We have more than 10 services who use es in different ways.
So each service connect to the cluster themselves.
That is, if i want to upgrade es to 6.0, we need to upgrade and test all the services at the same time, fully shutdown the cluster, deploy the new services, start the whole cluster and start the upgraded services.
This work seems so complex, and we can not make sure all the thing is right when upgrading.
Is there any other choice for us, so that we can upgrade es first, leaving the services running old version clients?