Docker + nginx + angular +弹簧靴

Question

I am trying a simple angular app with a spring boot backend using docker compose. But my front end cant seem to find the backend api when called. Below are the relevant files.

Docker File for Backend

#
# Build
#
FROM maven:3.6.0-jdk-11-slim AS build
COPY src /home/app/src
COPY pom.xml /home/app
RUN mvn -f /home/app/pom.xml clean package

#
# Package stage
#
FROM openjdk:11-jre-slim
COPY --from=build /home/app/target/demo-0.0.1-SNAPSHOT.jar /usr/local/lib/demo.jar
EXPOSE 8080
ENTRYPOINT ["java","-jar","/usr/local/lib/demo.jar"]

Docker File for frontend angular

FROM node:alpine AS builder

WORKDIR /app

COPY . .

RUN npm install && \
    npm run build

FROM nginx:alpine

COPY --from=builder /app/dist/* /usr/share/nginx/html/
COPY /nginx.conf /etc/nginx/conf.d/default.conf

NGINX conf file used

server {
    include /etc/nginx/extra-conf.d/*.conf;
    
    listen 80;
    server_name frontend;
    
    location / {
        root /usr/share/nginx/html;
        index index.html index.htm;
        try_files $uri $uri/ /index.html =404;
    }
    
    location /api/ { 
        proxy_http_version 1.1;
        #proxy_pass http://<ContainerName>:<PortNumber>; 
        # In our case Container name is as we setup in docker-compose `beservice` and port 8080
        proxy_pass http://backend:8080/api/;   
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection 'upgrade';
        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-NginX-Proxy true;
        proxy_cache_bypass $http_upgrade;
    } 
}

Docker Compose Yml

version: "3.9"

services:
    backend:
        image: demo
        container_name: demo
        build:
            context: ./demo
        ports:
            - 8080:8080
    frontend:
        image: demo-ui
        container_name: demo-ui
        build:
            context: ./my-demo-ui
        ports:
            - 80:80
        depends_on:
            - backend
        links: 
            - backend

The Front end application comes up but when I hit the backend app (through angular/nginx) it gives a 502 Bad Gateway Error.

Also I see these printed in NGINX console in docker

 [error] 30#30: *1 connect() failed (110: Operation timed out) while connecting to upstream, client: 172.18.0.1, server: , request: "GET /api/demoMethod HTTP/1.1", upstream: "http://172.17.0.2:8080/api/demoMethod", host: "localhost", referrer: "http://localhost/home"

Answer 1

In your docker-compose file you have

container_name: demo

but in the nginx configuration you're using the name backend . You have to use the container name demo in the nginx configuration. The service name backend can only be used inside the docker-compose file.

Additionally:

Warning

The --link flag is a legacy feature of Docker. It may eventually be removed. Unless you absolutely need to continue using it, we recommend that you use user-defined networks to facilitate communication between two containers instead of using --link.

One feature that user-defined networks do not support that you can do with --link is sharing environmental variables between containers. However, you can use other mechanisms such as volumes to share environment variables between containers in a more controlled way.

Docker Composer doc

Answer 2

Here you're missing the network configuration in the Docker-compose file, you need to link your two container so they can see one another.