HAProxy is a free, very fast and reliable open source solution offering high availability, load balancing, and proxying for TCP and HTTP-based applications. It is particularly suited for very high-traffic web sites and powers quite a number of the world's most visited ones. HAProxy stats monitoring is available with the Telegraf plugin integration.
Telegraf Input Plugin: HAProxy
Easily track key web server performance metrics from any running HAProxy monitoring instance. You can gather key front end metrics (https requests per second, # of HTTP client of server errors, etc) as well as backend metrics (average response time, # of requests that produced an error) to ensure proper performance and operation.
HAProxy is known as the reliable, high performance TCP/HTTP Load Balancer. Having become, over the years, the de-facto standard opensource load balancer, it is now shipped with most mainstream Linux distributions and often deployed by default in cloud platforms.
HAProxy involves several techniques commonly found in Operating Systems architectures to achieve the absolute maximal performance.
HAProxy has been installed on Linux 2.4 systems serving millions of pages every day.
Vulnerabilities are very rarely encountered on HAProxy, and its architecture significantly limits their impact and often allows easy workarounds.