net/pen 0.34.1 OpenBSD

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 (2048 by default). When the table is full, the least recently used one will be thrown out to make room for the new one. 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.

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 mergelogs solves this problem by merging pen's log file with the ones produced by the web servers.