Starting NGINX Load Balancer with Docker Compose - nginx

Question

I have been following a tutorial on how to make a load balanced application using docker-compose and nginx. However, my load balancer/coordinator doesn't work - what I am trying to do is have nginx accept requests and split them between three workers, and I want nginx and the three workers to be running in separate docker containers, but I get the following error. My compilerwebservice_worker does work correctly, and I can see all three in docker ps, and I can ping them with wget on the localhost post they are listening to.
The error message
$ docker-compose up
Starting compilerwebservice_worker1_1
Starting compilerwebservice_worker3_1
Starting compilerwebservice_worker2_1
Starting compilerwebservice_nginx_1
Attaching to compilerwebservice_worker1_1, compilerwebservice_worker3_1, compilerwebservice_worker2_1, compilerwebservice_nginx_1
nginx_1 | 2016/09/06 07:17:47 [emerg] 1#1: host not found in upstream "compiler-web-service" in /etc/nginx/nginx.conf:14
nginx_1 | nginx: [emerg] host not found in upstream "compiler-web-service" in /etc/nginx/nginx.conf:14
compilerwebservice_nginx_1 exited with code 1
NGINX Config
http {
upstream compiler {
least_conn;
server worker1:4567;
server worker2:4567;
server worker3:4567;
}
server {
listen 4567;
location / {
proxy_pass http://compiler;
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;
}
}
}
My Docker-compose file
nginx:
build: ./src/main/nginx
links:
- worker2:worker2
- worker3:worker3
- worker1:worker1
ports:
- "4567:4567"
worker1:
build: .
ports:
- "4567"
worker2:
build: .
ports:
- "4567"
worker3:
build: .
ports:
- "4567"
NGINX Docker file
# Set nginx base image
FROM nginx
# Copy custom configuration file from the current directory
COPY nginx.conf /etc/nginx/nginx.conf

Answer 1

In the below demo there are 2 express app running with port 1111 and 2222 in localhost, on calling http://localhost:8080 it should automatically choose any one of the port 1111 or 2222. here nginx uses round robin
index.js file
const express = require('express');
const app = express();
const appId = process.env.APPID;
const PORTNUMBER = appId;
app.get('/', (req, res) => {
res.send({
message: `Welcome to ${appId} home page running on port ${appId}`
});
});
app.listen(PORTNUMBER, () => {
console.log(`APP STARTED ON PORT ${appId} for APP id ${appId}`);
})
express app docker file
FROM node:12.13.0-alpine
WORKDIR /EXPRESSAPP
COPY ./API/package.json /EXPRESSAPP
RUN npm install
COPY ./API/. /EXPRESSAPP
CMD ["npm", "start"]
nginx file
http {
upstream backend {
server 127.0.0.1:1111;
server 127.0.0.1:2222;
}
server {
listen 8080 default_server;
listen [::]:8080 default_server;
# listen [::]:8080 default_server ipv6only=on;
server_name localhost;
proxy_read_timeout 5m;
location / {
proxy_http_version 1.1;
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-Forwarded-Proto $scheme;
proxy_cache_bypass $http_upgrade;
proxy_pass http://backend;
}
}
}
nginx dockercompose file
FROM nginx
COPY nginx.conf /etc/nginx/nginx.conf
docker-compose.yml file
version: '3'
services:
myapp1:
restart: always
container_name: myapp1
build: ./APICONTAINER
environment:
- APPID=1111
ports:
- "1111:1111"
network_mode: host
myapp2:
restart: always
container_name: myapp2
build: ./APICONTAINER
environment:
- APPID=2222
ports:
- "2222:2222"
network_mode: host
myproxy:
container_name: myproxy
build: ./NGINXCONTAINER
ports:
- "127.0.0.1:8080:8080"
depends_on:
- myapp1
- myapp2
network_mode: host
to spin up the containers use the below command
sudo docker-compose down && sudo docker-compose up --build --force-recreate
go to below link to see the round robin nginx load balancer
http://localhost:8080
reference github link to get the full code

Answer 2

I needed to rebuild with docker-compose build between configuration changes. As I changed the name of the app, the error message indicated a server, whose name was the original one that I selected instead of the one I kept changing.