[ZODB-Dev] newbie ZEO first try. ConflictError.

[tsmiller]

James,
You were right.  I moved the assignment into the inner loop where is is
reassigned each time after the abort.  However, if I do not put the abort()
in, then the ZODB comes back with a ConflictError and actually dies with a
TransactionFailedError.  The commit() is the purpose of the entire thing. 
To save my changes to the database.  And if the commit() does not work the
first time, then the loop waits a little while and trys the commit() again.

I have two programs now so that I could differentiate which one was actually
committing, and I still get a ConflictError every time a transaction is
tried.


    while True:
            while True:
                    ## one program prints out program 1 and the other
program 2 to show origin of commit
                    root[ "one" ] = "program 2 - " + time.asctime()
                    try:
                            print "Try to commit transaction"
                            transaction.commit()
                            print "root is",  root
                    except POSException.ConflictError:
                            print "we have a conflict"
                            transaction.abort()
                            time.sleep(.2)
                    else:
                            break

            time.sleep(10)


output:

we have a conflict
Try to commit transaction
root is {'one': 'program 2 - Thu Nov 26 14:29:02 2009'}
Try to commit transaction
we have a conflict
Try to commit transaction
root is {'one': 'program 2 - Thu Nov 26 14:29:12 2009'}
Try to commit transaction
we have a conflict
Try to commit transaction
root is {'one': 'program 2 - Thu Nov 26 14:29:22 2009'}
Try to commit transaction
we have a conflict




James Bergstra-2 wrote:
> 
> On Thu, Nov 26, 2009 at 1:51 PM, tsmiller <tsmiller at gnixterhouse.com>
> wrote:
>>
>> Laurence,
>> Thank you for your very quick reply.  I did as you suggested and now the
>> ConflictError is now handled.  And that is a most excellent thing because
>> now ConflictError is raised every time.  So it still seems to be
>> confused.
>> I am trying to figure out if I will be able to use ZEO in my application.
>>
>> Now my program reads:
>>
>> while True:
>>        root[ "one" ] = time.asctime()
>>        while True:
>>                try:
>>                        print "Try to commit transaction"
>>                        transaction.commit()
>>                        print "root is",  root
>>                except POSException.ConflictError:
>>                        print "we have a conflict"
>>                        transaction.abort()
>>                        time.sleep(.2)
>>                else:
>>                        break
>>
>>        time.sleep(10)
>>
> 
> I have a related question about this code... in the inner loop tom is
> calling abort() ; sleep(); commit().  Does that make sense?
> 
> I thought that abort() would revert the root to the database's version
> of things, and discard any change that the client had tried to make.
> So what does it mean to call commit() again immediately and why that
> commit cause a conflict when the client hasn't actually changed
> anything since abort() ?
> 
> James
> -- 
> http://www-etud.iro.umontreal.ca/~bergstrj
> _______________________________________________
> For more information about ZODB, see the ZODB Wiki:
> http://www.zope.org/Wikis/ZODB/
> 
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> 
> 

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