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Re: fsync()-in webdav PUT

Valery Kholodkov
February 28, 2018 01:26PM
It's completely clear why someone would need to flush file's data and
metadata upon a WebDAV PUT operation. That is because many architectures
expect a PUT operation to be completely settled before a reply is returned.

Without fsyncing file's data and metadata a client will receive a
positive reply before data has reached the storage, thus leaving
non-zero probability that states of two systems involved into a web
transaction end up inconsistent.

Further, the exact moment when the data of certain specific file reaches
the storage depends on numerous factors, for example, I/O contention.
Consequently, the exact moment when the data of a file being uploaded
reaches the storage can be only determined by executing fsync.

val

On 28-02-18 11:04, Aziz Rozyev wrote:
> While it’s not clear why one may need to flush the data on each http operation,
> I can imagine to what performance degradation that may lead of.
>
> if it’s not a some kind of funny clustering among nodes, I wouldn't care much
> where actual data is, RAM still should be much faster, than disk I/O.
>
>
> br,
> Aziz.
>
>
>
>
>
>> On 28 Feb 2018, at 12:30, Nagy, Attila <bra@fsn.hu> 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.
>>
>> Why doing this in a thread is not a good idea? It would'nt block nginx that way.

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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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