Github user greghogan commented on the pull request:
https://github.com/apache/flink/pull/1067#issuecomment-135885866
I am currently running release-0.10.0-milestone-1.
Debugging with Eclipse and looking at MutableHashTable.initTable,
numBuckets is computed as 16086. There are 63 memory segments with 256 buckets
each = 16128 total buckets. The last 16128 - 16086 = 42 buckets are not
initialized by initTable which terminates the inner loop when bucket ==
numBuckets. Here is an example header dump from the last memory segment showing
the crossover from initialized to uninitialized data.
offset, partition, status, count, next-pointer
26880 10 0 0 -72340172838076673
27008 11 0 0 -72340172838076673
27136 12 0 0 -72340172838076673
27264 13 0 0 -72340172838076673
27392 0 -56 9 844425030795264
27520 0 -56 9 -9191846839379296256
27648 0 -56 9 10133099245469696
27776 0 -56 9 12103424082444288
Setting a breakpoint for MutableHashTable.buildBloomFilterForBucket for
count < 0, the last memory segment looked as follows (this is from a different
execution, operation, and thread).
offset, partition, status, count, next-pointer
26880 10 0 9 27584547767975936
27008 11 0 9 -9208735337998712832
27136 12 0 9 4503599694479360
27264 13 0 9 -9219994337067139072
27392 0 0 -32697 1161165883580435
27520 0 3 -15328 18016855230957176
27648 0 5 1388 -33740636012148672
27776 0 6 25494 -17363350186618861
MutableHashTable.buildBloomFilterForBucketsInPartition processed offset
27392 which happened to match the partition number and bucket status even
though it looks to be uninitialized.
After changing MutableHashTable.initTable to initialize all buckets in all
segments I have not seen the bug reoccur.
{code}
for (int k = 0; k < bucketsPerSegment /* && bucket < numBuckets*/; k++,
bucket++) {
}
{code}
I see at least three potential resolutions: 1) have
MutableHashTable.initTable initialize all buckets, 2) have
MutableHashTable.buildBloomFilterForBucket skip uninitialized buckets, or 3) I
have not looked enough at MutableHashTable.getInitialTableSize but it is
possible to completely fill the last segment with usable buckets?
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