Mysql connect host change every time in the docker container,why? - mysql

Question

In the docker container.I try to login the host mysql server. First the host ip is changed,so confused for me.But second login success. Anyone can explain this strange happening?
I login ip is 192.168.100.164,but the error info shows ip 172.18.0.4,which is the container localhost.
More info:
root#b67c39311dbb:~/project# netstat -nr
Kernel IP routing table
Destination Gateway Genmask Flags MSS Window irtt Iface
0.0.0.0 172.18.0.1 0.0.0.0 UG 0 0 0 eth0
172.18.0.0 0.0.0.0 255.255.0.0 U 0 0 0 eth0
root#b67c39311dbb:~/project# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 172.18.0.4 netmask 255.255.0.0 broadcast 172.18.255.255
ether 02:42:ac:12:00:04 txqueuelen 0 (Ethernet)
RX packets 2099 bytes 2414555 (2.4 MB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1752 bytes 132863 (132.8 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
inet 127.0.0.1 netmask 255.0.0.0
loop txqueuelen 1000 (Local Loopback)
RX packets 35 bytes 3216 (3.2 KB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 35 bytes 3216 (3.2 KB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

Answer 1

Try adding --add-host="localhost:192.168.100.164" when launching docker run. But this is not a good practice to my mind. You should move your mysql database to another container and create a network between them

Answer 2

That is true, when we start docker container it is get their own ip for container. You need to map host port with docker container. then, when you try to connect host port it redirect to myssql docker container. Please look at https://docs.docker.com/config/containers/container-networking/

Answer 3

I'd suggest you to create a docker bridged network and then create your container using the --add-host as suggested by Alexey.
In a simple script:
DOCKER_NET_NAME='the_docker_network_name'
DOCKER_GATEWAY='172.100.0.1'
docker network create \
--driver bridge \
--subnet=172.100.0.0/16 \
--gateway=$DOCKER_GATEWAY \
$DOCKER_NET_NAME
docker run -d \
--add-host db.onthehost:$DOCKER_GATEWAY \
--restart=always \
--network=$DOCKER_NET_NAME \
--name=magicContainerName \
yourImage:latest
EDIT: creating a network will also simplify the communication among containers (if you plan to have it in the future) since you'll be able to use the container names instead of their IP.