ML Architecture

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aakashali
Posts: 6
Joined: Mon Jun 08, 2020 10:26 am

ML Architecture

Post by aakashali »

How would MarkLogic determine the number nodes for your cluster to have a quorum and can we derive a formula for it ?

amitgope
Posts: 21
Joined: Thu Oct 01, 2020 4:10 pm

Re: ML Architecture

Post by amitgope »

Nodes communicate amongst themselves using heartbeat. If a node stops responding to a heartbeat this means that the node may be down.

To vote a node out of the cluster, there must be a quorum of nodes voting to remove a node. A quorum occurs more than 50% of the total number of nodes in the cluster (including any nodes that are down) vote the same way. Therefore, you need at least 3 nodes in the cluster to reach a quorum. The voting that each host performs is done based on how long it has been since it last had a heartbeat from the other node. If at half or more of the nodes in the cluster determine that a node is down, then that node is disconnected from the cluster. The wait time for a host to be disconnected from the cluster is typically considerably longer than the time for restarting a host, so restarts should not cause hosts to be disconnected from the cluster (and therefore they should not cause forests to fail over).

For failover to occur, you must have a quorum of particpant nodes (defined as "n/2 + 1").

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