What is HAProxy?
HAProxy (High Availability Proxy) is a TCP/HTTP load balancer and proxy server that allows a webserver to spread incoming requests across multiple endpoints. This is useful in cases where too many concurrent connections over-saturate the capability of a single server. Instead of a client connecting to a single server which processes all the requests, the client will connect to an HAProxy instance, which will use a reverse proxy to forward the request to one of the available endpoints, based on a load-balancing algorithm.
Types of Load Balancing
Now that we understand the basic components that are used in load balancing, let’s get into the basic types of load balancing.
No Load Balancing
A simple web application environment with no load balancing might look like the following:
In this example, the user connects directly to your web server, at xyz.com and there is no load balancing. If your single web server goes down, the user will no longer be able to access your web server. Additionally, if many users are trying to access your server simultaneously and it is unable to handle the load, they may have a slow experience or they may not be able to connect at all.
Layer 4 Load Balancing
The simplest way to load balance network traffic to multiple servers is to use layer 4 (transport layer) load balancing. Load balancing this way will forward user traffic based on IP range and port (i.e. if a request comes in for http://xyz.com/anything, the traffic will be forwarded to the backend that handles all the requests for xyz.com on port 80).
Here is a diagram of a simple example of layer 4 load balancing:
The user accesses the load balancer, which forwards the user’s request to the web-backendgroup of backend servers. Whichever backend server is selected will respond directly to the user’s request. Generally, all the servers in the web-backend should be serving identical content–otherwise the user might receive inconsistent content. Note that both web servers connect to the same database server.
Continue on https://foxutech.com/what-is-haproxy-and-how-to-install-and-configure-in-linux/
