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https://issues.apache.org/jira/browse/HBASE-16737?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15536161#comment-15536161
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Mark Christiaens commented on HBASE-16737:
------------------------------------------
[~anoop.hbase] The call through {{preScannerClose}} seems OK to me.
To me, this code looks surprising
(org.apache.hadoop.hbase.regionserver.KeyValueHeap#close):
{noformat}
public void close() {
if (this.current != null) {
this.current.close();
}
if (this.heap != null) {
KeyValueScanner scanner;
while ((scanner = this.heap.poll()) != null) {
scanner.close();
}
}
}
{noformat}
Looks like it wants to close all scanners that are in the {{heap}}. Instead of
iterating over them and closing them, the code performs a _poll_ to get them?
> NPE during close of RegionScanner
> ---------------------------------
>
> Key: HBASE-16737
> URL: https://issues.apache.org/jira/browse/HBASE-16737
> Project: HBase
> Issue Type: Bug
> Affects Versions: 1.0.0
> Reporter: Mark Christiaens
>
> We encountered the following stack trace during high load:
> {noformat}
> Unexpected throwable object
> java.lang.NullPointerException
> at
> org.apache.hadoop.hbase.CellComparator.compareRows(CellComparator.java:186)
> at
> org.apache.hadoop.hbase.CellComparator.compare(CellComparator.java:63)
> at
> org.apache.hadoop.hbase.KeyValue$KVComparator.compare(KeyValue.java:2021)
> at
> org.apache.hadoop.hbase.regionserver.KeyValueHeap$KVScannerComparator.compare(KeyValueHeap.java:202)
> at
> org.apache.hadoop.hbase.regionserver.KeyValueHeap$KVScannerComparator.compare(KeyValueHeap.java:178)
> at
> org.apache.hadoop.hbase.regionserver.KeyValueHeap$KVScannerComparator.compare(KeyValueHeap.java:168)
> at
> java.util.PriorityQueue.siftDownUsingComparator(PriorityQueue.java:719)
> at java.util.PriorityQueue.siftDown(PriorityQueue.java:687)
> at java.util.PriorityQueue.poll(PriorityQueue.java:595)
> at
> org.apache.hadoop.hbase.regionserver.KeyValueHeap.close(KeyValueHeap.java:218)
> at
> org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.close(HRegion.java:5608)
> at
> org.apache.phoenix.coprocessor.BaseScannerRegionObserver$2.close(BaseScannerRegionObserver.java:279)
> at
> org.apache.phoenix.coprocessor.BaseScannerRegionObserver$1.close(BaseScannerRegionObserver.java:186)
> at
> org.apache.hadoop.hbase.regionserver.RSRpcServices.scan(RSRpcServices.java:2378)
> at
> org.apache.hadoop.hbase.protobuf.generated.ClientProtos$ClientService$2.callBlockingMethod(ClientProtos.java:32205)
> at org.apache.hadoop.hbase.ipc.RpcServer.call(RpcServer.java:2034)
> at org.apache.hadoop.hbase.ipc.CallRunner.run(CallRunner.java:107)
> at
> org.apache.hadoop.hbase.ipc.RpcExecutor.consumerLoop(RpcExecutor.java:130)
> at org.apache.hadoop.hbase.ipc.RpcExecutor$1.run(RpcExecutor.java:107)
> at java.lang.Thread.run(Thread.java:745)
> {noformat}
> What I suspect is happening is that the {{RegionScannerImpl}} is being closed
> while the scanner's lease is expired. During this close, the underlying
> {{KeyValueHeap}} is being polled. the {{heap}} tries to read data from
> {{KeyValueScanners}} that then return {{null}} which causes the crash.
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