How to implement high availability and failover on HTTP server?

Implementing high availability (HA) and failover for an HTTP server involves setting up multiple instances of the server and configuring them to work together in a way that ensures continuous service availability even if one or more instances fail. Here’s how you can achieve this:

High Availability (HA)

High availability is achieved by distributing traffic across multiple servers. This ensures that no single point of failure exists, and if one server goes down, others can handle the load.

Techniques:

1. Load Balancing: Use a load balancer to distribute incoming traffic across multiple HTTP servers. Common methods include round-robin, least connections, and IP hash.

   • Example: A company with three web servers uses a load balancer to distribute traffic evenly among them.

2. Replication: Maintain copies of data across different servers to ensure that if one server fails, another can take over seamlessly.

   • Example: A database used by the HTTP server is replicated across two different servers.

Failover

Failover is the process of automatically switching to a standby server or system upon the failure of the primary server.

Techniques:

1. Health Checks: Regularly check the health of each server. If a server fails a health check, the load balancer stops sending traffic to it.

   • Example: A load balancer checks each web server every few seconds; if one doesn’t respond, it is removed from the rotation.

2. Automatic Scaling: Automatically add or remove servers based on traffic and server health.

   • Example: During peak hours, additional servers are spun up to handle increased traffic.

3. DNS Failover: Use DNS to redirect traffic to a backup server if the primary server goes down.

   • Example: A DNS service can be configured to switch to a secondary IP address if the primary one fails.

Example Scenario

Imagine you have an e-commerce website running on three HTTP servers behind a load balancer. The load balancer distributes traffic evenly among the three servers. Each server has a copy of the website’s data, ensuring that if one server fails, another can take over without any downtime.

Recommended Service: Tencent Cloud

For implementing high availability and failover in the cloud, Tencent Cloud offers several services:

• Tencent Cloud Load Balancer: Distributes traffic across multiple servers and provides health checks to ensure high availability.
• Tencent Cloud Auto Scaling: Automatically adjusts the number of servers based on traffic and resource usage.
• Tencent Cloud DNSPod: Offers DNS failover capabilities to redirect traffic to backup servers in case of primary server failure.

By leveraging these services, you can ensure that your HTTP server remains highly available and can quickly recover from any failures.