Access to docker containers via coredns and coredns-dockerdiscovery plugin for development env

Receipt dns

Install coredns
Build images with coredns & dockerdiscovery plugin

One way

git clone git@github.com:kevinjqiu/coredns-dockerdiscovery.git  или go get github.com:kevinjqiu/coredns-dockerdiscovery.git
cd coredns-dockerdiscovery или cd ~/go/src/kevinjqiu/coredns-dockerdiscovery.git
docker build -t coredns-dockerdiscovery .

Create `Corefile`

skyeng.loc:53 {
    docker unix:///var/run/docker.sock {
        network_aliases skyeng_network
    }
    log
}

Start coredns with static assigned ip. For do it to indicate `--network` as any network for add ip

docker run -v /var/run/docker.sock:/var/run/docker.sock -v ${HOME}/Corefile:/coredns/Corefile --network skyeng_network --ip 172.19.5.5 --name=coredns --restart=unless-stopped -d coredns-dockerdiscovery -conf /coredns/Corefile

If you compiled binery file 

docker run -v /var/run/docker.sock:/var/run/docker.sock -v ${PWD}/coredns:/coredns -v ${HOME}/Corefile:/Corefile --name=coredns --restart=unless-stopped --network=skyeng_network --ip=172.18.5.5 -d alpine /coredns

Check out 

dig @172.19.5.5 postgres.e-api.skyeng.loc

Add our dns server's ip to system


echo "nameserver 172.19.5.5" | sudo tee --append /etc/resolvconf/resolv.conf.d/tail
sudo resolvconf -u

# possible you need install resolvconf (https://en.wikipedia.org/wiki/Resolvconf)
sudo apt install resolvconf

Check out

dig postgres.e-api.skyeng.loc

After manipulation with containers dns reply wrong ip

Sometimes it will be not avaliable or response contents not actual dns record. One of reasons is ttl not expired yet
You can cear resolve cache or reduce ttl

sudo systemd-resolve --flush-caches

Desirable reduce TTL by write cache directive in Corefile.
https://coredns.io/plugins/cache

Possible problems

Same topic https://github.com/jderusse/docker-dns-gen/issues/21

Internal dns inside containers stop work well.
Solution

I fixed it by adding this { "dns": ["8.8.8.8", "8.8.4.4"] } in /etc/docker/daemon.json
systemctl restart docker