The on-disk cache consists in a filesystem subtree rooted at a
location defined by the variable diskCacheRoot
, by default
"/var/cache/polipo/"
. This directory should normally be
writeable, readable and seekable by the user running Polipo. It
should normally point at a local filesystem; however, using NFSv3
should be safe in most implementations, but NFSv2 is definitely
not1.
Polipo will accept to use a read-only cache. Note, however, that using Polipo in this manner will prevent it from updating usage information of on-disk objects, which will make purge control problematic (see Purging).
If diskCacheRoot
is an empty string, no disk cache is used.
The value maxDiskEntries
(32 by default) is the absolute
maximum of file descriptors held open for on-disk objects. When this
limit is reached, Polipo will close descriptors on a
least-recently-used basis, which will cause no harm other than a
decrease in performance. This value should be set to be larger than
the number of resources that you expect to be live at a single time;
defining the right notion of liveness is left as an exercise for the
reader.
The value diskCacheWriteoutOnClose
(32KB by default) is
the amount of data that Polipo will write out when closing a disk
file. Writing out data when closing a file can avoid subsequently
reopening and validating it, but causes unnecessary work if the
instance is later superseded.
The integers diskCacheDirectoryPermissions
and
diskCacheFilePermissions
are the Unix filesystem permissions
with which files and directories are created in the on-disk cache.