I have the Docker version 1.10 with embedded DNS service.
I have created two service containers in my docker-compose file. They are reachable each other by hostname and by IP, but when I would like reach one of them from the host machine, it doesn't work, it works only with IP but not with hostname.
So, is it possible to access a docker container from the host machine by it's hostname in the Docker 1.10, please?
Update:
docker-compose.yml
version: '2'
services:
service_a:
image: nginx
container_name: docker_a
ports:
- 8080:80
service_b:
image: nginx
container_name: docker_b
ports:
- 8081:80
then I start it by command: docker-compose up --force-recreate
when I run:
docker exec -i -t docker_a ping -c4 docker_b
- it worksdocker exec -i -t docker_b ping -c4 docker_a
- it worksping 172.19.0.2
- it works (172.19.0.2
is docker_b
's ip)ping docker_a
- failsThe result of the docker network inspect test_default
is
[
{
"Name": "test_default",
"Id": "f6436ef4a2cd4c09ffdee82b0d0b47f96dd5aee3e1bde068376dd26f81e79712",
"Scope": "local",
"Driver": "bridge",
"IPAM": {
"Driver": "default",
"Options": null,
"Config": [
{
"Subnet": "172.19.0.0/16",
"Gateway": "172.19.0.1/16"
}
]
},
"Containers": {
"a9f13f023761123115fcb2b454d3fd21666b8e1e0637f134026c44a7a84f1b0b": {
"Name": "docker_a",
"EndpointID": "a5c8e08feda96d0de8f7c6203f2707dd3f9f6c3a64666126055b16a3908fafed",
"MacAddress": "02:42:ac:13:00:03",
"IPv4Address": "172.19.0.3/16",
"IPv6Address": ""
},
"c6532af99f691659b452c1cbf1693731a75cdfab9ea50428d9c99dd09c3e9a40": {
"Name": "docker_b",
"EndpointID": "28a1877a0fdbaeb8d33a290e5a5768edc737d069d23ef9bbcc1d64cfe5fbe312",
"MacAddress": "02:42:ac:13:00:02",
"IPv4Address": "172.19.0.2/16",
"IPv6Address": ""
}
},
"Options": {}
}
]
Here's what I do.
I wrote a Python script called dnsthing, which listens to the Docker events API for containers starting or stopping. It maintains a hosts
-style file with the names and addresses of containers. Containers are named <container_name>.<network>.docker
, so for example if I run this:
docker run --rm --name mysql -e MYSQL_ROOT_PASSWORD=secret mysql
I get this:
172.17.0.2 mysql.bridge.docker
I then run a dnsmasq
process pointing at this hosts
file. Specifically, I run a dnsmasq instance using the following configuration:
listen-address=172.31.255.253
bind-interfaces
addn-hosts=/run/dnsmasq/docker.hosts
local=/docker/
no-hosts
no-resolv
And I run the dnsthing
script like this:
dnsthing -c "systemctl restart dnsmasq_docker" \
-H /run/dnsmasq/docker.hosts --verbose
So:
dnsthing
updates /run/dnsmasq/docker.hosts
as containers
stop/startdnsthing
runs systemctl restart dnsmasq_docker
dnsmasq_docker
runs dnsmasq
using the above configuration, bound
to a local bridge interface with the address 172.31.255.253
.The "main" dnsmasq process on my system, maintained by
NetworkManager, uses this configuration from
/etc/NetworkManager/dnsmasq.d/dockerdns
:
server=/docker/172.31.255.253
That tells dnsmasq to pass all requests for hosts in the .docker
domain to the docker_dnsmasq
service.
This obviously requires a bit of setup to put everything together, but after that it seems to Just Work:
$ ping -c1 mysql.bridge.docker
PING mysql.bridge.docker (172.17.0.2) 56(84) bytes of data.
64 bytes from 172.17.0.2: icmp_seq=1 ttl=64 time=0.087 ms
--- mysql.bridge.docker ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.087/0.087/0.087/0.000 ms