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From Paul Loy <ketera...@gmail.com>
Subject Re: Updates lost
Date Thu, 01 Sep 2011 22:30:40 GMT
Well, on windows Vista and below (haven't checked on 7),
System.currentTimeMillis only has around 10ms granularity. That is for any
10ms period, you get the same value. I develop on Windows and I'd get
sporadic integration test failures due to this.

On Thu, Sep 1, 2011 at 8:31 PM, Jeremiah Jordan <
jeremiah.jordan@morningstar.com> wrote:

> Are you running on windows?  If the default timestamp is just using
> time.time()*1e6 you will get the same timestamp twice if the code is close
> together.  time.time() on windows is only millisecond resolution.  I don't
> use pycassa, but in the Thrift api wrapper I created for our python code I
> implemented the following function for getting timestamps:
>
> def GetTimeInMicroSec():
>    """
>    Returns the current time in microseconds, returned value always
> increases with each call.
>
>    :return: Current time in microseconds
>    """
>    newTime = long(time.time()*1e6)
>    try:
>        if GetTimeInMicroSec.lastTime >= newTime:
>            newTime = GetTimeInMicroSec.lastTime + 1
>    except AttributeError:
>        pass
>    GetTimeInMicroSec.lastTime = newTime
>    return newTime
>
>
> On 08/29/2011 04:56 PM, Peter Schuller wrote:
>
>> If the client sleeps for a few ms at each loop, the success rate
>>> increases. At 15 ms, the script always succeeds so far. Interestingly,
>>> the problem seems to be sensitive to alphabetical order. Updating the
>>> value from 'aaa' to 'bbb' never has problem. No pause needed.
>>>
>> Is it possible the version of pycassa you're using does not guarantee
>> that successive queries use non-identical and monotonically increasing
>> timestamps? I'm just speculating, but if that is the case and two
>> requests are sent with the same timestamp (due to resolution being
>> lower than the time it takes between calls), the tie breaking would be
>> the column value which jives with the fact that you're saying it seems
>> to depend on the value.
>>
>> (I haven't checked current nor past versions of pycassa to determine
>> if this is plausible. Just speculating.)
>>
>>


-- 
---------------------------------------------
Paul Loy
paul@keteracel.com
http://uk.linkedin.com/in/paulloy

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