[Kea-users] How to best update the KEA configuration on a HA hot-standby KEA setup

Fri Nov 18 16:03:23 UTC 2022

I am running Kea on RockyLinux8 and RHEL8.  For those systems I usually run
"service kea-dhcp4 reload" and "service kea-dhcp6 reload" anytime I update
the .json configuration files.  And as far as I can tell, when I do that
there are no DHCP replies from the server for 10-20 seconds.  Or at least
nothing is logged during that time.  I have not looked at that very closely
as reloading the Kea service is not very common for us now that it is all
up and running.

--Dan

On Fri, Nov 18, 2022 at 2:24 AM Veronique Lefebure <
Veronique.Lefebure at cern.ch> wrote:

> Many thanks for these interesting hints!
> A last question then: how do you notify KEA processes (kea-dhcp4,
> kea-dhcp6) in case you modify any of you json files ? with a "reload"
> command ?
> Thanks,
> Veronique
> ------------------------------
> *From:* Dan Oachs <doachs at gac.edu>
> *Sent:* Thursday, November 17, 2022 8:36 PM
> *To:* Veronique Lefebure <Veronique.Lefebure at cern.ch>
> *Cc:* kea-users at lists.isc.org <kea-users at lists.isc.org>
> *Subject:* Re: [Kea-users] How to best update the KEA configuration on a
> HA hot-standby KEA setup
>
> The great thing about Kea is that it is very flexible and you can make it
> work in a wide variety of ways and find the setup that works best for your
> situation.
>
> In our case we have a hybrid setup.  The kea-dhcp4.conf file has all the
> global settings, and we define the hosts-database for storing host
> reservations.  We also break out all the subnet config into a separate
> subnets.json file and have the main file include that.
>
> We update the database directly from our own registration system, which is
> not recommended, but works fo us.  We chose not to pay for the host
> commands hook library that is required to use the api example you
> mentioned.
>
> I am pretty sure that you can do almost everything in the database that
> you can do in the config file, but are only using the database to store the
> host information.  I do see tables in the database that start with
> dhcp4_client_class which would lead me to believe that you can do what you
> want with the database configuration.
>
> --Dan
>
>
> On Thu, Nov 17, 2022 at 9:48 AM Veronique Lefebure <
> Veronique.Lefebure at cern.ch> wrote:
>
> Thanks Dan!
>
>
> So you have a hybrid configuration ?
> What do you mean by "main configuration" ? Topology (shared-networks and
> subnets) in json file and host-reservations in a database ?
> Do you update the database using "reservation-add"  (
> https://kea.readthedocs.io/en/latest/api.html?highlight=host%20reservation#reservation-add )
> ?
>
> We have client classes with a test expression that depends on the mac
> addresses of the clients.
> Can these classes be stored in the database as well ?
>
> Thanks,
> Veronique
>
>
> ------------------------------
> *From:* Dan Oachs <doachs at gac.edu>
> *Sent:* Thursday, November 17, 2022 4:20 PM
> *To:* Veronique Lefebure <Veronique.Lefebure at cern.ch>
> *Cc:* kea-users at lists.isc.org <kea-users at lists.isc.org>
> *Subject:* Re: [Kea-users] How to best update the KEA configuration on a
> HA hot-standby KEA setup
>
> We also have all the main configuration in plain json files.  Like you, we
> require hosts on some of our networks to be registered.  Our registration
> system stores the MAC addresses in the Kea database.  For the past year or
> so, this has worked really well for us.
>
> I would highly suggest looking into storing the MAC addresses in a
> database so you don't need to reload kea for every change.  You don't need
> to use the database for anything else if you don't want to.   This can also
> be done without any of the extra hook libraries that cost money.
>
> --Dan
>
>
>
> On Thu, Nov 17, 2022 at 2:19 AM Veronique Lefebure <
> Veronique.Lefebure at cern.ch> wrote:
>
> Hi,
>
> We don't use any database for storing the KEA configuration: we use plain
> json configuration files.
> We need to update the configuration very regularly because we allow only
> known clients (pre-registered mac addresses), hence the list of
> host-reservations is quite volatile.
>
> Véronique
> ------------------------------
> *From:* Dan Oachs <doachs at gac.edu>
> *Sent:* Wednesday, November 16, 2022 6:31 PM
> *To:* Veronique Lefebure <Veronique.Lefebure at cern.ch>
> *Cc:* kea-users at lists.isc.org <kea-users at lists.isc.org>
> *Subject:* Re: [Kea-users] How to best update the KEA configuration on a
> HA hot-standby KEA setup
>
> I am curious why you are updating the config every 5 minutes.   We used to
> do that with our old DHCP server, but with Kea we moved to storing
> reservations in a database.  That way we rarely need to make changes to the
> actual Kea configuration that would necessitate a reload of the config.
>
> --Dan
>
>
> On Wed, Nov 16, 2022 at 10:27 AM Veronique Lefebure <
> Veronique.Lefebure at cern.ch> wrote:
>
> Hi,
>
> When running KEA on one single server, (no HA), and updating the KEA dhcp
> configuration file every 5 minute, using "config-set"
>
> https://kea.readthedocs.io/en/latest/arm/ctrl-channel.html?highlight=config-set#the-config-set-command
>  ,
> we can see that KEA does not reply to the DHCP requests during 30-35
> seconds while "config-set" is running.
>
> Is it expected ?
> If yes, if we add a second server in a HA hot-standby mode, can we expect
> it to answer to the DHCP requests while the first server is busy with
> config-set ?
> If yes, we need to update the second server asynchronously with respect to
> the first one, else they would both be busy with "config-set" at the same
> time.
>
> I would be interested to know how people are updating the KEA DHCP
> configuration in a HA hot-standby setup.
>
> Thanks,
> Veronique
>
> --
> ISC funds the development of this software with paid support
> subscriptions. Contact us at https://www.isc.org/contact/ for more
> information.
>
> To unsubscribe visit https://lists.isc.org/mailman/listinfo/kea-users.
>
> Kea-users mailing list
> Kea-users at lists.isc.org
> https://lists.isc.org/mailman/listinfo/kea-users
>
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.isc.org/pipermail/kea-users/attachments/20221118/68b32137/attachment.htm>