Hi Sunil,

Have you tried an alternate hashing function other than java hashcode that
might provide a more uniform distribution of your data? The google guava
library provides a set of hashing strategies, like murmur hash, that is
reported to have lesser hash collisions in different cases. Below is a link
explaining these from their website

https://github.com/google/guava/wiki/HashingExplained

Here is a link where someone has done a comparative study of different
hashing functions
http://programmers.stackexchange.com/questions/49550/which-hashing-algorithm-is-best-for-uniqueness-and-speed

If you end up choosing hashing function from google guava library, make
sure you use the documentation from guava version 11.0 as this version of
guava is already included in Hadoop classpath.

Thanks

On Fri, Oct 14, 2016 at 1:17 PM, Sunil Parmar <spar...@threatmetrix.com>
wrote:

> We’re using Stream codec to consistently / parallel processing of the data
> across the operator partitions. Our requirement is to serialize processing
> of the data based on particular tuple attribute let’s call it
> ‘catagory_name’ . In order to achieve the parallel processing of different
> category names we’re written our stream codec as following.
>
>    public class CatagoryStreamCodec extends 
> KryoSerializableStreamCodec<Object>
> {
>
> private static final long serialVersionUID = -687991492884005033L;
>
>
>
>     @Override
>
>     public int getPartition(Object in) {
>
>         try {
>
>         InputTuple tuple = (InputTuple) in;
>
> String partitionKehy = tuple.getName();
>
>         if(partitionKehy != null) {
>
> return partitionKehy.hashCode();
>
>         }
>
>     }
>    }
>
> It’s working as expected *but *we observed inconsistent partitions when
> we run this in production env with 20 partitioner of the operator following
> the codec in the dag.
>
>    - Some operator instance didn’t process any data
>    - Some operator instance process as many tuples as combined everybody
>    else
>
>
> Questions :
>
>    - getPartition method supposed to return the actual partition or just
>    some lower bit used for deciding partition ?
>    - Number of partitions is known to application properties and can vary
>    between deployments or environments. Is it best practice to use that
>    property in the stream codec ?
>    - Any recommended hash function for getting consistent variations in
>    the lower bit with less variety of data. we’ve ~100+ categories and I’m
>    thinking to have 10+ operator partitions.
>
>
> Thanks,
> Sunil
>

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