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

[Veronique Lefebure]

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<mailto: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<mailto:doachs at gac.edu>>
Sent: Wednesday, November 16, 2022 6:31 PM
To: Veronique Lefebure <Veronique.Lefebure at cern.ch<mailto:Veronique.Lefebure at cern.ch>>
Cc: kea-users at lists.isc.org<mailto:kea-users at lists.isc.org> <kea-users at lists.isc.org<mailto: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<mailto: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

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