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From Jeremy Hanna <jeremy.hanna1...@gmail.com>
Subject Re: Updates lost
Date Tue, 30 Aug 2011 17:41:18 GMT
I would not use nano time with cassandra.  Internally and throughout the clients, milliseconds
is pretty much a standard.  You can get into trouble because when comparing nanoseconds with
milliseconds as long numbers, nanoseconds will always win.  That bit us a while back when
we deleted something and it couldn't come back because we deleted it with nanoseconds as the
timestamp value.

See the caveats for System.nanoTime() for why milliseconds is a standard:
http://download.oracle.com/javase/6/docs/api/java/lang/System.html#nanoTime%28%29

On Aug 30, 2011, at 12:31 PM, Jiang Chen wrote:

> Looks like the theory is correct for the java case at least.
> 
> The default timestamp precision of Pelops is millisecond. Hence the
> problem as explained by Peter. Once I supplied timestamps precise to
> microsecond (using System.nanoTime()), the problem went away.
> 
> I previously stated that sleeping for a few milliseconds didn't help.
> It was actually because of the precision of Java Thread.sleep().
> Sleeping for less than 15ms often doesn't sleep at all.
> 
> Haven't checked the Python side to see if it's similar situation.
> 
> Cheers.
> 
> Jiang
> 
> On Tue, Aug 30, 2011 at 9:57 AM, Jiang Chen <jiangc@gmail.com> wrote:
>> It's a single node. Thanks for the theory. I suspect part of it may
>> still be right. Will dig more.
>> 
>> On Tue, Aug 30, 2011 at 9:50 AM, Peter Schuller
>> <peter.schuller@infidyne.com> wrote:
>>>> The problem still happens with very high probability even when it
>>>> pauses for 5 milliseconds at every loop. If Pycassa uses microseconds
>>>> it can't be the cause. Also I have the same problem with a Java client
>>>> using Pelops.
>>> 
>>> You connect to localhost, but is that a single node or part of a
>>> cluster with RF > 1? If the latter, you need to use QUORUM consistency
>>> level to ensure that a read sees your write.
>>> 
>>> If it's a single node and not a pycassa / client issue, I don't know off hand.
>>> 
>>> --
>>> / Peter Schuller (@scode on twitter)
>>> 
>> 


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