Kubernetes集群内部负载平衡

Question

Playing a bit with Kubernetes (v1.3.2) I'm checking the ability to load balance calls inside the cluster (3 on-premise CentOS 7 VMs).
If I understand correctly the documentation in http://kubernetes.io/docs/user-guide/services/ 'Virtual IPs and service proxies' paragraph, and as I see in my tests, the load balance is per node (VM). Ie, if I have a cluster of 3 VMs and deployed a service with 6 pods (2 per VM), the load balancing will only be between the pods of the same VM which is somehow disappointing.
At least this is what I see in my tests: Calling the service from within the cluster using the service's ClusterIP, will load-balance between the 2 pods that reside in the same VM that the call was sent from. (BTW, the same goes when calling the service from out of the cluster (using NodePort) and then the request will load-balance between the 2 pods that reside in the VM which was the request target IP address).
Is the above correct?
If yes, how can I make internal cluster calls load-balance between all the 6 replicas? (Must I employ a load balancer like nginx for this?)

Answer 1

No, the statement is not correct. The loadbalancing should be across nodes (VMs). This demo demonstrates it. I have run this demo on a k8s cluster with 3 nodes on gce. It first creates a service with 5 backend pods, then it ssh into one gce node and visits the service.ClusterIP, and the traffic is loadbalanced to all 5 pods. I see you have another question "not unique ip per pod" open, it seems you hadn't set up your cluster network properly, which might caused what you observed.

Answer 2

在您的情况下，每个节点都将运行服务的副本-并在各个节点之间实现负载平衡。