LOAD BALANCING

What Is Load Balancing?

Load balancing is a component of highly-available infrastructures commonly used to improve the performance and reliability of web sites, applications, databases and other services by distributing the workload across multiple servers. Load balancers are used to increase capacity and consistency of applications. They improve the overall performance of applications by decreasing the burden on servers associated with managing and maintaining application and network sessions, as well as by performing application-specific tasks.

How does Load Balancer work?

To distribute the necessary tasks, load balancers go through a series of steps. First, the load balancer will query the available servers to ensure their availability. The load balancer rings a server, and if the expected response occurs, it will be included in the available list. If the server fails to respond, it will not be used until another test is performed and it returns with the appropriate response. Load balancing software is very flexible in this environment, as the administrator can quickly turn the system to ensure it is checking servers appropriately and accurately.

Distributing the load between the active servers can be done in several different ways. The load balancer may use a round-robin method, where each server is used in turn. It can also use a weighted round robin system, where servers are assigned traffic based on their configured capabilities.

Load balancing methods will vary greatly between different networks and organizations depending on the needs of the organization and the equipment available to perform the task. Load Balancers can handle Traffics like HTTP, HTTPS, TCP, UDP

The load balancer chooses the backend server with the combination of two factors:

- Health Checks - Load Balancing Algorithms

Benefits of Load Balancer:

? Increased Scalability

? Redundancy

? Reduced Downtime, Increased Performance

? Efficiently Manages Failures

? Increased Flexibility

Testing Point of view:

“Performance Testing” is going to be the best indicator of whether the load balancer is configured in the best possible way for site. In fact, the only other way to see if the load balancer is configured properly is to release it into production and monitor the traffic. 

To exercise the load balancer in a way that’s useful for determining if it’s configured properly, we will need to make virtual testers appear to be coming from unique IP addresses (since most load balancers identify users by IP address). If the load balancer doesn’t recognize virtual users as being unique users, it’s not likely to balance the load properly. There are only two ways to make virtual testers appear to be coming from unique IP addresses use a lot of agents or enable IP aliasing through Test Manager.