[Pkg-puppet-devel] Bug#698294: Bug#698294: Some simple test cases to consider

[Chris Boot]

On 06/03/13 20:40, Russ Allbery wrote:
> Chris Boot <crb at tiger-computing.co.uk> writes:
> 
>> Because people seem to think this is some obscure corner case, I thought
>> I'd write up a very simple test case to trigger the problem:
> 
> I think you've misunderstood the comments.
> 
> Everyone understands that if you use symlinks in your Puppet manifests,
> you will have this problem.  However, there is absolutely no need to use
> symlinks in your Puppet manifests, and I suspect most people don't.  You
> can point directly at the correct file with the source attribute.

I think you're right that I misunderstood the comments, and I agree in
some cases you can indeed just point the source attribute at the right
file. That won't work for us, though, but that's a different matter.

> I realize that this doesn't help you directly, since you probably have an
> existing layout scheme that uses symlinks.  And I agree that symlinks
> should work.  But a lot of people aren't going to run into this problem
> because they're not using symlinks and there really isn't any reason why
> they should need to do so.
> 
>> This time, Puppet does not produce an error at all, but the contents of
>> the file remains unchanged and un-managed. In this case, this is silent
>> corruption as Puppet fails to enforce the content change on the file.
> 
> I don't agree with this definition of "corruption."  I do agree that it's
> a bug.  But it doesn't corrupt anything.  It just fails to make a change
> that should be made.

I wouldn't have nearly as much of a problem with it if when it failed to
make the change, it made some noise about the failure. The fact is, it
does nothing and *doesn't complain* about it at all. Nobody knows the
change didn't take effect. Consider the following scenario:

User is using Puppet on a Squeeze system with file resources pointing at
symlinks, and upgrades the server and client to Wheezy. There is no
problem here yet.

User makes a change to the file pointed to by the symlink on the server.
When puppet runs on the client, nothing happens. No error, but the file
is not updated. User does not know of the error condition.

If the user notices that the file should have updated, but has not, and
tries to force the update by removing the file on the client and
re-running Puppet by hand, they will then encounter the error about
renaming temporary files.

I have actually spent the afternoon looking into this issue in much more
detail and have put an update on the pull request which was the first
attempt at fixing the upstream issue:
https://github.com/puppetlabs/puppet/pull/1476#issuecomment-14727535

To summarise my update: I still think the patch to fix the issue is
correct, but the tests to validate this are broken.

Best regards,
Chris

-- 
|Chris Boot
|Tiger Computing Ltd
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