Is it Possible to Connect Docker Containers Through Http Using Http - docker

Question

I am attempting to use Docker to help deploy an application. The idea is to have two containers. One is the front-end containing Nginx and an Angular app.
FROM nginx
COPY ./dist/ /usr/share/nginx/html
COPY ./nginx.conf /etc/nginx/nginx.conf
It is supposed to contact a Spring Boot based API generated using the gradle-docker plugin and Dockerfile recommended by Spring:
FROM openjdk:8-jdk-alpine
VOLUME /tmp
ARG JAR_FILE
COPY ${JAR_FILE} app.jar
ENTRYPOINT ["java","-Djava.security.egd=file:/dev/./urandom","-jar","/app.jar"]
They seem to run fine individually (I can access them on my development machine); however, I am having trouble connecting the two.
My docker-compose.yml file:
version: '3'
services:
webapp:
image: com.midamcorp/emp_front:latest
ports:
- 80:80
- 443:443
networks:
- app
api:
image: com.midamcorp/employee_search:latest
ports:
- 8080:8080
networks:
- app
networks:
app:
Based upon my understanding of the Docker documentation on networks, I was under the impression that the containers would be placed in the same network and thus could interact, with the service name (for example, api) acting as the "host". Based upon this assumption, I am attempting to access the API from the Angular application through the following:
private ENDPOINT_BASE: string = "http://api:8080/employee";
This returns an error: Http failure response for (unknown url): 0 Unknown Error.
To be honest, the sample I have looked at used this concept (substituting the service name for host to connect two containers) for database applications not HTTP. Is what I am attempting to accomplish not possible?
EDIT:
My nginx.conf
worker_processes 1;
events {
worker_connections 1024;
}
http {
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
server {
listen 80;
server_name localhost;
root /usr/share/nginx/html;
location / {
index index.html index.htm;
try_files $uri $uri/ /index.html;
}
}
}
EDIT:
Updated nginx.conf
worker_processes 1;
events {
worker_connections 1024;
}
http {
upstream docker-java {
server api:8080;
}
include mime.types;
default_type application/octet-stream;
sendfile on;
keepalive_timeout 65;
server {
listen 8081;
server_name localhost;
location / {
proxy_pass http://docker-java;
proxy_redirect off;
proxy_set_header Host $host;
proxy_set_header X-Real-IP $remote_addr;
proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
proxy_set_header X-Forwarded-Host $server_name;
}
}
server {
listen 80;
server_name localhost;
root /usr/share/nginx/html;
location / {
index index.html index.htm;
try_files $uri $uri/ /index.html;
}
}
}
and docker-compose.yml
version: '3'
services:
webapp:
image: com.midamcorp/emp_front:latest
ports:
- 80:80
- 443:443
networks:
- app
depends_on:
- api
api:
image: com.midamcorp/employee_search:latest
networks:
- app
networks:
app:
And the client / Angular app uses the following to contact the API private ENDPOINT_BASE: string = "http://localhost:8081/employee";
Output from docker ps
> docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
947eb757eb4b b28217437313 "nginx -g 'daemon of…" 10 minutes ago Up 10 minutes 0.0.0.0:80->80/tcp, 0.0.0.0:443->443/tcp employee_service_webapp_1
e16904db67f3 com.midamcorp/employee_search:latest "java -Djava.securit…" 10 minutes ago Up 10 minutes employee_service_api_1

Answer 1

The problem you are experiencing is not anything weird. It's just that you did not explicitly name your containers. Instead, Docker generated a the names by itself. So, nginx will resolve employee_service_api_1, but will not recognize just api. Open you webapp container and take a look at your hosts (cat /etc/hosts) - it will show you employee_service_api_1 and it's IP address.
How to fix it.
Add container_name to your docker-compose.yml:
version: '3'
services:
webapp:
image: com.midamcorp/emp_front:latest
container_name: employee_webapp
ports:
- 80:80
- 443:443
networks:
- app
depends_on:
- api
api:
image: com.midamcorp/employee_search:latest
container_name: employee_api
networks:
- app
networks:
app:
I always refrain from using "simple" names (i.e. just api), cuz on my system multiple containers with similar names might show up, so I add some prefix. In this case I named the api container employee_api and now nginx will resolve to that name once you restart your containers.