Re: Cascading replication on Windows bug

On 05.09.2012 16:45, Heikki Linnakangas wrote:
> On 05.09.2012 14:28, Tom Lane wrote:
>> Heikki Linnakangas<hlinnaka(at)iki(dot)fi> writes:
>>> That doesn't work on Windows. As long as a walsender is keeping the old
>>> file open, the unlink() on it fails. You get an error like this in the
>>> startup process:
>>> FATAL: could not rename file "pg_xlog/RECOVERYXLOG" to
>>> "pg_xlog/00000001000000000000000D": Permission denied
>>
>> I thought we had some workaround for that problem. Otherwise, you'd be
>> seeing this type of failure every time a checkpoint tries to drop or
>> rename files.
>
> Hmm, now that I look at the error message more carefully, what happens
> is that the unlink() succeeds, but when the startup process tries to
> rename the new file in place, the rename() fails. The comments in
> RemoveOldXLogFiles() explains that, and also shows how to work around it:
>
>> /*
>> * On Windows, if another process (e.g another backend)
>> * holds the file open in FILE_SHARE_DELETE mode, unlink
>> * will succeed, but the file will still show up in
>> * directory listing until the last handle is closed. To
>> * avoid confusing the lingering deleted file for a live
>> * WAL file that needs to be archived, rename it before
>> * deleting it.
>> *
>> * If another process holds the file open without
>> * FILE_SHARE_DELETE flag, rename will fail. We'll try
>> * again at the next checkpoint.
>> */
>
> I think we need the same trick here, and rename the old file first, then
> unlink() it, and then rename the new file in place. I'll try that out..

Ok, committed a patch to do that.

- Heikki