In order to decide when to pipeline requests (see Pipelining) and whether to perform Poor Man’s Multiplexing (see Poor Mans Multiplexing), Polipo needs to keep statistics about servers. These include the server’s ability to handle persistent connections, the server’s ability to handle pipelined requests, the round-trip time to the server, and the server’s transfer rate. The statistics are accessible from Polipo’s web interface (see Web interface).
The variable ‘serverExpireTime’ (default 1 day) specifies how
long such information remains valid. If a server has not been
accessed for a time interval of at least
information about it will be discarded.
As Polipo will eventually recover from incorrect information about a server, this value can be made fairly large. The reason why it exists at all is to limit the amount of memory used up by information about servers.