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From Mark Farnan <>
Subject Question about READS in a multi DC environment.
Date Sun, 11 May 2014 20:44:57 GMT
Im trying to understand READ load in Cassandra across a multi-datacenter cluster.   (Specifically
why it seems to be hitting more than one DC) and hope someone can help. 

From what Iím seeing here, a READ, with Consistency LOCAL_ONE,   seems to be hitting All
3 datacenters, rather than just the one Iím connected to.   I see  'Read 101 live and 0 tombstoned
cells'  from EACH of the 3 DC"s in the trace, which seems, wrong.     
I have tried every  Consistency level, same result.   This also is same from my C# code via
the DataStax driver, (where I first noticed the issue). 

Can someone please shed some light on what is occurring ?  Specifically I dont' want a query
on one DC, going anywhere near the other 2 as a rule, as in production,  these DC's will be
accross slower links. 

Query:  (NOTE:  Whilst this uses a kairosdb table,  i'm just playing with queries against
it as it has 100k columns in this key for testing). 

cqlsh:kairosdb> consistency local_one
Consistency level set to LOCAL_ONE.

cqlsh:kairosdb> select * from data_points where key = 0x6d61726c796e2e746573742e74656d70340000000145b514a400726f6f6d3d6f66666963653a
limit 1000;

... Some return data  rows listed here which I've removed ....

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