docker nginx ERR_NAME_NOT_RESOLVED - docker

Question

Running 4 docker containers: server/client/nginx/mongo reverse-proxy
The client seems to work on port 4200, I can see my app and routing works.
When trying to register a user, I am requesting the below httpclient post to the Docker container called "myserver" which should call the api.
I am getting this DNS error message.
When looking at the NGINX container at the resolv.conf (it shows 127.0.0.11) which is the correct dns Docker resolves the dns-es with within the container.
When I ping from within the container to another container's name it works.
when I telnet from within and outside of the container on the servers port 3000 it works as well as telnetting on client's port 4200
So what could be the cause of not being able to resolve myserver when I am trying to register an account on my website.
it is almost as if the call to register is being made from outside the container, so it can't resolve it, is this normal behavior?
let url = 'http://myserver:3000/api/register';
docker-compose.yml
version: '3'
services:
nginx:
build: ./nginx
# Map Nginx port 80 to the local machine's port 80
volumes:
- ./dist:/usr/share/nginx/html
ports:
- "80:80"
depends_on:
- client
networks:
- app-network
# Build the container using the client Dockerfile
client:
build: ./
# This line maps the contents of the client folder into the container.
volumes:
- ./:/usr/src/app
ports:
- "4200:4200"
networks:
- app-network
myserver:
build: ./express-server
volumes:
- ./express-server:/usr/src/server
environment:
- NODE_ENV=development
depends_on:
- mongo
ports:
- "3000:3000"
networks:
- app-network
# Link the client container so that Nginx will have access to it
mongo:
environment:
- AUTH=yes
- MONGO_INITDB_ROOT_USERNAME=superAdmin
- MONGO_INITDB_ROOT_PASSWORD=admin123
image: mongo
volumes:
- /var/mongodata/data:/data/db
ports:
- "27017:27017"
networks:
- app-network
networks:
app-network:
driver: bridge
nginx default.conf
worker_processes 2 ;
events {
worker_connections 1024;
}
http {
upstream my-server {
server myserver:3000;
}
upstream client {
server client:4200;
}
server {
location / {
proxy_pass http://client;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
proxy_set_header X-Forwarded-For $remote_addr;
}
location /api/ {
proxy_pass http://my-server;
proxy_http_version 1.1;
proxy_set_header Upgrade $http_upgrade;
proxy_set_header Connection 'upgrade';
proxy_set_header Host $host;
proxy_cache_bypass $http_upgrade;
proxy_set_header X-Forwarded-For $remote_addr;
}
}
}
cbdb2e00c6db meanchat_nginx "nginx -g 'daemon ..." 15 minutes ago Up 15 minutes 0.0.0.0:80->80/tcp meanchat_nginx_1
22406a1e9a31 meanchat_client "npm start" 15 minutes ago Up 15 minutes 0.0.0.0:4200->4200/tcp meanchat_client_1
aa024855d201 meanchat_myserver "npm start" About an hour ago Up 15 minutes 0.0.0.0:3000->3000/tcp meanchat_myserver_1
b657bd6db7b5 mongo "docker-entrypoint..." 5 hours ago Up 15 minutes 0.0.0.0:27017->27017/tcp b657bd6db7b5_meanchat_mongo_1
172.20.0.1 - - [09/Jan/2018:00:30:02 +0000] "GET /sockjs-node/info?t=1515457802565 HTTP/1.1" 200 90 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /register HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /sockjs-node/044/zh1t2skg/websocket HTTP/1.1" 101 162 "-" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /inline.bundle.js HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /polyfills.bundle.js HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /vendor.bundle.js HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /styles.bundle.js HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /scripts.bundle.js HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:03 +0000] "GET /main.bundle.js HTTP/1.1" 200 796563 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:06 +0000] "GET /assets/img/cryptoowls.jpg HTTP/1.1" 304 0 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:06 +0000] "GET /roboto-v15-latin-regular.7e367be02cd17a96d513.woff2 HTTP/1.1" 304 0 "http://localhost/" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:00:30:06 +0000] "GET /sockjs-node/info?t=1515457806564 HTTP/1.1" 200 90 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"
172.20.0.1 - - [09/Jan/2018:03:31:24 +0000] "GET /sockjs-node/info?t=1515468684563 HTTP/1.1" 200 90 "http://localhost/register" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/63.0.3239.132 Safari/537.36"

Answer 1

Answer from comments:
When connecting to containers with a reverse proxy, all the URL's used by the application need to point to that reverse proxy and not the application. Typically you do this by giving a path in the URL without a hostname. If you plan to use a virtual path based reverse proxy, you'll want to go a step further and use relative paths in your URL's. This all needs to happen in the responses being sent by the application to the client.