Docker networking reverse proxy without docker-compose - networking

Question

The challenge
As described, I want to accomplish the same goal with docker itself as I would with the help of docker-compose.
I want to get a deeper understanding of docker and enable the ability to work with docker on platforms, where docker-compose is not an option.
What I do currently (with docker-compose)
1)
I use this docker-compose file:
---
version: '3'
services:
app:
build: .
proxy:
build: docker/proxy
ports:
- "80:80"
The "app" service starts a container which runs node on port 3002 (is exposed in the dockerfile)
The "proxy" service starts a container which runs an nginx with - among others - the following conf:
server {
listen 80;
server_name app;
location / {
proxy_pass http://app:3002;
}
}
2)
Then I add this to the /etc/hosts of my host pc:
127.0.0.1 app
3)
Now I run docker-compose up and vist http://app , which hits the node app.
Nice and simple, right?
Now I want to do the same only with docker.
What I've tried
1 using the same nginx configuration.
2 Starting the containers with a bash script
To accomplish this I
Created a network
Add the network to both containers
Setting up "app"-container hostname, network-alias and dns-search to "app" (because I hoped one of the options would help)
Here the script:
docker network create --driver bridge dockertest_nw
docker build -t dockertest_app .
docker create \
--name dockertest_app_con \
--network dockertest_nw \
--hostname app \
--network-alias=app \
--dns-search=app \
dockertest_app
docker build -t dockertest_proxy ./docker/proxy/
docker create \
--name dockertest_proxy_con \
--network dockertest_nw \
--hostname proxy \
--network-alias=proxy \
--dns-search=proxy \
-p 80:80 \
dockertest_proxy
docker start dockertest_proxy_con
docker start dockertest_app_con
Unfortunately, this doesn't work.
I also know there is a dns service from docker which docker-compose somehow uses and I should also use it on some way?
Could any one give some suggestions?
Update:
Just the info I got the following logs from the nginx container, which i would say shows the nginx doesn't can resolve "app" :
172.18.0.1 - - [13/Apr/2017:14:49:06 +0000] "GET / HTTP/1.1" 502 576 "-" "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/57.0.2987.133 Safari/537.36" "-"
2017/04/13 14:49:06 [error] 5#5: *13 connect() failed (111: Connection refused) while connecting to upstream, client: 172.18.0.1, server: app, request: "GET / HTTP/1.1", upstream: "http://127.0.0.1:3002/", host: "app"

Answer 1

You're tripping yourself up with all those options. All you really need is --network-alias to set the short form names app and proxy in your containers, which will be available in addition to the container names dockertest_app and dockertest_proxy.
docker network create --driver bridge dockertest_nw
docker build -t dockertest_app .
docker create \
--name dockertest_app \
--network dockertest_nw \
--network-alias=app \
dockertest_app
docker build -t dockertest_proxy ./docker/proxy/
docker create \
--name dockertest_proxy \
--network dockertest_nw \
--network-alias=proxy \
-p 80:80 \
dockertest_proxy
docker start dockertest_proxy
docker start dockertest_app