[Zope] Re: ZEO-Client

[Tim Peters]

[Tres Seaver]
> ...
> A minutes-long startup is likely due to the client's need to verify a
> large persistent disk cache;  one workaround would be to turn off
> persistent caches;  a longer-term solution would be to work with the
> folks on zodb-dev to land a set of improvements to the cache
> verification code (they live on a branch somewhere, I think).

All the cache verification speedups we had were released in ZODB 3.2
(see primarily "What's new in ZODB3 3.2 alpha 1" in

    http://zope.org/Products/ZODB3.2/NEWS

).  There aren't any more of those hiding on a branch.  There are
other kinds of optimizations hiding in assorted branches, though.

Having a "large" persistent ZEO cache has opposing effects: (a)
possibly better steady-state performance; (b) guaranteed longer
cold-start verification time.  That tradeoff is unavoidable with the
current design.  A possible future direction may be to use much larger
ZEO caches, but to weaken the meaning of "persistent" by simply giving
up after verification has consumed N seconds (throwing away all cached
objects that haven't managed to get verified by then).  There's no
code anywhere to do that now, though.