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bpetschowitsch
173 lines
2.8 KiB
Markdown
173 lines
2.8 KiB
Markdown
# Load Balancer
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Simple guide to setup a load balancer based on nginx.
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## Backend Server
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First we need to create two backend-server:
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```bash
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cd /etc/nginx/sites-available
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sudo vi backend_server
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```
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```nginx
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server {
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listen 127.0.0.1:8080;
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server_name _;
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root /var/www/backend/srv1;
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index index.html;
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location / {
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try_files $uri $uri/ =404;
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}
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}
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server {
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listen 127.0.0.1:8081;
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server_name _;
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root /var/www/backend/srv2;
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index index.html;
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location / {
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try_files $uri $uri/ =404;
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}
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}
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```
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enable the new servers and validate configuration:
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```bash
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sudo ln -s /etc/nginx/sites-available/backend_server backend_server
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sudo nginx -t
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```
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restart nginx
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```bash
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sudo systemctl reload nginx
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```
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to verify the two servers are running:
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```bash
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sudo netstat -anp | grep -E "8080|8081"
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```
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## simple html
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the new webserver need an `index.html`
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```bash
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cd /var/www/
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sudo mkdir -p backend/srv1
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sudo mkdir -p backend/srv2
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```
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### srv1
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`index.html` of server one:
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```bash
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sudo vi backend/srv1/index.html
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```
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```html
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<html>
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<head>
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<title>Welcome!</title>
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</head>
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<body>
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<h1>Hello World! I am backend-server 1!</h1>
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</body>
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</html>
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```
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### srv2
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`index.html` of server two:
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```bash
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sudo vi backend/srv2/index.html
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```
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```html
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<html>
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<head>
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<title>Welcome!</title>
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</head>
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<body>
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<h1>Hello World! I am backend-server 2!</h1>
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</body>
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</html>
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```
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## Load Balancer
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lets create a new server as load balancer.
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```bash
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cd /etc/nginx/sites-available
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sudo vi loadbalancer
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```
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```nginx
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upstream my_backend_server {
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# default round-robin; other options: least_conn; ip_hash;
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# or using custom hash based on e.g. cookies: hash $cookie_<cookie-name> consistent;
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server 127.0.0.1:8080;
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server 127.0.0.1:8081;
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}
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server {
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listen 80;
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server_name *mydomain*;
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location / {
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proxy_pass http://my_backend_server;
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}
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}
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```
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enable the new configuration & verify:
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```bash
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sudo ln -f -s /etc/nginx/sites-available/loadbalancer *mydomain*
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sudo nginx -t
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```
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restart nginx:
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```bash
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sudo systemctl reload nginx
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```
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## Test
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load the website and refresh it serveral times...
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### simulate server crash
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simply change the listen port of one the backend-server (e.g. srv2 listen on 8082). Restart nginx. Retry the test.
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### simulate server failure
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before `location` add directive: `return 500;`. Restart nginx. Retry the test.
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## Handle server failure
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edit load balancer configuration:
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```nginx
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[...]
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location / {
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proxy_pass http://my_backend_server;
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proxy_next_upstream timeout http_500;
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}
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[...]
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```
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validate configuration, restart nginx and repeat the server failure test. |