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https://github.com/contentful-labs/coredns-nodecache
Nodelocal DNS implementation as a CoreDNS plugin
https://github.com/contentful-labs/coredns-nodecache
coredns-nodecache coredns-plugin dns kubernetes node-local
Last synced: 3 months ago
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Nodelocal DNS implementation as a CoreDNS plugin
- Host: GitHub
- URL: https://github.com/contentful-labs/coredns-nodecache
- Owner: contentful-labs
- License: apache-2.0
- Created: 2019-07-18T16:04:23.000Z (almost 5 years ago)
- Default Branch: master
- Last Pushed: 2023-03-23T09:38:09.000Z (over 1 year ago)
- Last Synced: 2023-08-20T06:11:09.131Z (10 months ago)
- Topics: coredns-nodecache, coredns-plugin, dns, kubernetes, node-local
- Language: Go
- Homepage:
- Size: 7.66 MB
- Stars: 73
- Watchers: 18
- Forks: 12
- Open Issues: 6
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Lists
- awesome-stars - contentful-labs/coredns-nodecache - Nodelocal DNS implementation as a CoreDNS plugin (Go)
README
# Coredns-nodecache [](https://circleci.com/gh/contentful-labs/coredns-nodecache)
The Kubernetes [Node-local dns](https://github.com/kubernetes/kubernetes/tree/master/cluster/addons/dns/nodelocaldns)
add-on proposes running a DNS caching server on all of a Kubernetes cluster's nodes. The suggested caching server is
[node-cache](https://github.com/kubernetes/dns/tree/master/cmd/node-cache), a thin wrapper around CoreDNS, that
handles the setup & teardown of the dummy network interface & associated IPTables rules.
**Coredns-nodecache** is an attempt to implement node-cache as a CoreDNS plugin, rather than a wrapper. The motivations
for this are:
* the implementation relies only on CoreDNS Plugin API, which should be backward-compatible from version to version.
This should make using the latest version of CoreDNS easier (see
[kubernetes/dns #306](https://github.com/kubernetes/dns/issues/306))
* the configuration of nodecache would be done in the CoreDNS configuration file, instead of being split between
the Corefile and command-line parameters.
Additionally, coredns-nodecache can provide a **high-availability** setup for Node-local.
### Plugin configuration
An image is available on DockerHub: https://hub.docker.com/r/contentful/coredns-nodecache
Configuration is done by adding `nodecache` to configuration blocks in your CoreDNS configuration file.
```
nodecache [skipteardown]
```
* **skipteardown**: skips removing the iptables and dummy network interface on shutdown. This is especially useful
for high-availability setups.
As the following example shows, you can use the directive in several blocks. For each block, coredns-nodecache will
add the "bind" address to the dummy interface, and create iptable rules for the IP:PORT.
```
.:5300 {
bind 168.255.10.20
nodecache
forward . 1.1.1.1:53 {
force_tcp
}
}
.:5301 {
bind 168.255.10.25
nodecache
forward . 1.1.1.1:53 {
force_tcp
}
}
```
### High-availability setup
CoreDNS & coredns-nodecache can provide a high-availbility setup for Kubernetes Node-local, using two separate Daemonsets & SO_REUSEPORT.
An example deployment is provided in [k8s/node-local-ha.yaml](k8s/node-local-ha.yaml).
### Development
Checkout this repository & CoreDNS in your GOPATH. in the CoreDNS repository, in plugin.cfg, add the following line:
```nodecache:github.com/contentful-labs/coredns-nodecache```
Then at the end of go.mod:
```replace github.com/contentful-labs/coredns-nodecache => ../../contentful-labs/coredns-nodecache```
*make* should build CoreDNS and include the coredns-nodecache plugin.
```
./coredns -plugins
[...]
dns.metadata
dns.nodecache
dns.nsid
[...]
```