Paxos Principal node


#1

Hello,

I’ve question regarding “Paxos Principal node”. Under the info Header in the link below, there is a sentence goes that: “You will also notice that one node name is always green, this node is the node expected to be the Paxos Principal node.”. I couldn’t find any more info about “Paxos Principal node”, could someone explain it in details? do we have a specific node like the name node in hadoop? How is it relate to Paxos protocols?

https://www.aerospike.com/docs/tools/asadm/user_guide/cluster_mode_guide#info

Thanks,


#2

Paxos plays its part in establishing cluster membership. Once all nodes agree on who is in the cluster (this is a very brief initial cluster bring up or cluster change period), there is no “master” for database operations. Hadoop name node has the information about where the data is in the hadoop cluster nodes - so all hadoop clients have to first go to the Hadoop name node. Not so in Aerospike. Aerospike Client knows which node has the its data and goes directly to the node. Hadoop is Master-Slave, Aerospike is Shared-Nothing


#3

At a high level, this is simply the node that has the ‘highest’ node id (sorted alphabetically) across all nodes in the cluster and to which all nodes send ‘partition sync’ requests (providing which partitions/versions they own) when the cluster forms (or re-forms) in order to get migrations (rebalancing) going.

In short, it only has some importance for the cluster to form and migrations to start, but other than that, it doesn’t play any role for the data during normal operations for the cluster.