Negotiations
On startup, or whenever an active instance shuts down, the cluster instances negotiate to determine which one will be active.
Priority is given to the instance with the highest ID (as specified in
the instance_id
property in the
cluster
configuration object). If not all instances
are running during the negotiation process, however, then another
instance may be designated active instead.
If instance_id
s are not explicitly set, then
instances are assigned random IDs each time they are started. If
instances are regularly re-started, this introduces some randomness
with regard to which instance is given priority during negotiation.
After negotiation, all the non-active instances will enter the inactive state, in which they do not process any Content Store updates. If the active instance shuts down or disappears, the idle instances will re-enter negotiations to find a new active instance.