node-dns

README

node-dns

node-dns is a simple local DNS server that can be deployed via kubernetes. It is specially built for using with KubeEdge nodes. node-dns only works for the very node only where it is running. You must ensure that your pods that want to communicate whith each other run on the exact same node.

Why?

When using KubeEdge, it is common for two pods running on the same node to need to communicate with each other. Due to the fact that containers running on the edge using KubeEdge cannot address each other with their container host names, they can't easily find them other than the using the IP address. However the IP address of the containers might not be known to other containers or change if a container dies and gets rescheduled. node-dns solves the problem of resolving a name with the container IP addresses in a very light weight way directly on the edge node.

How?

node-dns is deployed as DaemonSet on everye KubEdge node. node-dns gets it's information on how to resolve which host to its IP address by configuring and using a feed. A feed is a source for information to and could be implemented as e.g.

• the k8s api server
• scanning currently containers using a docker client. node-dns updates its feed every minute. This means that in the worst case the DNS resolution is possible after 60 seconds max. node-dns patches the hosts /etc/resolv.conf and makes it available to other containers.

Currently supported feeds

It might be possible to introduce more feeds, however currently supported is the k8s API feed only.

k8s API feed

The k8s API feed connects directly to the k8s API server (see configuration file), reads the podsList and looks at the pods labels. All pods with the label node-dns.host=<value> will be handeled by node-dns. The name name for the resolution is <containerName>.<value> where <value> is the value from the label node-dns.host.

Examples

See the examples/ directory for example manifest files on hwo to use the needed label.

Configuration

A valid configuration can look like this:

listeninterface: docker0
listenport: 53
resolvConf: /etc/resolv.conf
removeSearchDomains: true
feed:
  k8sapi:
    enabled: true
    uri: http://127.0.0.1:10550
    insecuretls: true
    token: ""