After the primary Kea server has been added to Micetro, it acts as the primary mode of communication between Micetro and the High Availability (HA) cluster. All changes are written to this primary server, whose in-memory config is the single-source-of-truth for the configuration, and replication is handled accordingly. In the event of a failover, the secondary server assumes this role and any changes to the HA cluster should be made to it through Micetro.
- Normal operation
- When both the primary Kea server and all its secondary/backup partners in the
High Availability environment are running and accessible, Micetro reports the
Kea DHCP server as OK.
- Primary server offline
- If the primary server is offline or unavailable for any reason, e.g., reporting
itself in a disabled state, or becomes unreachable from Micetro, the
secondary/standby server will take over as the primary in Micetro. Micetro will
report the Kea DHCP service as Impaired. During this time, the
single-source-of-truth will be the in-memory config on the secondary/standby
server until connection to the primary server is re-established.
- Secondary/standby/backup server offline
- If any of the secondary/standby/backup servers are offline, replication to all
other servers will still occur, but Micetro will report the Kea DHCP service as
Impaired. When the affected secondary/standby/backup reports itself
as Active again, it will be automatically synchronized with the
single-source-of-truth configuration (the in-memory config of the primary Kea
server).
- Both primary and secondary/standby server offline
- If both primary and secondary/standby servers go offline, Micetro will report
the Kea DHCP service as Service down. All further operations will result
in an error reporting this downtime. All replication is stopped until either the
primary or the secondary/standby servers report themselves as Active. The
first server to become active will be the single-source-of-truth, but the
primary will always override any secondary/backup when it becomes active.
- DHCP server agent offline
- In the unlikely event that the DHCP Agent is offline, all Kea High Availability
information will be momentarily lost. Micetro will report the Kea DHCP service
as Unreachable. As soon as the Agent comes back online, Micetro Central
will attempt to reconnect to the preconfigured primary Kea DHCP server. After
reconnecting to the primary server, the configuration will be parsed again, the
High Availability setup detected, and replication between servers resumed.
Note: If the DHCP Agent goes offline while using the secondary/backup Kea server (because the primary server was down), the system will not be able to reconnect successfully. Because only the primary Kea server can be added to Micetro, a system administrator must reestablish the primary Kea server to a working state before the system will be able to reconnect.