel%
1

[logstashmachine]

Since this is a community submitted pull request, a Jenkins build has not been kicked off automatically. Can an Elastic organization member please verify the contents of this patch and then kick off a build manually?

[andsel]

Hi @dionrhys ,
thank's for this PR good catch. It's good to be and will be merged after another upcoming PR which fixes a build problem on Windows

[andsel]

The fix PR is #13000

[andsel]

LGTM