DHCP restart with bulk lease data

[Sten Carlsen]

On 30-10-2019 11.59, Surya Teja wrote:
> I was thinking that since it leaves the .<time> file present, it may
> have problems doing the file operations. 
> I did some experimenting, whatever way I make the files write
> protected, dhcpd manages to change them back. The only thing I did not
> test is SELinux.
> -------> Sten, can you suggest few steps to cross check on how to
> confirm that would be file operations issues when it has bulk data
What I did was to deliberately write-protect the files in various
combinations including giving the /var/lib/dhcp a new owner and write
protect it, then restart dhcpd. In my setup the file operations always
finished with no visible delay or other hickups. I was a bit surprised
as I did not expect dhcpd to be able to touch a write-protected file
that it does not own.
>
> On Tue, Oct 29, 2019 at 7:11 PM Sten Carlsen <stenc at s-carlsen.dk
> <mailto:stenc at s-carlsen.dk>> wrote:
>
>
>
>
>>     On 29 Oct 2019, at 13.49, Surya Teja <suryateja042 at gmail.com
>>     <mailto:suryateja042 at gmail.com>> wrote:
>>
>>     Could there be issues with file permissions?
>>     My guess is that the temporary file written can not be renamed
>>     because dhcpd does not have write permissions?   ------>
>>     Hi Sten, I don't think it is with permission because after few
>>     minutes dhcpd is restarting and granting lease, the issue is it
>>     is taking long time,
>
>     I was thinking that since it leaves the .<time> file present, it
>     may have problems doing the file operations. 
>     I did some experimenting, whatever way I make the files write
>     protected, dhcpd manages to change them back. The only thing I did
>     not test is SELinux.
>
>>     In the isc dhcp forum I observed few options like  dont-use-fsync
>>     but it also suggest not recommended until thorough understanding OS 
>>     I have installed the dhcpd on centos7, does any one have used
>>     this option? Any experience with it would be much helpful for me     
>>
>>     Thanks in advance
>>
>>     On Tue, Oct 29, 2019 at 6:12 PM Surya Teja
>>     <suryateja042 at gmail.com <mailto:suryateja042 at gmail.com>> wrote:
>>
>>         you're doing something wrong. With a decent disk subsystem
>>         this is expected to take a few *seconds* (5 - 10 seconds
>>         would be my estimate ) ---->
>>         Hi  sthaug I don't see any disk subsystem issues, may be I am
>>         missing the cases, can you please suggest the areas or
>>         commands to cross check if possible?
>>
>>
>>         Thanks Teja
>>
>>         On Tue, Oct 29, 2019 at 5:13 PM Sten Carlsen
>>         <stenc at s-carlsen.dk <mailto:stenc at s-carlsen.dk>> wrote:
>>
>>
>>
>>             > On 29 Oct 2019, at 11.20, sthaug at nethelp.no
>>             <mailto:sthaug at nethelp.no> wrote:
>>             >
>>             >> The main thing I am facing the issue is when the data
>>             is too high like
>>             >> 50-60k leases in the file, the dhcpd service restart
>>             is taking more time
>>             >> (nearly 5-6 minutes) some times nearly 10-11 mins
>>             >
>>             > If a dhcpd restart with 50 - 60k leases takes 5-6
>>             minutes or more,
>>             > you're doing something wrong. With a decent disk
>>             subsystem this is
>>             > expected to take a few *seconds* (5 - 10 seconds would
>>             be my estimate
>>             > based on what we see here with a larger leases file).
>>
>>             Could there be issues with file permissions?
>>
>>             My guess is that the temporary file written can not be
>>             renamed because dhcpd does not have write permissions?
>>
>>             >
>>             > Steinar Haug, Nethelp consulting, sthaug at nethelp.no
>>             <mailto:sthaug at nethelp.no>
>>             > _______________________________________________
>>             > dhcp-users mailing list
>>             > dhcp-users at lists.isc.org <mailto:dhcp-users at lists.isc.org>
>>             > https://lists.isc.org/mailman/listinfo/dhcp-users
>>
>
-- 
Best regards

Sten Carlsen

No improvements come from shouting:

"MALE BOVINE MANURE!!!" 

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