30 Jun How To Set Up Nginx Load Balancing
Jun 30, 2015 – 6 min read
Introduction
Before we start with Nginx Load Balancing let’s review a few basic definitions (skip them if you are familiar).
NGINX
“Nginx (pronounced “engine x”) is a web server with a strong focus on high concurrency, performance and low memory usage. It can also act as a reverse proxy server for HTTP, HTTPS, SMTP, POP3, and IMAP protocols, as well as a load balancer and an HTTP cache.” – Wikipedia
Load balancing
Load balancing distributes workloads across multiple computing resources, such as computers, servers, central processing units, disk drivers, etc. Load balancing aims to optimize resource use, maximize throughput, minimize response time, and avoid overload of any single resource.
Load balancer
Load balancer is the server which distributes workloads across multiple computing resources also called back-end servers.
Back-end server
The back-end server is the server which takes the workload distributed by the load balancing server (load balancer).
In this tutorial we will:
- We will set up Nginx on two separate servers to work as back-end servers.
- On one of the two machines we will set up Nginx to work as a load balancing server.
In all of the examples in this tutorial, the following server to IP map will apply:
Server A: 1.1.1.1
Server B: 2.2.2.2
Also we will set up the servers to handle requests for the following domain name – example.com. All commands below are for Debian/Ubuntu Linux distribution and PHP 5.x.
Configure Nginx on Server A
The following steps will result in Server A and Server B sharing the load from the website traffic. The first thing we will do is to install Nginx.
The next thing is to set up Nginx to handle requests for example.com. Go to the following directory:
Open a new file which we will call “example”:
Place in the following configuration:
Save and close the file.
The role of the file “example” is that every time when we execute request to 1.1.1.1:8080 or example.com:8080, Nginx will return the content requested by us. This can be a static content like image, audio file, etc. The content can also be dynamic.
In order to understand the code above in details, read the comments inside the code.
Now we will set up the load balancer. Open the file “default”:
This is a default file which comes with the installation of Nginx. Clear tthe content which is already there and add the following configuration code:
The purpose of this code the following:
- The user types “example.com” in his/her web browser and hits Enter in order to send a request to the server where the website is physically located.
- The closest DNS server handles this request and with the help of the DNS map it knows that the request must be redirected to server with IP address 1.1.1.1 on port 80.
- The request is sent to 1.1.1.1 on port 80.
- The request is handled by Nginx (which is installed on the machine with IP 1.1.1.1) because Nginx listens for requests to domain name “example.com” on port 80.
- Nginx adds additional headers to the request (“Host” and “X-Forwarded-For”). They are required in order to inform the Back-end server for the host (the domain name) otherwise there is a danger the back-end server to be unable to handle the request.
- After that Nginx re-sends the request to one of the back-end servers listed in upstream. Please note that the name of the list is “backend” but you can choose any name. The request is re-send to port 8080!
Please note that Server A with IP 1.1.1.1 listens on two ports – 80 and 8080. The reason is simple. Port 80 is dedicated to the Load balancer and port 8080 is dedicated to the Back-end server (remember that Server A plays two roles in that particular case!). Server B, which we will configure shortly, will be only a back-end server and Nginx installed there will listen only on port 8080.
The next and final step is to enable those configurations. Go to:
and add a soft link for the newly created file “example”:
Once you’re done, reload Nginx:
Configure Nginx on Server B
We need to set up a similar virtual host block on Server B so it will also respond to requests for our domain. The first thing we will do is to install Nginx.
The next thing is to set up Nginx to handle requests for example.com. Open the following directory:
Open a new file which we will call “example”:
and place inside the following configuration:
As you may noticed, the configuration is exactly the same for the two back-end servers. The reason for that is because they both are listening on port 8080 in order to provide content requested for domain name example.com.
Go to:
and add a soft link for the newly created file “example”:
Once you’re done, reload Nginx:
That is the only configuration that we need on this server.
If everything else is set up, you can test the Nginx Load Balancing.
One of the drawbacks when dealing with load-balanced web servers is the possibility of data being out of sync between the servers. A solution to this problem might be employing a Git or SVN repository to sync to each server.
Take into account that Nginx allows you to choose the algorithm used to redirect the requests to the back-end server. There are also options to activate “Health Monitoring” and other features. For more details about this visit NGINX website.
If you need assistance with NGINX or setting up your Load Balancer, contact me.