Multiple coordinating nodes

[jwlee]

Quick question on the multiple coordinating nodes. Based on the document any nodes that are set to false to the node.master, node.data and node.ingest become the coordinating nodes.

If you have multiple coordinating nodes how are the requests handled? Does it implement round-robin to choose which coordinating node to handle the request? If so, how are the distributing the requests work? For example, if you have two requests that ask for the same document id, do each coordinating node communicate each other and distribute the requests to different shards?

My concern to this is if coordinating nodes handle the same requests on the same document id, it will keep stress on the same shards since each coordinating nodes are not aware of the requests that they individually handling.

Any inputs are appreciated. Thanks.

[DavidTurner]

@jwlee

If you have multiple coordinating nodes how are the requests handled?

Each coordinating node handles the requests it receives independently of the other coordinating nodes.

@jwlee

For example, if you have two requests that ask for the same document id, do each coordinating node communicate each other and distribute the requests to different shards?

No, there is no such communication. In practice this doesn't matter much, since the coordinating nodes each independently spread their load across all the available shards. If it does matter, then you can use adaptive replica selection to direct load to the more lightly-loaded replicas.