In Kubernetes, if I run a Service Foo on every Node, and also Service Bar on every Node, i.e. with
DaemonSets. If a Pod from Service Foo needs to make a request to Service Bar, does Kubernetes networking magic optimise things so communication will be done within the same Node, i.e. without a external network call? Or will a random Pod Bar be picked meaning usually Bar will be on a different Node, so there will be a network hop?
Context to question: I'm thinking to run
CoreDNS as a
Daemonset, because with the cache plugin, I'm hoping most DNS queries will not need to use the network as there will always be a CoreDNS Pod co-located within the same Node and most requests will be cached. Currently we only run 3 CoreDNS pods and we have 12 Nodes and we see some DNS failures at times of network traffic surges - particularly during a deployment when lot of logging is done, which have to be shipped across the network to ElasticSearch.
In case specifics matter:
- The CoreDNS service runs as
- The services that use CoreDNS run as
- The Kubernetes cluster is AWS EKS, v1.14.9. Networking is done with the AWS VPC CNI.