This means that we could enable a feature that does a graceful cache serving, that when a cache is rebuilding, the subsequent connection will be then served with the stale copy.

This is to have to option to avoid a connection flood for highly active sites to be building multiple cache because one of of cached being expired, then there are parallel connection for the same url.

I hope the above explanation are clear, example to point to is the varnish's graceful cache.

I hope this is the right channel as well as. Sorry if it wasn't.