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We also have the required settings in the node.attr.rack setting, which is documented in the doc, Configuring Elasticsearch.
The attribute name rack or rack_id or availabilityzone does not matter as long as cluster.routing.allocation.awareness.attributes: <name> is set along with node.attr.<name>.
The zone name uniquely identifies the rack or ESXi host with elasticsearch nodes in the same zone using the same value. You must do a rolling restart Rolling Restart of Elasticsearch - Swarm Documentation - Confluence (atlassian.net) of all your elasticsearch nodes after updating elasticsearch.yml, waiting for the shard reallocations to complete.