Sonarqube->SVN Authentication required error although supplied - jenkins

Question

I'm setting up sonarqube scan jobs in Jenkins and I have ensured to provide my svn credentials in sonarqube at 'Administration>Configuration>SCM>Username+Password.
Most of the jobs scan fine with svn blame data however one particular job I'm still getting the authentication error as below during the scm data scanning phase:
19:42:06.883 INFO: SCM provider for this project is: svn
19:42:06.883 INFO: 10938 files to be analyzed
19:42:16.899 INFO: 3/10938 files analyzed
19:42:26.901 INFO: 4/10938 files analyzed
.......
19:46:27.024 INFO: 246/10938 files analyzed
19:46:37.028 INFO: 247/10938 files analyzed
19:46:47.036 INFO: 247/10938 files analyzed
19:46:57.044 INFO: 247/10938 files analyzed
19:47:07.044 INFO: 247/10938 files analyzed
19:47:17.044 INFO: 247/10938 files analyzed
19:47:27.044 INFO: 247/10938 files analyzed
19:47:37.044 INFO: 247/10938 files analyzed
19:47:40.763 INFO: 248/10938 files analyzed
19:47:40.888 INFO: ------------------------------------------------------------------------
19:47:40.888 INFO: EXECUTION FAILURE
19:47:40.888 INFO: ------------------------------------------------------------------------
19:47:40.888 INFO: Total time: 2:02:46.450s
19:47:41.075 INFO: Final Memory: 36M/3064M
19:47:41.075 INFO: ------------------------------------------------------------------------
19:47:41.075 ERROR: Error during SonarQube Scanner execution
19:47:41.075 ERROR: Error when executing blame for file foo/bar.java
19:47:41.075 ERROR: Caused by: svn: E170001: Authentication required for '<http://svn-app:1234> john'
19:47:41.075 ERROR:
19:47:41.075 ERROR: Re-run SonarQube Scanner using the -X switch to enable full debug logging.
WARN: Unable to locate 'report-task.txt' in the workspace. Did the SonarScanner succedeed?
ERROR: SonarQube scanner exited with non-zero code: 1
Finished: FAILURE
What's weird is that I've ran this scan multiple times and this error always pop around the 240-250th file it was analyzing i.e. not always the same file. Weirdly, authentication went through initially, just that around the 240-250th file then this error pops.
Various solutions recommend to disable scm sensor (sonar.scm.disabled=true) which my requirements forbids. I need the scm blame data.
I have tried the following things:
Restarting Jenkins Server
Restarting Sonarqube Server
Restarting SVN Server
In jenkins job configuration> sonarqube analysis properties, setting sonar.scm.username and sonar.scm.password
Deleting the job as well as workspace and recreating a new job.

Answer 1

Turns out it was due to the KeepAliveTimeout parameter at SVN being set too low. When it was analyzing the particular large file then it hits this timeout (for instance, more than 1 minute on the 207th file as per my code example), causing SVN to rechallenge sonarqube for credentials.
Now other svn clients would've created a credential cache under %HOMEPATH%/AppData/Roaming/Subversion/auth/svn.simple/ and retrieve this cache when this situation is encountered. However Sonarqube's svn plugin (svnkit) does not store credentials cache, and even if a cache exist it would not know how to read it(tried it with both encrypted and plaintext cache).
Editing the svn's KeepAliveTimeout parameter in httpd.conf solved this problem with a trade-off on svn server's performance theoretically - because svn would have wait longer before confirming a client is idle to close connection to reclaim resources, so increasing the KeepAliveTimeout parameter would cause svn to hold more requests at any given time.
References:
SVN Authentication Network Model: http://svnbook.red-bean.com/nightly/en/svn.serverconfig.netmodel.html#svn.serverconfig.netmodel.creds
Similar Issue: https://groups.google.com/forum/#!topic/sonarqube/-Vz2zoOBS1Y
SVNkit Authentication Mechanism: https://wiki.svnkit.com/Authentication:
https://github.com/jenkinsci/svnkit
Sonarqube SVNkit plugin repo: https://github.com/SonarSource/sonar-scm-svn
Jenkins SVNkit plugin repo: https://github.com/jenkinsci/svnkit