[Kea-users] Dropping the packets in load balancing

[Kraishak Mahtha]

Hi Peter,

ok, I tried this way stopping the kea-dhcp service on failover and see if
that will make a difference, and see if the client get able to get the ACK,

I have three doubts,
1)I stopped kea-DHCP on failover and it crossed the max-response-delay time
i.e 60000, and also it crosses the max-unacked-clients values too but
still, the failover state is showing as communication-recovery not sure
when it will change to partner-down state.
HA code snippet:
==============
       "hooks-libraries": [
        {
            "library": "/usr/local/kea/hooks/libdhcp_ha.so",
            "parameters": {"high-availability": [{
                "mode": "load-balancing",
                "heartbeat-delay": 10000,
                "trust-anchor": "",
                "multi-threading": {
                    "http-dedicated-listener": true,
                    "enable-multi-threading": true,
                    "http-client-threads": 4,
                    "http-listener-threads": 4
                },
                "max-response-delay": 60000,
                "cert-file": "",
                "this-server-name": "dhcp1",
                "max-ack-delay": 10000,
                "peers": [
                    {
                        "role": "primary",
                        "name": "dhcp1",
                        "auto-failover": true,
                        "url": "http://192.168.0.125:8001"
                    },
                    {
                        "role": "secondary",
                        "name": "dhcp2",
                        "auto-failover": true,
                        "url": "http://192.168.0.126:8001"
                    }
                ],
                "key-file": "",
                "max-unacked-clients": 13
            }]}
        },

   status get output:
=================
[root at dhcp1 ~]# echo '{"command":"status-get"}' | socat -
UNIX:/var/kea4-ctrl-socket | jq
{
  "arguments": {
    "high-availability": [
      {
        "ha-mode": "load-balancing",
        "ha-servers": {
          "local": {
            "role": "primary",
            "scopes": [
              "dhcp1"
            ],
            "state": "communication-recovery"
          },
          "remote": {
            "age": 4141,
            "analyzed-packets": 93,
            "communication-interrupted": true,
            "connecting-clients": 19,
            "in-touch": true,
            "last-scopes": [
              "dhcp2"
            ],
            "last-state": "unavailable",
            "role": "secondary",
            "unacked-clients": 1,
            "unacked-clients-left": 13
          }
        }
      }
    ],
    "multi-threading-enabled": true,
    "packet-queue-size": 7,
    "packet-queue-statistics": [
      1,
      0.954504,
      0.23734
    ],
    "pid": 14491,
    "reload": 4284,
    "sockets": {
      "status": "ready"
    },
    "thread-pool-size": 4,
    "uptime": 4284
  },
  "result": 0
}


2)Based on the hash value the kea-dhcp will decide which server to grant
leases but now even after kea-dhcp is down on failover the primary is not
able to give a lease, it completed the max-ack-delay duration too but still
it is dropping the packet
last,
3)Can we manually set the failover state to partner-down and is it
recommended?

Thanks
Kraishak

On Wed, May 10, 2023 at 1:05 PM Peter Davies <peterd at isc.org> wrote:

> Hi Kraishak,
>    This behaviour is expected when HA is configured in "load-balancing"
> mode.
>
> Under normal operations, the two Kea servers divide the clients between
> them.
>
> The server decides which clients they need to respond to based on a hash
> of the
> client identifier; this is often the client's Mac address. The split is
> 50/50.
>
> Kind Regards Peter
>
> ------------------------------
> *From: *"Kraishak Mahtha" <kraishak.edu at gmail.com>
> *To: *"Kea-users at lists.isc.org" <kea-users at lists.isc.org>
> *Sent: *Wednesday, 10 May, 2023 08:45:08
> *Subject: *[Kea-users] Dropping the packets in load balancing
>
> Hi all,
> I have configured the kea-HA in load-balancing mode, and I am testing the
> flow by hitting the discover packets only to the primary server using my
> lease test tool but I see a few of the packets get dropped or have not been
> seen.
>
>  When I see the log I see as:
> HA_BUFFER4_RECEIVE_NOT_FOR_US [hwtype=1 82:ff:ff:00:00:01],
> cid=[01:82:ff:ff:00:00:01], tid=0x29652559: dropping query to be processed
> by another server
>
> I have a few doubts about this
> 1)I have only 10 active leases in the given scope range and we still have
> so many free leases then why does the server drop the query and hand it
> over to its peer?
> 2)Do we need to add any parameters in the config file to make the kea-DHCP
> primary to forcefully check its all free available IPs?
>
> Thanks in advance
> Kraishak
>
>
> Attached are my kea-dhcp configs of primary and failover
>
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