[Kea-users] High availability with a database cluster issue

[Sébastien Nauer]

Hello,

We are experiencing issues with configuring a KEA cluster in
high-availability mode with a GALERA Cluster database backend.

As we'd like to use the database cluster for managing leases
synchronization :

   - we configured KEA High Availability mode like this for disabling lease
   sync & update :

"high-availability": [
    {
        "this-server-name": "kea01",
        "mode": "load-balancing",
        "heartbeat-delay": 10000,
        "max-response-delay": 10000,
        "max-ack-delay": 5000,
        "max-unacked-clients": 5,
        "send-lease-updates": false,
        "sync-leases": false,
        "sync-page-limit": 10000,
        "sync-timeout": 30000,
        "multi-threading": {
            "enable-multi-threading": true,
            "http-dedicated-listener": true,
            "http-listener-threads": 0,
            "http-client-threads": 0
         },
        "peers": [
            {
                "name": "kea0&",
                "url": "http://1.2.3.4:8080/",
                "role": "primary",
                "auto-failover": true
            },
            {
                "name": "kea04",
                "url": "http://5.6.7.8:8080/",
                "role": "secondary",
                "auto-failover": true
            }
        ]
    }
]

   - we configured the lease database like this for connecting to the
   database cluster :

"lease-database": {
    "type": "mysql",
    "name": "kea",
    "user": "KEA_USER",
    "password": "KEA_PASSWORD",
    "host": "1.1.1.1",
    "max-reconnect-tries" : 10,
    "reconnect-wait-time" : 30000
},

   - we tried to connect to the database backend :
      - through a VIP with load balancing
      - through HAPROXY with / without load balancing
      -

When we start KEA service and the servers start, KEA logs show a lot of
DATABASE_MYSQL_FATAL_ERROR messages like this :

2025-01-07 16:18:42.483 ERROR [kea-dhcp4.database/4349.0x34cf8b308500]
DATABASE_MYSQL_FATAL_ERROR Unrecoverable MySQL error occurred: unable to
execute for <SELECT h.host_id, h.dhcp_identifier, h.dhcp_identifier_type,
h.dhcp4_subnet_id, h.dhcp6_subnet_id, h.ipv4_address, h.hostname,
h.dhcp4_client_classes, h.dhcp6_client_classes, h.user_context,
h.dhcp4_next_server, h.dhcp4_server_hostname, h.dhcp4_boot_file_name,
h.auth_key, o.option_id, o.code, o.value, o.formatted_value, o.space,
o.persistent, o.cancelled, o.user_context FROM hosts AS h LEFT JOIN
dhcp4_options AS o ON h.host_id = o.host_id WHERE h.dhcp4_subnet_id = ? AND
h.dhcp_identifier_type = ? AND h.dhcp_identifier = ? ORDER BY h.host_id,
o.option_id>, reason: Server has gone away (error code: 2006).
2025-01-07 16:18:43.533 INFO  [kea-dhcp4.dhcp4/4349.0x34cf8aa12000]
DHCP4_DB_RECONNECT_LOST_CONNECTION database connection lost.
2025-01-07 16:18:43.533 INFO  [kea-dhcp4.hosts/4349.0x34cf8aa12000]
DHCPSRV_MYSQL_HOST_DB opening MySQL hosts database: host=10.194.50.12
max-reconnect-tries=10 name=prod_kea password=*****
reconnect-wait-time=30000 type=mysql universe=4 user=keaCluster
2025-01-07 16:18:43.586 INFO  [kea-dhcp4.dhcp4/4349.0x34cf8aa12000]
DHCP4_DB_RECONNECT_SUCCEEDED database connection recovered.

As we noticed that the database connection is frequently lost for no
apparent reason we suspect that there is an issue with using persistent
database connections through a VIP with load balancing (maybe related to
multithreading also)

Has anyone successfully configured such a setup ? How ?
What do you suggest for avoiding this error message and configuring a high
availability DHCP cluster with a high availability database cluster ?

Any feedback from the community will be appreciated !
Kind regards



-- 

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*Sébastien NAUER <snauer at hotcity.lu>*| Technical Manager
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