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. A high level overview of what Varnish does can be seen in the video attached to this web page.
Varnish Cache Performance
Varnish performs really, really well. It is usually bound by the speed of the network, effectivly turning performance into a non-issue. We've seen Varnish delivering 20 Gbps on regular off-the-shelf hardware.
Varnish Server Flexibility
One of the key features of Varnish Cache, in addition to it's performance, is the flexibility of it's configuration language, VCL. VCL enables you to write policies on how incoming requests should be handled. In such a policy you can decide what content you want to serve, from where you want to get the content and how the request or response should be altered.
Licence and origin
Varnish is free software licensed under a two-clause BSD licence, also known as the FreeBSD licence. The project was initiated in 2005. Varnish Cache 1.0 was released in september 2006.
The name "Varnish"
The name Varnish comes from when the instigator of Varnish spent a long time staring at an art-poster with the word “Vernisage” and ended up checking it in a dictionary, which gives the following three meanings of the word:
r.v. var·nished, var·nish·ing, var·nish·es
- To cover with varnish.
- To give a smooth and glossy finish to.
- To give a deceptively attractive appearance to; gloss over.