In load balancing, what is the purpose of a health check?

In load balancing, what is the purpose of a health check?

• A. A mechanism to verify DNS records are current.
• B. A technique to balance load using DNS round-robin.
• C. A mechanism to verify backend servers are healthy before sending traffic; ensures high availability.
• D. A tool to monitor bandwidth usage.

Answer: (C)

Health checks are active probes a load balancer uses to confirm that each backend server can handle requests. By periodically sending test requests (like HTTP, TCP, or ICMP probes) and evaluating the responses, the balancer determines whether a server is healthy. If a server responds correctly, it stays in the pool; if it fails or times out, the balancer marks it unhealthy and stops sending new traffic there, directing clients to healthy servers instead. This helps prevent users from hitting a downed or slow node and supports high availability and fast recovery when a server comes back online. It's not about verifying DNS records or using DNS round-robin for distribution, and it's not primarily about monitoring bandwidth usage—the focus is service readiness and responsiveness.

Health checks are active probes a load balancer uses to confirm that each backend server can handle requests. By periodically sending test requests (like HTTP, TCP, or ICMP probes) and evaluating the responses, the balancer determines whether a server is healthy. If a server responds correctly, it stays in the pool; if it fails or times out, the balancer marks it unhealthy and stops sending new traffic there, directing clients to healthy servers instead. This helps prevent users from hitting a downed or slow node and supports high availability and fast recovery when a server comes back online. It's not about verifying DNS records or using DNS round-robin for distribution, and it's not primarily about monitoring bandwidth usage—the focus is service readiness and responsiveness.