Re: [exim] maildirsize file and massive concurrency

On 2011-02-16 at 23:32 +0100, Heiko Schlittermann wrote:
[ maildirsize recalculations expensive ]
> How is this solved on other busy sites?

A somewhat equivalent style of metadata caching (but not maildirsize) at
previous employment: you only care about the metadata at the time a user
connects to retrieve mail, so if the updates are frequent then rather
than updating every 5 minutes there's a new email, all night long, you
really care about having an update at the time of a new connection which
needs the data.

So let the POP/IMAP client update it on demand, with a scheme which can
scan the directories to find new messages to pull them in.

If need be, use a shadow_transport to write a flag-file to another
directory, or append to a per-injection-host logfile, or whatever, for
each new mail delivered. The client app can then pick up on those. For
reliability reasons (shadow_transport fails when mail delivery succeeds)
you probably want to randomly/daily force a complete scan anyway.

-Phil