mdelete and Cache::Memcached::delete_multi()

[dormando]

> 
> Separate on/off are 100% safe only when on/off itself has a reply,
> hence the overhead.
> 
> Currently 'noreply' will still send the error if the command has wrong
> number of tokens, and thus no attempt is made to parse it (though I
> could parse it, I think that wouldn't be right).  To help this a bit
> we may add a startup option to the server, 'close_on_error', and use
> it for some errors that should never be ignored, so the error
> condition won't go unnoticed.

'silent' would be more useful for bulk imports. Do two roundtrips around
a bulk whatever, save from having to read.

I don't think a close on error condition should be used in this case. As
far as I'm concerned almost all errors should be transient... Especially
if you have a library like dustin's which might not multiplex the
connections.

Think the binary protocol would handle this a lot better via the client
opaque.

-Dormando