HAProxy and Keepalived for Highly Performance Load-Balancing on Ubuntu
This article explains how to set up a two-node based load balancers in an active/passive fashion, using HAProxy and keepalived on Ubuntu Server.
HAproxy is a high-performance and highly-robust HTTP and TCP load-balancer which provides cookie-based persistence, auto failover, header modification on the fly, weighted load balancing, advanced logging and many more more features. It can easily handle up to ten thousands hits per second on modern hardware(s), and even with thousands of simultaneous connections. Unlike other free load-balancing solutions, this product is used by a few hundreds of people around the world - but those people run very big sites serving several millions hits. But it's a too good piece of s/w - which getting popular very fast.
keepalived is to add a strong & robust keepalive facility to the HAProxy load-balancers (also known as directors). This is written in C with multilayer TCP/IP stack checks (Layer3, Layer4 & Layer5/7). Here in examples, Keepalived implements an independent VRRPv2 stack to handle HAproxy directors failover.
DjbDNS Setup On Ubuntu Server (amd64)
DjbDNS is a collection of Domain Name System tools. It includes software for all the fundamentals of DNS operations:
1. DNS Cache: Used for finding addresses of Internet hosts. When a browser wants to contact any domain-name, it first asks to a DNS Cache, such as DjbDNS's dnscache, to find the IP address of that domain-name. Internet service providers run dnscache to find IP addresses requested by their customers. If you're running a home computer or a workstation, you can also run your own dnscache to speed up your web browsing.
2. DNS Server: Used for publishing addresses of Internet hosts. The IP address of any domain is published by some DNS servers (DNS server of Hosting Party). djbdns includes a general-purpose DNS server, named tinydns. Network/System administrators run tinydns to publish the IP addresses of their Internet hosts. DjbDNS also includes special-purpose servers for publishing DNS walls and RBLs.
3. DNS Client: These are client applications which talks to a DNS cache. DjbDNS includes DNS client C libraries and several command-line DNS client utilities. Programmers use these tools to send requests to DNS cache.