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Re: fsync()-in webdav PUT

Maxim Dounin
February 28, 2018 09:10AM
Hello!

On Wed, Feb 28, 2018 at 10:30:08AM +0100, Nagy, Attila wrote:

> On 02/27/2018 02:24 PM, Maxim Dounin wrote:
> >
> >> Now, that nginx supports running threads, are there plans to convert at
> >> least DAV PUTs into it's own thread(pool), so make it possible to do
> >> non-blocking (from nginx's event loop PoV) fsync on the uploaded file?
> > No, there are no such plans.
> >
> > (Also, trying to do fsync() might not be the best idea even in
> > threads. A reliable server might be a better option.)
> >
> What do you mean by a reliable server?
> I want to make sure when the HTTP operation returns, the file is on the
> disk, not just in a buffer waiting for an indefinite amount of time to
> be flushed.
> This is what fsync is for.

The question here is - why you want the file to be on disk, and
not just in a buffer? Because you expect the server to die in a
few seconds without flushing the file to disk? How probable it
is, compared to the probability of the disk to die? A more
reliable server can make this probability negligible, hence the
suggestion.

(Also, another question is what "on the disk" meas from physical
point of view. In many cases this in fact means "somewhere in the
disk buffers", and a power outage can easily result in the file
being not accessible even after fsync().)

> Why doing this in a thread is not a good idea? It would'nt block nginx
> that way.

Because even in threads, fsync() is likely to cause performance
degradation. It might be a better idea to let the OS manage
buffers instead.

--
Maxim Dounin
http://mdounin.ru/
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Subject Author Posted

fsync()-in webdav PUT

Nagy, Attila February 27, 2018 05:24AM

Re: fsync()-in webdav PUT

Maxim Dounin February 27, 2018 08:26AM

Re: fsync()-in webdav PUT

Nagy, Attila February 28, 2018 04:32AM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 05:06AM

Re: fsync()-in webdav PUT

Valery Kholodkov February 28, 2018 01:26PM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 04:44PM

Re: fsync()-in webdav PUT

Aziz Rozyev February 28, 2018 05:08PM

Re: fsync()-in webdav PUT

pbooth February 28, 2018 05:36PM

Re: fsync()-in webdav PUT

Valery Kholodkov March 01, 2018 07:26AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 01, 2018 07:30AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 04:02AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 05:04AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 03:52AM

Re: fsync()-in webdav PUT

Maxim Dounin February 28, 2018 09:10AM

Re: fsync()-in webdav PUT

Valery Kholodkov February 28, 2018 01:56PM

Re: fsync()-in webdav PUT

itpp2012 February 28, 2018 03:28PM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 04:14AM

Re: fsync()-in webdav PUT

Aziz Rozyev March 02, 2018 05:44AM

Re: fsync()-in webdav PUT

Nagy, Attila March 02, 2018 06:32AM

RE: fsync()-in webdav PUT

Reinis Rozitis March 04, 2018 07:42AM

Re: fsync()-in webdav PUT

Nagy, Attila March 05, 2018 05:32AM

RE: fsync()-in webdav PUT

Reinis Rozitis March 05, 2018 06:56AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 05, 2018 08:14AM

Re: fsync()-in webdav PUT

Nagy, Attila March 05, 2018 08:56AM

Re: fsync()-in webdav PUT

Richard Demeny March 05, 2018 09:06AM

Re: fsync()-in webdav PUT

Maxim Dounin March 02, 2018 11:08AM

Re: fsync()-in webdav PUT

Valery Kholodkov March 02, 2018 02:50PM

Re: fsync()-in webdav PUT

Maxim Dounin March 02, 2018 07:44PM



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