https://github.com/myint/pen

Unofficial fork of the pen TCP/UDP load balancer (and reverse proxy) tool
https://github.com/myint/pen

Last synced: 4 days ago
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Unofficial fork of the pen TCP/UDP load balancer (and reverse proxy) tool

• Host: GitHub
• URL: https://github.com/myint/pen
• Owner: myint
• License: other
• Created: 2014-08-04T13:50:50.000Z (over 10 years ago)
• Default Branch: master
• Last Pushed: 2014-10-06T00:21:43.000Z (about 10 years ago)
• Last Synced: 2023-04-09T19:47:20.051Z (over 1 year ago)
• Language: C
• Homepage:
• Size: 371 KB
• Stars: 7
• Watchers: 3
• Forks: 6
• Open Issues: 0
• Metadata Files:
  • Readme: README.rst
  • Changelog: ChangeLog
  • License: COPYING

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README

        
pen

===

Unofficial fork of the pen TCP/UDP load balancer (and reverse proxy) tool.

.. image:: https://travis-ci.org/myint/pen.svg?branch=master

    :target: https://travis-ci.org/myint/pen

    :alt: Build status

Installation

============

::

    $ ./bootstrap

    $ ./configure

    $ make install

Usage

=====

Usage when forwarding a single port::

    $ pen -S 1 8888 savannah.nongnu.org:80

Description

===========

This is pen, a load balancer for "simple" TCP based protocols such as

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.

The load balancing algorithm keeps track of clients and will try to

send them back to the server they visited the last time. The client

table has a number of slots (default 2048, settable through command-line

arguments). When the table is full, the least recently used one will

be thrown out to make room for the new one.

This is superior to a simple round-robin algorithm, which sends a client

that connects repeatedly to different servers. Doing so breaks

applications that maintain state between connections in the server,

including most modern web applications.

When pen detects that a server is unavailable, it scans for another

starting with the server after the most recently used one. That way

we get load balancing and "fair" failover for free.

Correctly configured, pen can ensure that a server farm is always

available, even when individual servers are brought down for maintenance

or reconfiguration. The final single point of failure, pen itself,

can be eliminated by running pen on several servers, using VRRP to

decide which is active.

A side-effect of the load-balancing is that several logfiles are produced,

and all accesses seem to come from the load balancer. The program

penlogd solves this problem by merging pen's log file with the ones

produced by the web servers. See penlogd(1) and penlog(1) for details.

This load balancer is known to work on FreeBSD, Linux, HP-UX and Solaris.

Other Unixes should work as well, possibly requiring trivial changes.

Success stories or problem reports are welcome.

If pen is started with the -w option, statistics are saved in html

format when a USR1 signal is received.