Add more description of how the operator works #164
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* README.md: Mention that the operator allows some Corefile configuration. Expand the "How it works" section.
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| The DaemonSet's pod template specifies a "dns" container with CoreDNS and a "dns-node-resolver" container with a process that adds the cluster image registry service's DNS name to the host node's `/etc/hosts` file (see below). | ||
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| In order to resolve cluster service DNS names, the operator configures CoreDNS with the [kubernetes plugin](https://coredns.io/plugins/kubernetes/). This plugin resolves DNS names of the form `<service name>.<namespace>.svc.cluster.local` to the identified Service's corresponding endpoints. |
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The plugin also resolves pod names. For example:
$ oc get po/nginx -o wide
NAME READY STATUS RESTARTS AGE IP NODE NOMINATED NODE READINESS GATES
nginx 1/1 Running 0 6m31s 10.128.2.29 ip-10-0-139-148.us-west-2.compute.internal <none> <none>
$ oc exec -ti dnsutils -- nslookup 10-128-2-29.default.pod.cluster.local
Server: 172.30.0.10
Address: 172.30.0.10#53
Name: 10-128-2-29.default.pod.cluster.local
Address: 10.128.2.29
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| In order to resolve external DNS names, the operator configures CoreDNS to forward to the upstream name servers configured in the node host's `/etc/resolv.conf` (typically these name servers come from DHCP or are injected into a custom VM image). The operator allows the user to configure additional upstreams to use for specific zones; see <https://github.com/openshift/enhancements/blob/master/enhancements/dns/plugins.md>. | ||
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| The operator also creates a Service with a fixed IP address. This address is derived from the service network CIDR, namely by taking the tenth address in the address space. For example, if the service network CIDR is 172.30.0.0/16, then the DNS service's address is 172.30.0.10. |
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I think an example will help:
$ oc get network/cluster -o jsonpath='{.status.serviceNetwork[0]}'
172.30.0.0/16
| @@ -5,11 +5,30 @@ The DNS Operator deploys and manages [CoreDNS](https://coredns.io) to provide a | |||
| The operator tries to be useful out of the box by creating a working default deployment based on the cluster's configuration. | |||
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| * The default cluster domain is `cluster.local`. | |||
| * Configuration of the CoreDNS [Corefile](https://coredns.io/manual/toc/#configuration) or [kubernetes plugin](https://coredns.io/plugins/kubernetes/) is not yet supported. | |||
| * Limited configuration of the CoreDNS [Corefile](https://coredns.io/manual/toc/#configuration) or [kubernetes plugin](https://coredns.io/plugins/kubernetes/) is supported. | |||
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@Miciah I'm confused by or in this sentence. The k8s plugin is a subset of the corefile config, right?
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Right, I should change "or" to "and". Would that be sufficient?
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I would keep the bullet as:
Limited configuration of the CoreDNS Corefile.
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/lgtm |
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[APPROVALNOTIFIER] This PR is APPROVED This pull-request has been approved by: ironcladlou, Miciah The full list of commands accepted by this bot can be found here. The pull request process is described here
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
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/retest Please review the full test history for this PR and help us cut down flakes. |
README.md: Mention that the operator allows someCorefileconfiguration. Expand the "How it works" section.