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ILM shrink Action should pick only highest version nodes #41879
One of the steps in the ILM shrink action picks a random nodes with the current allocation rules and creates an allocation rule to require the shard are allocated on that node. This is necessary as a copy of each shard needs to be on the same node in order to perform the shrink operation.
When picking the random node ILM should consider the versions of the nodes and pick a node with the highest version. This will mean in a mixed cluster scenario ILM does not get into a deadlock situation where some shards are on a node with a higher version than the random node thats picked and therefore cannot be allocated to the randomly picked node (because we don't let shards move to an earlier versioned node)