Different results to same queries

Sadykov Rustem sadrust at gmail.com
Tue May 5 05:44:39 EDT 2015


Hi.
I've increased number of JS machines for map and reduce to 32 and now I don't get this strange behaviour (now on every query I get same results count), so it looks like the problem is solved on riak 1.4.10, but I still get different results when I try to use riak 2.1.0 (even if I increase number of JS machines there).
Looks like I have to stop using map-reduce in riak 2.1.0

On May 4, 2015, at 7:40 PM, Christopher Meiklejohn <cmeiklejohn at basho.com> wrote:

> 
>> On Apr 22, 2015, at 6:45 PM, Sadykov Rustem <sadrust at gmail.com> wrote:
>> 
>> Hello.
>> I'm testing riak 1.4.10 on 2 node cluster (on different servers), but result is same on 3 nodes cluster and on single node also.
>> 
>> I try to count records in my bucket and always get 3-4 different results.
>> Query is:
>> 
>> curl -XPOST http://localhost:8098/mapred -H 'Content-Type: application/json' -d '{"inputs":"account", "query":[{"reduce":{"language":"erlang", "module":"riak_kv_mapreduce", "function":"reduce_count_inputs", "arg":{"reduce_phase_batch_size":1000} } }] }’
> 
> Hi Sadykov,
> 
> Map/Reduce chooses one replica for each value to execute the query on during a distributed Map/Reduce job.  Given that, subsequent executions might occur on different replicas given the coverage plan chosen during that period.
> 
> That said, can you provide information on when you are writing the values you are running the job against?  For example, are you writing to a quorum of nodes right before the query?  It’s possible to see some staleness if you are using majority quorums and you are executing against replicas that are delayed due to network traffic.
> 
> - Chris
> 
> Christopher Meiklejohn
> Senior Software Engineer
> Basho Technologies, Inc.
> cmeiklejohn at basho.com
> 

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