Due to a ransomware attack, the wiki was reverted to a July 2022 version. . We apologize for the lack of a more recent valid backup.
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Since v1.4 Hazelcast has been replaced by the Atomix framework. This change was motivated by managing the recovery from split-brain situations. Since Atomix is based on the RAFT consensus algorithm, the cluster must be composed by an odd number of member controller nodes. Previously supported 2- or 4-node deployments shall be replaced by 3- and 5-node deployments.
Device Mastership Management
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Given that a cluster splits into two of different sizes, the nodes in the smaller cluster will relinquish their roles, or, incapable of doing so, members of the larger cluster will force reelections for devices whose master nodes became part of the smaller cluster. The MastershipManager determines wether if whether it is in the minority or majority by querying the ClusterService.
The current Historically, the ONOS implementation (based on Hazelcast) does not handle the case where the partitions are equal in size, and both are still connected to the network. Since v1.4, the Atomix framework ensures that this situation would not occur, since the number of controller cluster members are always odd (usually 3 or 5).
Relation to the Device Subsystem
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