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I just started node1 as donor with ‘/etc/init.d/mysql start --wsrep-new-cluster’. Then started second node. and check "show status like 'wsrep%'" in mysql. but the second’s wsrep_local_index became 0 and first node became 1.

Also started third node and now first node became 2 and third node became 0.

Why donor node changed? I can’t understand. please help me.

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If you check official documentation you'll see this:

When using automatic donor selection, starting in Galera Cluster version 3.6, the cluster decides which state transfer method to use based on availability.

  • If there are no nodes available that can safely perform an incremental state transfer, the cluster defaults to a state snapshot transfer.
  • If there are nodes available that can safely perform an incremental state transfer, the cluster prefers a local node over remote nodes to serve as the donor.
  • If there are no local nodes available that can safely perform an incremental state transfer, the cluster chooses a remote node to serve as the donor.
  • Where there are several local or remote nodes available that can safely perform an incremental state transfer, the cluster chooses the node with the highest seqno to serve as the donor.
  • As I know donor node is first started node but it can be changed? why and how??? – user448347 Dec 15 '17 at 1:12
  • @user448347 yes, it could be changed manually or automatically. Here old post from Percona blog about it. – Alexander Tolkachev Dec 15 '17 at 9:49

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