I was trying to understand how Raft algorithm overcomes FLP theorem. For FLP to be valid, consensus algorithm should be deterministic, termination and asynchronous. As the PhD dissertation on the Raft consensus algorithm says
Unfortunately, it is difficult to put a bound on the time or number of messages leader election will take. According to the FLP impossibility result [28], no fault-tolerant consensus protocol can deterministically terminate in a purely asynchronous model. This manifests itself in split votes in Raft, which can potentially impede progress repeatedly during leader election. Raft also makes use of randomized timeouts during leader election, which makes its analysis probabilistic. Thus, we can only say that leader election performs well with high likelihood, and even then only under various assumptions. For example, servers must choose timeouts from a random distribution (they are not somehow synchronized), clocks must proceed at about the same rates, and servers and networks must be timely (or stopped). If these assumptions are not met for some period of time, the cluster might not be able to elect a leader during that period (though safety will always be maintained).
So even if it is difficult to put a bound on the time or number of messages leader election will take, is it possible to guarantee that in all cases eventually a leader will be elected? If not, in which case the leader election will never terminate?
