[ZODB-Dev] transaction observer iface

[Shane Hathaway]

On Fri, 20 Feb 2004, John Belmonte wrote:

> Shane Hathaway wrote:
> > Every transaction participant is already an observer, isn't it?  It seems
> > like the only functionality you added is notifyObjectRegistered();  
> > everything else is accessible through tpc_*.  Maybe I misinterpreted.
> 
> Would you please explain how to use that interface (and what "tpc" 
> stands for)?

TPC stands for two-phase commit.  Look at the CommitVersion class in
ZODB/DB.py.  It implements the tpc_* methods, commit(), and abort().  You
can create a CommitVersion instance and register it to become part of the
transaction by calling get_transaction().register(my_commitversion).  
Once registered, the object will be notified of changes to the
transaction's state.  CommitVersion uses the notifications to commit or
abort a large change to the database.

Note that CommitVersion does not implement Persistent.  This is important.  
If you register a Persistent object with a transaction, the transaction
assumes that you want the object's _p_jar to receive the notifications.  
If you want to receive notifications directly, don't subclass Persistent.

Shane