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xds: Fix WeakReference bug in SharedCallCounterMap #8466
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69eb4bc
add regression test
dapengzhang0 d46dd18
fix bug
dapengzhang0 50c637f
fix wrong fix
dapengzhang0 06cb848
fix comment
dapengzhang0 674500d
check ref before remove
dapengzhang0 01aa6be
manually call ref.enqueue()
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Original file line number | Diff line number | Diff line change |
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@@ -62,4 +62,22 @@ public boolean isDone() { | |
map.cleanQueue(); | ||
assertThat(counters).isEmpty(); | ||
} | ||
|
||
@Test | ||
public void gcAndRecreate() { | ||
@SuppressWarnings("UnusedVariable") // assign to null for GC only | ||
AtomicLong counter = map.getOrCreate(CLUSTER, EDS_SERVICE_NAME); | ||
final CounterReference ref = counters.get(CLUSTER).get(EDS_SERVICE_NAME); | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. FYI, you can call |
||
assertThat(counter.get()).isEqualTo(0); | ||
counter = null; | ||
GcFinalization.awaitDone(new FinalizationPredicate() { | ||
@Override | ||
public boolean isDone() { | ||
return ref.isEnqueued(); | ||
} | ||
}); | ||
map.getOrCreate(CLUSTER, EDS_SERVICE_NAME); | ||
assertThat(counters.get(CLUSTER)).isNotNull(); | ||
assertThat(counters.get(CLUSTER).get(EDS_SERVICE_NAME)).isNotNull(); | ||
} | ||
} |
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I'm guessing
clusterCounter
shouldn't be null, because refs should be enqueued in the same order as the order of underlying referents being nullified by garbage collector. But I did not see javadoc explicitly say that.Is there any risk of NPE in extreme race case like the following?
ref1.referent nullified by gc => ref2 created and put in the counters map => ref2.referent nullified by gc => ref2 enqueued => ref1 enqueued.
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With C1 it doesn't seem too far-fetched, especially if enqueuing is a separate stage of the process from clearing. I doubt it would actually happen, but it seems fair to consider.
A simple solution for that is to call
ref.enqueue()
ifref.get() == null
, before replacing the reference.There was a problem hiding this comment.
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Done. TIL thanks.