nginxLoadBalancer

A small project to create a simple LoadBalancer, using Nginx to redirect to 4 other servers spun up using Docker. (for my own learning)

Technology & Learning

Nginx:

• using it as a proxy server

Docker:

• Building a Image (docker build)
• Spinning up the images (docker run)

Process/Guide

---

NGINX

for Mac users: brew install nginx

To Run:

nginx

see if it works, go to URL, and type localhost:8080. (will show up as "Welcome to nginx!")
Default nginx.conf file setting, port is opedn at 8080.

To Stop:

nginx -s stop

we can find the nginx folder using: nginx -t

Impt!! every time we want to make changes to the nginx need to run nginx -s reload

---

Dockerized Servers

To create a script

create a directory with mkdir and then cd into the directory

• first npm init
• then intall express : npm install express

create a simple index.js script:

const express = require("express");

const app = express();

app.get("/", (req, res) => {
  res.send("I am a endpoint");
});

app.listen(7777, () => {
  console.log("listening on port 7777");
});

if we run node index.js according to the script, then it will open the port at 7777, and we can reach the endpoint.

Using Docker to spin up Servers

create dockerfile

FROM node:18

# Create app directory, and set the working directory
WORKDIR /usr/src/app

# Install app dependencies
# A wildcard is used to ensure both package.json AND package-lock.json are copied
# where available (npm@5+)
# WE COPY the package.json
COPY package*.json ./

RUN npm install
# If you are building your code for production
# RUN npm ci --omit=dev

# Bundle app source
COPY . .

#EXPOSE 8080
EXPOSE 7777
# change to 7777, since the previous step, we initialize and open port at 7777


# this CMD means: ( to run > npm node index.js, inside the terminal in docker )
CMD ["node", "index.js"]

Building the docker IMAGE

run

docker build . -t myserver

(-t flag is to tag it with a name, in this case we name it "myserver")

docker run -p 1111:7777 -d myserver

docker run -p 2222:7777 -d myserver

docker run -p 3333:7777 -d myserver

docker run -p 4444:7777 -d myserver

to spin out 4 servers, which we map the different ports to the ports of the NGINX server to the opened ports in the docker container which is 7777

---

Now, to configure nginx.conf file again to make it into a LOAD BALANCER

edit the nginx.conf file and add the the upstream backendserver {} and also use the proxy_pass to make it rotate around the for servers.

http {
		include mime.types; # if we never use this, everything will be rendered as text/plain. so no CSS or others will be rendered

		# specify our backend, we can call it backendserver or any thing
		upstream backendserver {
				server 127.0.0.1:1111;
				server 127.0.0.1:2222;
				server 127.0.0.1:3333;
				server 127.0.0.1:4444;
		}

		server {
				listen 8080; # listening port
				root /Users/glow/Desktop/testNgnix; # the filePATH, that the bunch of file which we want to serve

				location / {
						#this proxy_pass will automatically do a roundrobin around all the listed server above.
						proxy_pass http://backendserver/;
				}
				location /fruits {
						root /Users/glow/Desktop/testNgnix;
						# if u search localhost:8080/fruits, it will go to this path: /Users/glow/Desktop/testNgnix/fruits ( the fruits folder, in the root PATH)
						# how it works is that, it will append "/fruits" to the end of the root path.
				}
				# location / means, everytime once it hit "/" directory immediately do the code below

				location /carbs {
						alias /Users/glow/Desktop/testNgnix/fruits;
						# alias will not append the location path to the end of the "alias" path. It will go Directly to the path
				}

		}
}

# don't need to use events{} , but we just need to define for nginx to work
events{}