consul-replicate Many-Many DC replication

[hashicorp]

consul-replicate Many-Many DC replication

[armon]

The design of consul-replicate is such that it is only suited for master/slave replication.
This means a single datacenter should be considered the source of truth and the “master”,
from which all other DCs replicate keys.

As a result, the replication complexity is only N, since each slave is directly replicating from
the master. This means you get a “star” topology, with the master in the center.

Each datacenter uses an elected leader to serialize writes so there is never a multi-version
conflict. Because there is no coordination between datacenters for writes, there is no way
to reconcile conflicting writes. If key “test” has value “foo” in DC1 and “bar” in DC2 there
is no way for active-active replication to determine the correct value without substantial
changes to Consul.