Paul Rogers created DRILL-5158:
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Summary: BootStrapContext has scan thread size set to large for
embedded
Key: DRILL-5158
URL: https://issues.apache.org/jira/browse/DRILL-5158
Project: Apache Drill
Issue Type: Improvement
Affects Versions: 1.9.0
Reporter: Paul Rogers
Assignee: Parth Chandra
Priority: Trivial
The Parquet async project added a new config setting: the number of scan
threads. But, the hard-coded minimum is too large for an embedded Drillbit on a
Mac used for unit tests.
In {{BootStrapContext}}:
{code}
private static final int MIN_SCAN_THREADPOOL_SIZE = 8; // Magic num
...
final int numScanThreads = (int)
(config.getDouble(ExecConstants.SCAN_THREADPOOL_SIZE));
...
final int scanThreadPoolSize =
MIN_SCAN_THREADPOOL_SIZE > numScanThreads ? MIN_SCAN_THREADPOOL_SIZE :
numScanThreads;
{code}
Effectively, this code says you can have as small a thread pool as you like as
long as it is 8 or greater.
Empirically, a thread pool size of 2 (set by altering the above code) caused
the Drillbit to hang. A size of 4 allowed the Drillbit to run.
In theory, a size of 0 should be fine as long as the code does not use Parquet
(or use the async reader). A pool size of 2 should work, but be slow (compared
to a larger size.)
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