Although MGR will use the channel Slave, but only use this thread of execution channel (Applier Thread) to perform Binlog Event, we did not use this channel to transmit Binlog Event. MGR did not use Binlog Event asynchronous replication transport mechanism, nor use MySQL service port for communication. MGR creates a separate TCP to the communication port, Group Replication MySQL server on each plug connected together through this port, direct communication between any two.
Transmission Binlog Event is not as asynchronous replication that is transmitted between the simple point to point. MGR during data transmission using a protocol Paxos. Paxos protocol to ensure consistency and atomicity of data transmission. MGR protocol based on Paxos build a distributed state machine replication mechanism, which is multi-master replication of core technology. This technology MGR brings three main advantages are as follows.
In 1.MGR split brain phenomenon it does not occur (but note that the case of network partitions that may occur, MGR according to the parameters group_replication_unreachable_majority_timeout = 0 / N setting different behavior is slightly different).
2.MGR good redundancy, to ensure at least Binlog Event is copied to more than half of its members, at the same time as long as no more than half the members of downtime will not cause data loss.
3.MGR also ensure long Binlog Event is not transmitted to more than half of the members, local members will not Binlog Event transaction documents and submit written Binlog affairs, so as to ensure no on-line members of the group will not have downtime on the server existing data. Therefore, the downtime server restarts, the need for special handling may join the group.