If you use https to protect traffic between esjs client and the nodes in your cluster then you also can't use sniffing. This is because we use the /_nodes/_all/clear output to populate the connection pool and that API does not know that the nodes speak HTTPS at all. This change implements the config.sniffedNodesProtocol to fix this.
As it is implemented here, the sniffedNodesProtocol can be set to a string which will be used as the protocol configuration for each Host object created durring sniffing, plain and simple. The default value for this configuration depends on the hosts initially passed to the client, if all of the nodes have the same protocol that protocol is used. If your nodes list is empty or there is a mixture of protocols in this list then "http" is used, as it is the default protocol for each host.
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