[jira] [Commented] (HBASE-16643) Reverse scanner heap creation may not allow MSLAB closure due to inproper ref counting of segments
[
https://issues.apache.org/jira/browse/HBASE-16643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15509182#comment-15509182
]
Eshcar Hillel commented on HBASE-16643:
---
Hi [~ram_krish]
Could you please add a link to review board so it is easier to review the
patch. Thanks.
> Reverse scanner heap creation may not allow MSLAB closure due to inproper ref
> counting of segments
> --
>
> Key: HBASE-16643
> URL: https://issues.apache.org/jira/browse/HBASE-16643
> Project: HBase
> Issue Type: Bug
>Reporter: ramkrishna.s.vasudevan
>Assignee: ramkrishna.s.vasudevan
>Priority: Critical
> Fix For: 2.0.0
>
> Attachments: HBASE-16643.patch
>
>
> In the reverse scanner case,
> While doing 'initBackwardHeapIfNeeded' in MemstoreScanner for setting the
> backward heap, we do a
> {code}
> if ((backwardHeap == null) && (forwardHeap != null)) {
> forwardHeap.close();
> forwardHeap = null;
> // before building the heap seek for the relevant key on the scanners,
> // for the heap to be built from the scanners correctly
> for (KeyValueScanner scan : scanners) {
> if (toLast) {
> res |= scan.seekToLastRow();
> } else {
> res |= scan.backwardSeek(cell);
> }
> }
> {code}
> forwardHeap.close(). This would internally decrement the MSLAB ref counter
> for the current active segment and snapshot segment.
> When the scan is actually closed again we do close() and that will again
> decrement the count. Here chances are there that the count would go negative
> and hence the actual MSLAB closure that checks for refCount==0 will fail.
> Apart from this, when the refCount becomes 0 after the firstClose if any
> other thread requests to close the segment, then we will end up in corrupted
> segment because the segment could be put back to the MSLAB pool.
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[jira] [Commented] (HBASE-16643) Reverse scanner heap creation may not allow MSLAB closure due to inproper ref counting of segments
[
https://issues.apache.org/jira/browse/HBASE-16643?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel=15509011#comment-15509011
]
ramkrishna.s.vasudevan commented on HBASE-16643:
Now after this need to see if HBASE-15871 can be updated with a boolean
'closed' flag.
> Reverse scanner heap creation may not allow MSLAB closure due to inproper ref
> counting of segments
> --
>
> Key: HBASE-16643
> URL: https://issues.apache.org/jira/browse/HBASE-16643
> Project: HBase
> Issue Type: Bug
>Reporter: ramkrishna.s.vasudevan
>Assignee: ramkrishna.s.vasudevan
>Priority: Critical
> Fix For: 2.0.0
>
> Attachments: HBASE-16643.patch
>
>
> In the reverse scanner case,
> While doing 'initBackwardHeapIfNeeded' in MemstoreScanner for setting the
> backward heap, we do a
> {code}
> if ((backwardHeap == null) && (forwardHeap != null)) {
> forwardHeap.close();
> forwardHeap = null;
> // before building the heap seek for the relevant key on the scanners,
> // for the heap to be built from the scanners correctly
> for (KeyValueScanner scan : scanners) {
> if (toLast) {
> res |= scan.seekToLastRow();
> } else {
> res |= scan.backwardSeek(cell);
> }
> }
> {code}
> forwardHeap.close(). This would internally decrement the MSLAB ref counter
> for the current active segment and snapshot segment.
> When the scan is actually closed again we do close() and that will again
> decrement the count. Here chances are there that the count would go negative
> and hence the actual MSLAB closure that checks for refCount==0 will fail.
> Apart from this, when the refCount becomes 0 after the firstClose if any
> other thread requests to close the segment, then we will end up in corrupted
> segment because the segment could be put back to the MSLAB pool.
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