An excellent blog post by jared robinson:

http://jaredrobinson.com/blog/whats-happening-with-version-control-systems/

One of my clients has come up with an http post erorr whilst trying to invoke a build.

Taking a look at the logs reveiled than indeed that the form post action instatiating the job didnt complete - this was very wiered,

The fact is all connection to server was within the clients LAN, with a fast enough connection between the client & server, which coulden't result in this type of error due to speed. (and yes on public instances you should expect the page to load 100% before you submit anything ...)

Whilst connected to the client LAN trying to reproduce the issue, I discovered two things

1. This was hapening on any form with in hudson - for exmeple hudson > manage hudson - which ruled out this is a specific plugin issue.

One of the pitfalls of Open Source with a big ecosystem like Hudson's (and many others) is you aren't always  up2date with the extentions / plugins out there.

Accoding to Kohsuke there are ~300 developoers world wide contributing to Hudson's extensibility, and points out the Selenium and Join plugins, see short interview embedded below:

As of now Hudson-CI is leading the poll, altough it seems like a "work in progress" for the list isn't 100% complete see: http://java.dzone.com/polls/which-continuous-integeration & see the posts comments.