Re: [Libguestfs] [RFC nbdkit PATCH] multi-conn: New filter

On 2/24/21 11:33 AM, Eric Blake wrote: > Implement a TODO item of emulating multi-connection consistency via > multiple plugin flush calls to allow a client to assume that a flush > on a single connection is good enough. This also gives us some > fine-tuning over whether to advertise the bit, including some setups > that are unsafe but may be useful in timing tests. > > Testing is interesting: I used the sh plugin to implement a server > that intentionally keeps a per-connection cache. > > Note that this filter assumes that multiple connections will still > share the same data (other than caching effects); effects are not > guaranteed when trying to mix it with more exotic plugins like info > that violate that premise. > --- > > I'm still working on the test; the sh plugin is good enough that it > does what I want when playing with it manually, but I still need to > write up various scenarios in test-multi-conn.sh to match what I've > played with manually. > > I'm open to feedback on the set of options I've exposed during .config > (too many, not enough, better names?) Right now, it is: > multi-conn-mode=auto|plugin|disable|emulate|unsafe > multi-conn-track-dirty=fast|connection|off

Another thing I thought about: should I add a knob that lets multi-conn know whether export names are significant? When set, it only has to maintain consistency by flushing on other connections visiting the same export name, and not all connections.