mongodb/mongo-hadoop — Issue #21: Mappers don't get data when using read_shard_chunks.
Author: yankov
Created: 2011-11-11 01:49:46+00:00
State: open

I'm using sharded MongoDb.

read_shard_chunks is set to true.
read_from_shards is set to false.

With any query for even small pieces of data mongo-hadoop creates tons of mapper tasks,
which don't receive any data (map input records = 0). However, if I set read_shard_chunks to false, everything works fine, but creates only single mapper task.