docker容器网络无法按预期工作

Question

I created two docker images and started them using docker compose.

docker-compose.yaml

version: '2'
services:
  dmgr:
    hostname: dmgr
    image: dmgr
    build:
      context: ./dmgr
    ports:
     - "9060:9060"
    tty: true

  custom1:
    hostname: node
    image: node
    build:
      context: ./custom
    ports:
     - "9080:9080"
    environment:
     - PROFILE_NAME=Node
     - HOST_NAME=node
     - NODE_NAME=Node
     - DMGR_HOST=dmgr
     - DMGR_PORT=8879
    depends_on:
     - dmgr

after the two containers start, second container "node" is able to resolve and ping container "dmgr" but other way is not working

root@node:/# nslookup dmgr
Server:    127.0.0.11
Address:    127.0.0.11#53
Non-authoritative answer:
Name:   dmgr
Address: 172.18.0.2

root@node:/# cat /etc/hosts
127.0.0.1   localhost
::1 localhost ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
172.18.0.3  node

root@node:/# cat /etc/resolv.conf 
nameserver 127.0.0.11
options ndots:0

If I exec to container "dmgr" and run "nslookup node", its not able to resolve. what am I doing wrong? please someone point me in correct direction

root@dmgr:/# nslookup node
Server:     127.0.0.11
Address:    127.0.0.11#53

** server can't find node: NXDOMAIN

Answer 1

Hostname will not resolve with docker's embedded DNS (counterintuitive, but this can be changed outside of the control of docker, so there's some logic). What will resolve is the container name and the service name, custom1. Changing the service name would solve your issue:

version: '2'
services:
  dmgr:
    hostname: dmgr
    image: dmgr
    build:
      context: ./dmgr
    ports:
     - "9060:9060"
    tty: true

  node:
    image: node
    build:
      context: ./custom
    ports:
     - "9080:9080"
    environment:
     - PROFILE_NAME=Node
     - HOST_NAME=node
     - NODE_NAME=Node
     - DMGR_HOST=dmgr
     - DMGR_PORT=8879
    depends_on:
     - dmgr

You can also define a network alias if you need to resolve something different:

version: '2'
services:
  dmgr:
    hostname: dmgr
    image: dmgr
    build:
      context: ./dmgr
    ports:
     - "9060:9060"
    tty: true

  custom1:
    image: node
    build:
      context: ./custom
    ports:
     - "9080:9080"
    networks:
      default:
        aliases:
         - node
    environment:
     - PROFILE_NAME=Node
     - HOST_NAME=node
     - NODE_NAME=Node
     - DMGR_HOST=dmgr
     - DMGR_PORT=8879
    depends_on:
     - dmgr

https://docs.docker.com/compose/compose-file/#aliases