[ZWeb] ratings redux

[Kapil Thangavelu]

--- Paul Everitt <paul@zope.com> wrote:
> 
> Does the IIBTree, along with hashing by username,
> make this better 
> optimized for conflict errors and ZEO use?

it can help with write conflicts, be benefiting from
the resolution already in the btree code and the
separation into buckets. ZEO usage in general tends to
magnify hotspots. Compared to the alternatives this
technique seems best suited for scaling if the storage
is the zodb.

>  I
> suppose it also makes ZODB 
>   bloat less of a problem, because a smaller
> structure is being written to.

yes, the internal storage of the IIBTree is smaller
than a corresponding python version. although, if you
add in consideration of mounted nonundoable storages
and compare to the size bloat from multiple revisions
in a undoable storage, things become less clear. this
existing implementation is not well suited to that,
since ratings are stored local to content. but i had a
requirement that ratings would not be lost from object
movement, which without a general object linking
service would have been problematic for a centralized
storage using path references to content.

> How related is this implementation strategy to one
> for hit counters? 
> The username as the key obviously would help much
> less.

a different approach for counters would be taken, i
assume you mean download counters. in such a case a
BTrees Length object could be used directly as a hit
counter, as it supports write and read conflict
resolution, and its state is saved as just an integer
and a class ref.

cheers

kapil


> 
> --Paul
> 
> Kapil Thangavelu wrote:
> > i've upload a new version of the ratings product,
> that
> > now includes a cmf tool.
> > 
> >
>
http://www.zope.org/Members/k_vertigo/Products/Ratings
> > 
> > a word of warning, the tool hasn't gotten much
> > testing.
> > 
> > cheers
> > 
> > kapil
> > 
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