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?

I appreciate the work that you did here @fred84 but I think that this change is way too big to solely fix #25035. It looks instead like there's a big refactoring included here too. I would prefer that the two be separated, can we focus on #25035 only first?

@jasontedor I think it is still reasonable to extract anonymous class to inner class without refactoring so I will be able to keep unit test for IndexCreationTask. Do you agree?

@fred84 A refactoring to make this unit testable is of course very much welcome but it being so large and mixing it with a bug fix is what I'm concerned with. Because the bug fix here is not tricky, I would lean towards fixing the bug first, and then refactoring. If you want to do it the other way, I'm fine with that, but let's do it in manageable bite-size chunks. 😄

@jasontedor Got it :-) I will make new pull request with bug fix only and keep this one for future discussion.

@jasontedor Fix only PR: #25380

@jasontedor As fix #25380 is merged I'll create another PR with anonymous class converted to inner and with unit test.

Thanks; since you're going to open a new pull request I will close this one.