When computing absoluet guaranteed capacity (GC) from a percent value, Capacity
Scheduler should round up floats, rather than truncate them.
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Key: HADOOP-5003
URL: https://issues.apache.org/jira/browse/HADOOP-5003
Project: Hadoop Core
Issue Type: Bug
Reporter: Vivek Ratan
Priority: Minor
The Capacity Scheduler calculates a queue's absolute GC value by getting its
percent of the total cluster capacity (which is a float, since the configured
GC% is a float) and casting it to an int. Casting a float to an int always
rounds down. For very small clusters, this can result in the GC of a queue
being one lower than what it should be. For example, if Q1 has a GC of 50%, Q2
has a GC of 40%, and Q3 has a GC of 10%, and if the cluster capacity is 4 (as
we have, in our test cases), Q1's GC works out to 2, Q2's to 1, and Q3's to 0
with today's code. Q2's capacity should really be 2, as 40% of 4, rounded up,
should be 2.
Simple fix is to use Math.round() rather than cast to an int.
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