Michael Ho created IMPALA-8341:
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             Summary: Data cache for remote reads
                 Key: IMPALA-8341
                 URL: https://issues.apache.org/jira/browse/IMPALA-8341
             Project: IMPALA
          Issue Type: Improvement
          Components: Backend
    Affects Versions: Impala 3.2.0
            Reporter: Michael Ho
            Assignee: Michael Ho


When running in public cloud (e.g. AWS with S3) or in certain private cloud 
settings (e.g. data stored in object store), the computation and storage are no 
longer co-located. This breaks the typical pattern in which Impala query 
fragment instances are scheduled at where the data is located. In this setting, 
the network bandwidth requirement of both the nics and the top of rack switches 
will go up quite a lot as the network traffic includes the data fetch in 
addition to the shuffling exchange traffic of intermediate results.

To mitigate the pressure on the network, one can build a storage backed cache 
at the compute nodes to cache the working set. With deterministic scan range 
scheduling, each compute node should hold non-overlapping partitions of the 
data set. 

A prototype of the cache was posted here: https://gerrit.cloudera.org/#/c/12683/



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