Ryu Kobayashi created YARN-11964:
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Summary: Resource.castToIntSafely() should clamp negative values
to 0 to prevent propagation of invalid resource counts
Key: YARN-11964
URL: https://issues.apache.org/jira/browse/YARN-11964
Project: Hadoop YARN
Issue Type: Bug
Components: resourcemanager
Reporter: Ryu Kobayashi
h2. Problem
Resource.castToIntSafely() clamps values exceeding Integer.MAX_VALUE to
Integer.MAX_VALUE,
but silently passes through negative values. The method comment states
"This method assumes resource value is positive", however this assumption
is not guaranteed in practice.
When YARN RM temporarily reports negative available resources
(e.g. due to overload, node failures, or transient resource calculation
errors),
the negative value is propagated as-is to callers.
h2. Root Cause
The method only guards against positive overflow:
{code:java}
protected static int castToIntSafely(long value) {
if (value > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
}
return Long.valueOf(value).intValue();
}
{code}
There is no guard for negative values. When a negative long is passed,
it is returned as a negative int, which can cause unexpected behavior
in downstream components that assume resource values are non-negative.
h2. Impact
Downstream components that rely on this method receiving a non-negative int
may compute invalid results (e.g. negative slot counts, illegal collection
sizes)
when YARN temporarily reports negative available resources.
h2. Fix
Return 0 when value < 0, consistent with the existing behavior of
clamping out-of-range values to a safe boundary:
{code:java}
protected static int castToIntSafely(long value) {
if (value < 0) {
return 0;
}
if (value > Integer.MAX_VALUE) {
return Integer.MAX_VALUE;
}
return Long.valueOf(value).intValue();
}
{code}
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