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Re: Why openshift requires DNS server



> Why does separate dns server need? Could kube-dns be used?

kube-dns is actually a separate dns server as well. Openshift's DNS implementation resolves some of the scalability issues kube-dns has and is preferred


On Jul 13, 2017, at 6:20 AM, Haoran Wang <haowang redhat com> wrote:

Hi,
1. when you setup your cluster, you will have some node that running a router pod,and  you need have a subdomain for your cluster, for example, you cluster will use product.example.com, so you need the DNS server setting forward the request with this DNS name prefix product.example.com to the router node.

2. Assume create a project named test, and  you deploy an app to the openshift cluster, you need create a route [1] for external access,  after you do that, the url you can be access is by test.product.example.com.  when you access the your app from outside, the general flow will be:

1. public dns server redirect you to your DNS server
2. Your dns server forward your request to one of the  node which have openshift router pod deployed
3. the router pod(it's running haproxy by default) will forward the request to the running pods

Hope this can help you. :)



Regards, 
Haoran Wang

OpenShift QE
IRC: haowang
Raycom office - Red Hat China                                                            
Direct: +86 10 65339430(ext-8389430) 

On Thu, Jul 13, 2017 at 5:47 PM, bmeng <bmeng redhat com> wrote:

AFAIK, the kube-dns resolve the service-names inside the cluster.

The dns server required by OpenShift gives the applications external accessibility.

With the dns resolution and the route you created for your application, you can access your web application anywhere.


On 07/13/2017 05:09 PM, Yu Wei wrote:

Hi,

I'm learning OpenShift by setting up cluster with VMs.

From the document, some content about DNS is as below,

OpenShift Origin requires a fully functional DNS server in the environment. This is ideally a separate host running DNS software and can provide name resolution to hosts and containers running on the platform.


Why does separate dns server need? Could kub-dns be used?


Thanks,

Jared, (韦煜)
Software developer
Interested in open source software, big data, Linux



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