sorting - What's the fastest approach to merging a small number of large, already sorted lists in Hadoop? -



sorting - What's the fastest approach to merging a small number of large, already sorted lists in Hadoop? -

i've got little hadoop (cdh5.1.0, mrv2/yarn) cluster (5x nodes 4cpu, 16gb ram, 600gb disk) of contains little number ~30 of ~15gb sequencefiles. sequencefiles contains pairs of byteswritable/byteswritable, , keys not uniformly distributed across possible keyspace - it's rather lumpy. however, these files sorted.

i need merge these create single, sorted sequencefile, efficiently possible. i've tried number of approaches already, haven't been successful.

initially, tried using mapreduce job randomsampler , totalorderpartitioner, , around 1000 reducers. however, turns out because of non-uniformity of input keys, randomsampler isn't @ distributing info across partitions, , end 999 reducers succeeding, , 1 failing due running out of local disk.

it occurs me approach doesn't appear take advantage of fact input info sorted - solve problem if input info in random order.

i notice there's sequencefile.sorter class aims merge sequencefiles single sorted output. while single-threaded process, improve mr approach? there different mr approach take exploit fact input info sorted? seem fastest way simple merge, there way in parallel across cluster?

sorting hadoop mapreduce

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