The replication lag affects actual entity data as well as indexes.

--
Ikai Lan
Developer Programs Engineer, Google App Engine
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On Fri, Jan 7, 2011 at 12:05 PM, Waldemar Kornewald <[email protected]>wrote:

> Hi Ikai,
>
> On Friday, January 7, 2011 12:09:24 AM UTC+1, Ikai Lan (Google) wrote:
>>
>> Hey guys, some answers to your questions that we've compiled from various
>> team members (mostly Alfred, presenter of "Next Gen Queries" and the fourth
>> one from the left in this video
>> http://www.youtube.com/watch?v=dg0TEIRQePg):
>>
>> - Typically, how long does it take for HR query data to become consistent
>> (a ballpark figure)?
>>
>> 100ms is the estimate. However - we have seen cases where this can be
>> higher. If you were to use the eventual consistency read option in the
>> master-slave configuration, we've seen that the average replication lag is
>> about 3 minutes with an upper bound of 10 minutes.
>>
>
> Does the eventual consistency lag only affect DB indexes (i.e. the query
> results contain up-to-date entities as if fetched via db.get(), but they
> might not really match the query, anymore)? Or does the lag affect the
> actual entity data returned by the query (i.e. the results contain
> *outdated* entities, IOW returning older data than db.get())?
>
> Bye,
> Waldemar Kornewald
>
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