Re: fsmonitor on linux is triggered due to unison changes its fingerprint cache

Hi,

Am 26.09.25 um 04:35 schrieb 'Dale R. Worley' via unison-users:
> [send send attempt]
> 
> Ulrich Gemkow <[email protected]> writes:
>> On Sunday 21 September 2025, Dale R. Worley wrote:
>>> My understanding of all this is weak, but I notice an oddity in this bug
>>> report that nobody else seems to have commented on:
>>>
>>> Ulrich Gemkow <[email protected]> writes:
>>>> The inotify watch tool shows this sequence about every second:
>>>>
>>>> # ~/.unison/homesync/ OPEN fpd51d53afbd71ea49fcec7a981a36e25f
>>>> # ~/.unison/homesync/ ACCESS fpd51d53afbd71ea49fcec7a981a36e25f
>>>> # ~/.unison/homesync/ CLOSE_NOWRITE,CLOSE fpd51d53afbd71ea49fcec7a981a36e25f
>>>> # ~/.unison/homesync/ OPEN fpd51d53afbd71ea49fcec7a981a36e25f
>>>> # ~/.unison/homesync/ MODIFY fpd51d53afbd71ea49fcec7a981a36e25f
>>>> # ~/.unison/homesync/ CLOSE_WRITE,CLOSE fpd51d53afbd71ea49fcec7a981a36e25f
>>>
>>> That line that says "MODIFY" -- what is being modified and who is
>>> modifying it?  Your report says that nothing has been changed in the
>>> actual user files and that Unison makes no changes.
>>
>> This is the output of a tool which uses the Linux inotify syscall to
>> watch for changes in a directory tree. It tells that the file named
>> at the end of the line is modified ((fpd51d53afbd71ea49fcec7a981a36e25f).
>>
>> This is unisons fingerprint file.
> 
> Ah!  I had assumed that "fpd51d53afbd71ea49fcec7a981a36e25f" was some
> sort of internal code.
> 
> The let me propose this sequence of events:
> 
> 1. Unison wakes up and runs.
> 2. No files have changed, so it doesn't do anything.
> 3. Unison does not change the contents of fpNNNNNNNN but it updates its
> modification date.
> 4. Unison sleeps.
> 5. fsmonitor is notified that the modification date of fpNNNNNNNN has
> changed.
> 6. fsmonitor wakes up Unison.
> 7. Unison wakes up and runs.
> etc.
> 
> What we need for this situation is that if Unison detects no changes, it
> should not modify the file system, not even the files in ~/.unison.  In
> particular, it should not change the fp* file if it does not change its
> contents.
> 
> Dale

what about excluding these files from being watched by inotifywait using
paramter @<file>?


-- 
Mit freundlichem Gruß                                 Best regards
                                 Kirkorowicz

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