Multi-user working copy: ownership changes

[Yves Forkl]

Hi,

yes, this post is (somehow) about the subject of multi-user working copies. I am aware that sharing a working copy is, in general, a very bad basis for collaboration, when multiple users contribute to the same working copy (risking severe conflicts and refusing to make use of proper VC at all).

However, in our scenario, we don't use this working copy for multi-lateral internal development, but solely for the exchange of data (created by us) with our customer and further partners. Hence, at least from my point of view, our entire company is to be considered as the "user" who owns this single working copy on our side.

Given that SVN strongly (and rightfully) discourages multi-user working copies, its internal locking mechanism is implemented in a way which leads to problems when different Windows users apply TortoiseSVN operations to the same working copy directory:

Certain internal SVN files (e.g. "dir-prop-base" and "entries") will change ownership to the current user and will be write-protected. As a consequence, if the Windows user who is the owner of the corking copy accesses the working copy the next time, he/she is not allowed to remove that write protection as a prerequisite to start (most) SVN operations.

In this case, the Sys Admin needs to reset ownership of the mentioned files to the original owner - which is unacceptable for production usage.

Now my question: Can you think of any solution which would satisfy the following requirements?

- A single working copy being used for data exchange with our customer.

- Multiple Windows users that are able to run TortoiseSVN on that working copy (on a Windows share) without it getting "damaged" by SVN as described above. It can be assumed that those users do not access the working copy simultaneously because there will always be only one person in charge of doing so.

One idea might be to prevent SVN from changing ownership of the mentioned files, but I fear that might be very hard to achieve.

Another idea might be to do rather the opposite, i.e. have the whole working copy change ownership to the current user as soon as someone calls any TortoiseSVN functions (so that "dir-prop-base" and "entries" will have the correct ownership). I wonder if this is feasible, though.


Of course, there also might be other approaches trying to avoid the above problem altogether. In particularly, we have come up with this one (which would require quite some changes in our setup, though):

Access the single working copy only as one single user, through a "generic" account which is mainly used to synchronize the working copy with another local directory.

It is not entirely clear to me how to do this synchronization. I suspect it would be imaginable to synchronize by means of SVN, too, which would mean setting up a second repo, but I am not sure how to establish communication between the (single) external repo's working copy on the one hand and this second (internal) repo and its working copies on the other hand...

Any thoughts?

Yves

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[Andy Levy]

On Tue, Nov 20, 2012 at 5:02 AM, Yves Forkl <yvesf...@arcor.de> wrote:

Hi,

yes, this post is (somehow) about the subject of multi-user working copies. I am aware that sharing a working copy is, in general, a very bad basis for collaboration, when multiple users contribute to the same working copy (risking severe conflicts and refusing to make use of proper VC at all).

However, in our scenario, we don't use this working copy for multi-lateral internal development, but solely for the exchange of data (created by us) with our customer and further partners. Hence, at least from my point of view, our entire company is to be considered as the "user" who owns this single working copy on our side.

I have to wonder if Subversion is the right tool for your needs in the first place. Seems like Dropbox or Skydrive might be more appropriate.

If you're staying with Subvesion, why use a WC at all? Can you map the repository as a drive via WebDAV?

 

Given that SVN strongly (and rightfully) discourages multi-user working copies, its internal locking mechanism is implemented in a way which leads to problems when different Windows users apply TortoiseSVN operations to the same working copy directory:

Certain internal SVN files (e.g. "dir-prop-base" and "entries") will change ownership to the current user and will be write-protected. As a consequence, if the Windows user who is the owner of the corking copy accesses the working copy the next time, he/she is not allowed to remove that write protection as a prerequisite to start (most) SVN operations.

In this case, the Sys Admin needs to reset ownership of the mentioned files to the original owner - which is unacceptable for production usage.

Now my question: Can you think of any solution which would satisfy the following requirements?

- A single working copy being used for data exchange with our customer.

- Multiple Windows users that are able to run TortoiseSVN on that working copy (on a Windows share) without it getting "damaged" by SVN as described above. It can be assumed that those users do not access the working copy simultaneously because there will always be only one person in charge of doing so.

One idea might be to prevent SVN from changing ownership of the mentioned files, but I fear that might be very hard to achieve.

But now you're fighting with Windows internals & security, not Subversion itself. And if it's TSVN doing these changes (which, if you're not already an admin, you must become in order to change ownership), what happens if someone uses a different Subversion client? It's really the Subversion libraries doing the WC handling here, and Windows is applying ownership & security at an even lower level than that.

You're also ignoring the fact that sharing the WC means that user A can commit user B's changes, either maliciously or unwittingly. What if a change isn't ready to be committed yet.

 

Another idea might be to do rather the opposite, i.e. have the whole working copy change ownership to the current user as soon as someone calls any TortoiseSVN functions (so that "dir-prop-base" and "entries" will have the correct ownership). I wonder if this is feasible, though.

See above.

 

Of course, there also might be other approaches trying to avoid the above problem altogether. In particularly, we have come up with this one (which would require quite some changes in our setup, though):

Access the single working copy only as one single user, through a "generic" account which is mainly used to synchronize the working copy with another local directory.

But now you'll have a loss of accountability. Changes cannot be attributed to the actual author.

[Wayne Johnson]

>
> Now my question: Can you think of any solution which would satisfy the
> following requirements?
>
> - A single working copy being used for data exchange with our customer.
>
> - Multiple Windows users that are able to run TortoiseSVN on that
> working copy (on a Windows share) without it getting "damaged" by SVN
> as described above. It can be assumed that those users do not access
> the working copy simultaneously because there will always be only one
> person in charge of doing so.

Well I don't think you can avoid the corruption if multiple users are
working on the on the same working copy at the same time. I think you need
to look at this from a different angle.

Someone has already suggested having your customer access the repository
directly through webdav.

If the only purpose is to share the information with the customer then you
could have a task that monitors the repository and exports the current
release version to the customer share automatically. It would take a
little bit of scripting work but I think it has other advantages besides
avoiding the working copy corruption.

Wayne

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[Andy Levy]

On Tue, Nov 20, 2012 at 6:42 PM, Wayne Johnson <wa...@zk.com> wrote:

>
> Now my question: Can you think of any solution which would satisfy the
> following requirements?
>
> - A single working copy being used for data exchange with our customer.
>
> - Multiple Windows users that are able to run TortoiseSVN on that
> working copy (on a Windows share) without it getting "damaged" by SVN
> as described above. It can be assumed that those users do not access
> the working copy simultaneously because there will always be only one
> person in charge of doing so.

Well I don't think you can avoid the corruption if multiple users are
working on the on the same working copy at the same time. I think you need
to look at this from a different angle.

Someone has already suggested having your customer access the repository
directly through webdav.

If the only purpose is to share the information with the customer then you
could have a task that monitors the repository and exports the current
release version to the customer share automatically. It would take a
little bit of scripting work but I think it has other advantages besides
avoiding the working copy corruption.

 

That wouldn't even require "monitoring" the repository - just write a post-commit hook script that exports what's needed to the correct location.