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8ee88a9d8a
Introduce a special state machine used to to find a leader of an existing Raft cluster or create a new cluster. This state machine should be used when a new Scylla node has no persisted Raft Group 0 configuration. The algorithm is initialized with a list of seed IP addresses, IP address of this server, and, this server's Raft server id. The IP addresses are used to construct an initial list of peers. Then, the algorithm tries to contact each peer (excluding self) from its peer list and share the peer list with this peer, as well as get the peer's peer list. If this peer is already part of some Raft cluster, this information is also shared. On a response from a peer, the current peer's peer list is updated. The algorithm stops when all peers have exchanged peer information or one of the peers responds with id of a Raft group and Raft server address of the group leader. (If any of the peers fails to respond, the algorithm re-tries ad infinitum with a timeout). More formally, the algorithm stops when one of the following is true: - it finds an instance with initialized Raft Group 0, with a leader - all the peers have been contacted, and this server's Raft server id is the smallest among all contacted peers.