Definition
A load balancer is a system (hardware or software) that distributes network or application traffic across multiple servers to optimize resource usage, minimize latency, and ensure system reliability.
By balancing the workload, the load balancer prevents the possibility of any single server from becoming a bottleneck and ensures no server is overwhelmed with excessive requests. This helps to maintain the performance and availability of services and applications.
Examples of Load Balancers
- Hardware load balancer: A physical device that is placed between the client and a server cluster, allocating traffic based on predefined rules and algorithms.
- Software load balancer: A load balancing system that is deployed on a virtual machine or container, providing greater flexibility and scalability than traditional hardware-based load balancers.
Load Balancer Algorithms
- Round Robin: Allocates incoming traffic requests across all the available servers evenly in a repeating patterns.
- Least connections: Sends incoming requests to the server with the lowest load.
- Internet Protocol (IP) Hash: Uses the hash function to allocate client IP addresses to specific servers.
Pros and Cons of Load Balancers
Pros
- Enhances service reliability and availability.
- Improves performance and reduces response time.
- Increases security through DDoS protection and SSL termination.
Cons
- Slightly expensive.
- Improper configuration can cause a single point of failure.
Load Balancer Best Practices
- Configure session persistence to ensure a consistent user experience by routing a user’s requests to the same server.
- Implement SSL termination to handle encryption/decryption tasks from backend servers.