[Kea-users] LFC Questions

[Diogo André de Assumpção]

Thanks for the quick response, Francis!

I don’t plan on running the kea-lac directly, unless as a last resort. But just wanted to confirm my understanding.

I’ll wait for the kea-lfc-start to be generally available on stable, in the meantime is there any downside to setting lfc-interval to say, 10 minutes?

Thanks,
Diogo


From: Francis Dupont <fdupont at isc.org>
Date: Wednesday, December 10, 2025 at 10:22 AM
To: Kea user's list <kea-users at lists.isc.org>
Cc: Diogo André de Assumpção <daa at meta.com>
Subject: Re: [Kea-users] LFC Questions

Diogo André de Assumpção via Kea-users writes:
> Back with some questions, this time around the LFC process.
>
> We use a memfile backend and one requirement we have is to refresh the conf=
> ig quite frequently, every 30min right now but looking to reduce that.
>
> I believe that by reloading the config either via a service restart or via =
> a =93config-reload=94 command, the LFC process will not run if our =93reloa=
> d config timer=94 < =93lfc-interval=94 set in Kea=92s config.

=> first it is a very bad idea to run lfc directly so we added a command
to have Kea to call the lfc itself (kea-lfc-start).

> Is it correct to say that the "lfc-interval=94 time, is based in the =93rel=
> oad=94  time instead of =93uptime=94, as in seen in the result of a =93stat=
> us-get=94 command?

=> the lfc-interval is run since the last time it was called, and the timer
is reset during reload (warm start). The uptime is from the cold start i.e.
when the server was launched. There is an exception to this: if the lease
file uses a previous version of CSV lfc is immediately called to convert
to the current/last version.

> My second question is related to the =93kea-lfc=94 cli. Running it directly=
>  wouldn=92t affect the running service, right? In other words, it would not=
>  replace the =93current=94 file that Kea uses to preserve the memfile=92s c=
> ontents?

=> Kea opens a lease file and write into it. You can move it and
even remove it and it will continue to write in it (of course when
it is removed you have no access to it through the file system) until
the lfc timer expire, it moves files and opens a new file. the role of
the lfc is to compress the lease history so it is preserved for Kea
warm or cold (re)start without filling the file system.

Regards

Francis Dupont <fdupont at isc.org>

PS: there are some commands to recover from disasters as removing the
lease file by accident...
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