[Grok-dev] Re: Apache support for Grok

[Martijn Faassen]

Laurence Rowe wrote:
> Well as I have looked into this fairly recently perhaps this summary can 
> help.
> 
> PGStorage is a full ZODB storage (supporting undo and packing but not 
> zodb level versions, which no one uses anyway). It also replaces the ZEO 
> layer. It subclasses the connection to provide per thread connections. 
> This means that it replaces ZEO and MVCC is performed by postgresql. It 
> stores pickles in the database so is conceptually fairly simple. It 
> depends on Postgres 8.1 or later.
> 
> Performance considerations (this is based on gut instinct rather than 
> testing!)
> 
>  * ZEO performs conflict resolution on the ZEO server rather than the 
> ZEO client. As far as I know only ZODB BTress have conflict resolution 
> code. This could be a problem for PGStorage in high concurrent write 
> situations where network latency could become an issue.
> 
>  * PGStorage leverages the postgres networking layer which (according to 
> pgstorage.sf.net) gives it an edge against ZEO + FileStorage in simple 
> benchmarks.
> 
> I'm not aware of any production use of PGStorage.

Cool; thanks for the summary - I only just saw it! So it looks like 
PGStorage would be a good candidate to try for an Apache version of Zope 
  3/Grok.

I wonder how much it depends on PostgreSQL specific features; 
unfortunately most hosting setups offer MySQL.

Regards,

Martijn