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feat: turn nodelocaldns image to svg

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This commit is contained in:
Bradley Weston
2020-05-29 10:28:47 +01:00
parent 6874e48e3a
commit 85c8fd8e1f
4 changed files with 24 additions and 21 deletions
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content/en/docs/tasks/administer-cluster/nodelocaldns.md
+17 -17
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@@ -6,7 +6,7 @@ reviewers:
title: Using NodeLocal DNSCache in Kubernetes clusters
content_template: templates/task
---
{{% capture overview %}}
{{< feature-state for_k8s_version="v1.18" state="stable" >}}
This page provides an overview of NodeLocal DNSCache feature in Kubernetes.
@@ -27,7 +27,7 @@ NodeLocal DNSCache improves Cluster DNS performance by running a dns caching age
## Motivation
* With the current DNS architecture, it is possible that Pods with the highest DNS QPS have to reach out to a different node, if there is no local kube-dns/CoreDNS instance.
* With the current DNS architecture, it is possible that Pods with the highest DNS QPS have to reach out to a different node, if there is no local kube-dns/CoreDNS instance.
Having a local cache will help improve the latency in such scenarios.
* Skipping iptables DNAT and connection tracking will help reduce [conntrack races](https://github.com/kubernetes/kubernetes/issues/56903) and avoid UDP DNS entries filling up conntrack table.
@@ -45,7 +45,7 @@ Having a local cache will help improve the latency in such scenarios.
This is the path followed by DNS Queries after NodeLocal DNSCache is enabled:
{{< figure src="/images/docs/nodelocaldns.jpg" alt="NodeLocal DNSCache flow" title="Nodelocal DNSCache flow" caption="This image shows how NodeLocal DNSCache handles DNS queries." >}}
{{< figure src="/images/docs/nodelocaldns.svg" alt="NodeLocal DNSCache flow" title="Nodelocal DNSCache flow" caption="This image shows how NodeLocal DNSCache handles DNS queries." >}}
## Configuration
{{< note >}} The local listen IP address for NodeLocal DNSCache can be any IP in the 169.254.20.0/16 space or any other IP address that can be guaranteed to not collide with any existing IP. This document uses 169.254.20.10 as an example.
@@ -54,33 +54,33 @@ This is the path followed by DNS Queries after NodeLocal DNSCache is enabled:
This feature can be enabled using the following steps:
* Prepare a manifest similar to the sample [`nodelocaldns.yaml`](https://github.com/kubernetes/kubernetes/blob/master/cluster/addons/dns/nodelocaldns/nodelocaldns.yaml) and save it as `nodelocaldns.yaml.`
* Substitute the variables in the manifest with the right values:
* Substitute the variables in the manifest with the right values:
* kubedns=`kubectl get svc kube-dns -n kube-system -o jsonpath={.spec.clusterIP}`
* domain=`<cluster-domain>`
* kubedns=`kubectl get svc kube-dns -n kube-system -o jsonpath={.spec.clusterIP}`
* domain=`<cluster-domain>`
* localdns=`<node-local-address>`
`<cluster-domain>` is "cluster.local" by default. `<node-local-address>` is the local listen IP address chosen for NodeLocal DNSCache.
* If kube-proxy is running in IPTABLES mode:
* If kube-proxy is running in IPTABLES mode:
``` bash
sed -i "s/__PILLAR__LOCAL__DNS__/$localdns/g; s/__PILLAR__DNS__DOMAIN__/$domain/g; s/__PILLAR__DNS__SERVER__/$kubedns/g" nodelocaldns.yaml
```
`__PILLAR__CLUSTER__DNS__` and `__PILLAR__UPSTREAM__SERVERS__` will be populated by the node-local-dns pods.
`__PILLAR__CLUSTER__DNS__` and `__PILLAR__UPSTREAM__SERVERS__` will be populated by the node-local-dns pods.
In this mode, node-local-dns pods listen on both the kube-dns service IP as well as `<node-local-address>`, so pods can lookup DNS records using either IP address.
* If kube-proxy is running in IPVS mode:
* If kube-proxy is running in IPVS mode:
``` bash
sed -i "s/__PILLAR__LOCAL__DNS__/$localdns/g; s/__PILLAR__DNS__DOMAIN__/$domain/g; s/__PILLAR__DNS__SERVER__//g; s/__PILLAR__CLUSTER__DNS__/$kubedns/g" nodelocaldns.yaml
```
In this mode, node-local-dns pods listen only on `<node-local-address>`. The node-local-dns interface cannot bind the kube-dns cluster IP since the interface used for IPVS loadbalancing already uses this address.
In this mode, node-local-dns pods listen only on `<node-local-address>`. The node-local-dns interface cannot bind the kube-dns cluster IP since the interface used for IPVS loadbalancing already uses this address.
`__PILLAR__UPSTREAM__SERVERS__` will be populated by the node-local-dns pods.
* Run `kubectl create -f nodelocaldns.yaml`
* If using kube-proxy in IPVS mode, `--cluster-dns` flag to kubelet needs to be modified to use `<node-local-address>` that NodeLocal DNSCache is listening on.
Otherwise, there is no need to modify the value of the `--cluster-dns` flag, since NodeLocal DNSCache listens on both the kube-dns service IP as well as `<node-local-address>`.