Free and Open Source Load-Balancing Software and Projects

It's not Open Source, but it shares its spirit:
Why is it important to measure the internal maximum bandwidth of your machine ?
Which 10GbE NICs do we recommend ?
How can 10GbE load balancing performance be measured ?
How to build a 10GbE load balancer with BalanceNG

Apache: mod_athena

Full featured application load balancer for reverse proxy apache httpd mod_proxy.

Apache: mod_proxy_balancer

mod_proxy and related modules implement a proxy/gateway for Apache HTTP Server, supporting a number of popular protocols as well as several different load balancing algorithms. Third-party modules can add support for additional protocols and load balancing algorithms.


Balance is Inlab Network’s well known open source load balancing solution being a simple but powerful generic tcp proxy with round robin load balancing and failover mechanisms. Its behaviour can be controlled at runtime using a simple command line syntax.

Core Balance

Core Balance is a TCP Load Balancing proxy. It’s goal, unlike many load balancing proxies, is to balance based upon the node speed and available processing cores.


Looks like being discontinued.


Distributor is a software TCP load balancer. Like other load balancers, it accepts connections and distributes them to an array of back end servers. Distributor is compatible with any standard TCP protocol (HTTP, LDAP, IMAP, etc.) and is also IPv6 compatible. Distributor has many unique and advanced features and a high-performance architecture.

Eddie (written in Erlang)

Eddie is a high availability clustering tool. It is an open source, 100% software solution written primarily in the functional programming language Erlang ( and is available for Solaris, Linux and *BSD.

Enhydra Director

Director is a collection of open source web-server plugins to provide loadbalancing, clustering and unified connection methods for different web-servers on different platforms. The Enhydra Director supports several popular Web servers and operating systems, including Apache (on Linux/Unix and Windows), Netscape Enterprise Server (on Linux/UNIX and Windows), and Microsoft Internet Information Server (on Windows). Director also supports several applications servers: Tomcat (v5.xx and v5.5x), Jetty and Enhydra Application server.

GLB: GitHub’s open source load balancer

GLB Director is a Layer 4 load balancer which scales a single IP address across a large number of physical machines while attempting to minimise connection disruption during any change in servers. GLB Director does not replace services like haproxy and nginx, but rather is a layer in front of these services (or any TCP service) that allows them to scale across multiple physical machines without requiring each machine to have unique IP addresses.


HAProxy is a free, very fast and reliable 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. Over the years it has become the de-facto standard opensource load balancer, is now shipped with most mainstream Linux distributions, and is often deployed by default in cloud platforms. Since it does not advertise itself, we only know it’s used when the admins report it 🙂

Linux Network Load Balancing

Linux Network Load Balancing is an open-source project (kernel module + userland app.) aimed to realize decentered network load balancing clusters between Linux boxes.

Linux Virtual Server (LVS)

The Linux Virtual Server is a highly scalable and highly available server built on a cluster of real servers, with the load balancer running on the Linux operating system. The architecture of the server cluster is fully transparent to end users, and the users interact as if it were a single high-performance virtual server.

Load Balancer Project

Load Balancer Project is an attempt of write a tool that allows to balance request using clusters of servers. The goal is to archieve high availability, load balancing with a simple configuration for the load balancer, and the network topology.


Neutrino was build keeping the above requirements in mind. It is build in Scala language using Netty Server. It can do L7 routing using canonical names, url context and rule based. It has highly extensible pipeline architecture so that, new modules can be hooked into the pipeline without much work. Developers can add new switching rules and load balancing options easily. New modules can be added to send the log to API end point or load the configuration file from a DB or API. It is using JVM runtime environment, so developers can use either Java or Scala to add modules.


nginx [engine x] is an HTTP and reverse proxy server, a mail proxy server, and a generic TCP/UDP proxy server, originally written by Igor Sysoev. For a long time, it has been running on many heavily loaded Russian sites including Yandex, Mail.Ru, VK, and Rambler.

Octopus Load Balancer

Octopus Load Balancer is an extremely fast TCP load balancer with extensions for HTTP to allow balancing based on URI. Features include: server health checks and load polling, dynamic configuration, and the ability to carbon copy incoming requests.


OpenLoba was originally created for the VMware Ultimate Virtual Appliance Challenge , and was started  on March 10, 2006.
I have been messing around with different ideas and working on small little projects here and there and wanted to make some sort
of project available to the public and the VMware Challenge was the push that got me started. So basically OpenLoBa  is a bunch of open source tools put together to make a nice tcp load balancer solution with a web front end.


This is Pen, a highly scalable, highly available, robust load balancer for tcp and udp based protocols such as dns, http or smtp. It allows several servers to appear as one to the outside and automatically detects servers that are down and distributes clients among the available servers. This gives high availability and scalable performance.

Perlbal (implemented in Perl)

Perlbal is a Perl-based reverse proxy load balancer and web server.[2] Perlbal is maintained by a group connected to Danga Interactive. The program is in common use by large web sites to distribute the load over a number of servers.


The Pound program is a reverse proxy, load balancer and HTTPS front-end for Web server(s). Pound was developed to enable distributing the load among several Web-servers and to allow for a convenient SSL wrapper for those Web servers that do not offer it natively. Pound is distributed under the GPL – no warranty, it’s free to use, copy and give away.

Riverdrums Load Balancer

The Riverdrums Load Balancer is a feature-full, fast, event-driven frontend to enable high throughput access to clusters.


Varnish Cache is a web application accelerator also known as a caching HTTP reverse proxy. You install it in front of any server that speaks HTTP and configure it to cache the contents. Varnish Cache is really, really fast. It typically speeds up delivery with a factor of 300 – 1000x, depending on your architecture.

XLB HTTP Load Balancer

XLB is a high performance HTTP load balancer. connection management, caching, ssl, scripting. 300 mbit/sec / 4000 reqs/sec takes 30% cpu on a 2GhZ Xeon. connection pooling to backend servers reduces memory and cpu usage on backends.

Zevenet Load Balancer (former Zen Load Balancer)

Looks to be commercial now, we’ll check this.