How to communicate between Docker containers via “hostname”

Question

I plan to split my monolthic server up into many small docker containers but haven\'t found a good solution for \"inter-container communication\" yet. This is my target scen

Answer 1

Edit: After Docker 1.9, the docker network command (see below https://stackoverflow.com/a/35184695/977939) is the recommended way to achieve this.

---

My solution is to set up a dnsmasq on the host to have DNS record automatically updated: "A" records have the names of containers and point to the IP addresses of the containers automatically (every 10 sec). The automatic updating script is pasted here:

#!/bin/bash

# 10 seconds interval time by default
INTERVAL=${INTERVAL:-10}

# dnsmasq config directory
DNSMASQ_CONFIG=${DNSMASQ_CONFIG:-.}

# commands used in this script
DOCKER=${DOCKER:-docker}
SLEEP=${SLEEP:-sleep}
TAIL=${TAIL:-tail}

declare -A service_map

while true
do
    changed=false
    while read line
    do
        name=${line##* }
        ip=$(${DOCKER} inspect --format '{{.NetworkSettings.IPAddress}}' $name)
        if [ -z ${service_map[$name]} ] || [ ${service_map[$name]} != $ip ] # IP addr changed
        then
            service_map[$name]=$ip
            # write to file
            echo $name has a new IP Address $ip >&2
            echo "host-record=$name,$ip"  > "${DNSMASQ_CONFIG}/docker-$name"
            changed=true
        fi
    done < <(${DOCKER} ps | ${TAIL} -n +2)

    # a change of IP address occured, restart dnsmasq
    if [ $changed = true ]
    then
        systemctl restart dnsmasq
    fi

    ${SLEEP} $INTERVAL
done

Make sure your dnsmasq service is available on docker0. Then, start your container with --dns HOST_ADDRESS to use this mini dns service.

Reference: http://docs.blowb.org/setup-host/dnsmasq.html