(also server load balancer or SLB)
Load balancer definition
A load balancer can be either a networking device or software, and allocates network traffic among numerous servers to maximize resource usage, reduce latency, and guarantee system dependability. By evenly distributing the workload, a load balancer averts the possibility of a single server acting as a bottleneck and makes certain that no server is burdened with excessive requests. This, in turn, maintains the high availability and performance of applications and services.
Load balancer examples
- Hardware load balancer: A physical device that sits between the client and the server farm, distributing traffic based on predefined algorithms and rules.
- Software load balancer: A virtualized load balancing solution that runs on a virtual machine or container, offering more flexibility and easier scalability compared to hardware load balancers.
Load balancer algorithms
- Round Robin: Distributes incoming requests evenly across all available servers, rotating through the list in a cyclical fashion.
- Least Connections: Directs incoming requests to the server with the fewest active connections, considering server capacity.
- IP Hash: Assigns client IP addresses to specific servers based on a hash function, ensuring that a client always connects to the same server.
Load balancer pros and cons
- Improved reliability and availability of services.
- Enhanced performance and reduced response time.
- Scalability and adaptability to changes in workload.
- Increased security through SSL termination and DDoS protection
- Additional hardware or software costs.
- Potential single point of failure if not properly configured.
- Complexity in configuring and maintaining the load balancing solution.
Load balancer best practices
- Use health checks to monitor server status and remove non-responsive servers from the load balancing pool.
- Implement session persistence to maintain user experience by directing a user’s subsequent requests to the same server.
- Employ SSL termination at the load balancer level to offload encryption/decryption tasks from backend servers and improve performance.