Project Lead | Wensong Zhang |
Site | http://www.LinuxVirtualServer.org/ |
Licence | GNU General Public Licence |
The Linux Virtual Server or Internet Protocol Virtual Server (IPVS) is an implementation, in the Linux kernel of layer 4 switching as described in section 4.2. The implementation supports direct routing, tunnelling and network address translation as forwarding methods. Least Connected, Weighted Least Connected, Round Robin and Weighted Round Robin scheduling algorithms are provided.
A daemon, ldirectord that ships as part of the Linux Virtual Server can be used to monitor the health of back-end servers if they are being used as web servers. ldirectord periodically requests a known page, checking that the response contains an expected string. If a web server fails then the server is taken out of the pool of real servers and will be reinserted once it comes back on line. If all the web servers are down then a fall-back server is inserted into the pool, which will be removed once one of the back-end web servers comes back on line. Typically the fall-back server will be localhost, running an Apache HTTP server that returns a page indicating that the service is temporarily inaccessible, for all URLs requested.