Rename doesn't work inside unix volumes

[bbuie]

but copy and unlink is identical and has no issue.

[malarzm]

@bbuie thanks for the PR! What are the symptoms of not working rename though?

[bbuie]

@malarzm Put the file your trying to rename in a volume. I'm using docker, so a
cache folder is in a folder on my local machine mounted to a folder in
Ubuntu 14.04. I get an error, "permission denied"

Here is more info: http://php.net/manual/en/function.rename.php#117590

On Monday, September 19, 2016, Maciej Malarz notifications@github.com
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@bbuie https://github.com/bbuie thanks for the PR! What are the
symptoms of not working rename though?

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[alcaeus]

This shouldn't be an issue. As you can see in the code, $tmpFileName is $fileName with a hash attached so the operation remains atomic. Assuming you're writing the cache files in /code/app/var/cache/doctrine/hydrators the rename would just be the following:

rename('/code/app/var/cache/doctrine/hydrators/SampleHydrator.php.abcdef', '/code/app/var/cache/doctrine/hydrators/SampleHydrator.php')

This rename shouldn't go across devices since the files stay in the same folder. Thus, I'm closing the issue - if you can reproduce this for us in a vagrant box feel free to open an issue providing tips how to reproduce it.

[bbuie]

@alcaeus but it is an issue. In fact, it is a known issue to the php community:

http://php.net/manual/en/function.rename.php#117590

It happens when mongodb-odm is installed outside a volume and your trying to rename a file inside a volume.

Not only is the issue documented by the PHP community, it was an issue for me using mongodb-odm as part of a system built using docker.

It was a pain to find the fix and once found I patched it and submitted the changes to you (only two lines of changed code that is identical to the functionality of the old code) to make this code more accessible to other systems using volumes.

This patch fixed the issue on my machine and it will help others.

[alcaeus]

I have not yet managed to reproduce the problem, our docker machines don't show this problem at all, which is why I asked you to provide a way to reproduce the problem.

The reason why I'm hesitant to simply replace rename() with copy() followed by unlink() is atomicity: rename() is atomic while copy() isn't and can cause problems on slow file systems or with large files. You could end up with a script loading a partially written proxy file, causing a fatal error during script execution. That's why we write a temporary file and then rename it in the first place. If we were to do copy/unlink we might as well write the file directly.

[bbuie]

@alcaeus that makes sense.

The only steps to recreate I can provide is setup a docker container where mongodb-odm is installed in the container but the file you're trying to rename is in a volume.

But I think I already said that, so I may need to table this.

[alcaeus]

I've tried reproducing this after running into a problem similar to this one and symfony/symfony#12533. So, I've come up with a gist that reproduces the general problem of cross-device renames: https://gist.github.com/alcaeus/a367e895e6c55f7fb93870dcba46efa9

The problem I was able to reproduce was renaming a folder across device, but I couldn't reproduce it with a file. Are you sure the problem you're hitting is due to ODM and not the Symfony cache?

[bbuie]

@alcaeus I can't say for sure if it is with Symfony cache or ODM, I just know that by changing rename to copy and unlink it fixes my issue.