coredns-dockerdiscovery
Docker discovery plugin for coredns
Name
dockerdiscovery - add/remove DNS records for docker containers.
Syntax
docker [DOCKER_ENDPOINT] {
domain DOMAIN_NAME
hostname_domain HOSTNAME_DOMAIN_NAME
network_aliases DOCKER_NETWORK
label LABEL
compose_domain COMPOSE_DOMAIN_NAME
}
DOCKER_ENDPOINT: the path to the docker socket. If unspecified, defaults tounix:///var/run/docker.sock. It can also be TCP socket, such astcp://127.0.0.1:999.DOMAIN_NAME: the name of the domain for container name, e.g. whenDOMAIN_NAMEisdocker.loc, your container withmy-nginx(as subdomain) name will be assigned the domain name:my-nginx.docker.locHOSTNAME_DOMAIN_NAME: the name of the domain for hostname. Work same asDOMAIN_NAMEfor hostname.COMPOSE_DOMAIN_NAME: the name of the domain when it is determined the container is managed by docker-compose. e.g. for a compose project of "internal" and service of "nginx", ifCOMPOSE_DOMAIN_NAMEiscompose.locthe fqdn will benginx.internal.compose.locDOCKER_NETWORK: the name of the docker network. Resolve directly by network aliases (like internal docker dns resolve host by aliases whole network)LABEL: container label of resolving host (by default enable and equalscoredns.dockerdiscovery.host)
How To Build
GO111MODULE=on go get -u github.com/coredns/coredns
GO111MODULE=on go get github.com/kevinjqiu/coredns-dockerdiscovery
cd ~/go/src/github.com/coredns/coredns
echo "docker:github.com/kevinjqiu/coredns-dockerdiscovery" >> plugin.cfg
cat plugin.cfg | uniq > plugin.cfg.tmp
mv plugin.cfg.tmp plugin.cfg
make all
~/go/src/github.com/coredns/coredns/coredns --version
Alternatively, you can use the following manual steps:
- Checkout coredns:
go get github.com/coredns/coredns. cd $GOPATH/src/github.com/coredns/corednsecho "docker:github.com/kevinjqiu/coredns-dockerdiscovery" >> plugin.cfggo generatemake
Alternatively, run insider docker container
docker build -t coredns-dockerdiscovery .
docker run --rm -v ${PWD}/Corefile:/etc/Corefile -v /var/run/docker.sock:/var/run/docker.sock -p 15353:15353/udp coredns-dockerdiscovery -conf /etc/Corefile
Run tests
go test -v
Example
Corefile:
.:15353 {
docker unix:///var/run/docker.sock {
domain docker.loc
hostname_domain docker-host.loc
}
log
}
Start CoreDNS:
$ ./coredns
.:15353
2018/04/26 22:36:32 [docker] start
2018/04/26 22:36:32 [INFO] CoreDNS-1.1.1
2018/04/26 22:36:32 [INFO] linux/amd64, go1.10.1,
CoreDNS-1.1.1
Start a docker container:
$ docker run -d --name my-alpine --hostname alpine alpine sleep 1000
78c2a06ef2a9b63df857b7985468f7310bba0d9ea4d0d2629343aff4fd171861
Use CoreDNS as your resolver to resolve the my-alpine.docker.loc or alpine.docker-host.loc:
$ dig @localhost -p 15353 my-alpine.docker.loc
; <<>> DiG 9.10.3-P4-Ubuntu <<>> @localhost -p 15353 my-alpine.docker.loc
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 61786
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;my-alpine.docker.loc. IN A
;; ANSWER SECTION:
my-alpine.docker.loc. 3600 IN A 172.17.0.2
;; Query time: 0 msec
;; SERVER: 127.0.0.1#15353(127.0.0.1)
;; WHEN: Thu Apr 26 22:39:55 EDT 2018
;; MSG SIZE rcvd: 63
Stop the docker container will remove the corresponded DNS entries:
$ docker stop my-alpine
78c2a
$ dig @localhost -p 15353 my-alpine.docker.loc
;; QUESTION SECTION:
;my-alpine.docker.loc. IN A
Container will be resolved by label as nginx.loc
docker run --label=coredns.dockerdiscovery.host=nginx.loc nginx
See receipt how install for local development