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https://issues.apache.org/jira/browse/HBASE-15064?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15198769#comment-15198769
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ramkrishna.s.vasudevan commented on HBASE-15064:
------------------------------------------------
bq.because if somebody is trying to limit at the place which is exactly at the
boundary of the limitIndexBuffer then we are also including the last item which
does not have any data as you are limiting at 0 (as limit == limitedIndexBegin,
which is at the boundary), But then once you have read everything in the
previous buffer if the client consults hasRemaining function this will return
again true (as curIterm < no_of_items in array) but when you actually try to
read anything we will throw BufferUnderFlowException because again the last
element has no data.
This is again true. In case you see MBB as a generic API what you say is true
> BufferUnderflowException after last Cell fetched from an HFile Block served
> from L2 offheap cache
> -------------------------------------------------------------------------------------------------
>
> Key: HBASE-15064
> URL: https://issues.apache.org/jira/browse/HBASE-15064
> Project: HBase
> Issue Type: Bug
> Components: io
> Affects Versions: 2.0.0
> Reporter: deepankar
> Assignee: Anoop Sam John
> Priority: Critical
> Fix For: 2.0.0
>
> Attachments: HBASE-15064.patch
>
>
> While running the newer patches on our production system, I saw this error
> come couple of times
> {noformat}
> ipc.RpcServer: Unexpected throwable object
> 2016-01-01 16:42:56,090 ERROR
> [B.defaultRpcServer.handler=20,queue=20,port=60020] ipc.RpcServer: Unexpected
> throwable object
> java.nio.BufferUnderflowException
> at java.nio.Buffer.nextGetIndex(Buffer.java:500)
> at java.nio.DirectByteBuffer.get(DirectByteBuffer.java:249)
> at org.apache.hadoop.hbase.nio.MultiByteBuff.get(MultiByteBuff.java:494)
> at
> org.apache.hadoop.hbase.io.encoding.FastDiffDeltaEncoder$1.decode(FastDiffDeltaEncoder.java:402)
>
> at
> org.apache.hadoop.hbase.io.encoding.FastDiffDeltaEncoder$1.decodeNext(FastDiffDeltaEncoder.java:517)
>
> at
> org.apache.hadoop.hbase.io.encoding.BufferedDataBlockEncoder$BufferedEncodedSeeker.next(BufferedDataBlockEncoder.java:815)
> at
> org.apache.hadoop.hbase.regionserver.StoreFileScanner.next(StoreFileScanner.java:138)
> {noformat}
> Looking at the get code
> {code}
> if (this.curItem.remaining() == 0) {
> if (items.length - 1 == this.curItemIndex) {
> // means cur item is the last one and we wont be able to read a long.
> Throw exception
> throw new BufferUnderflowException();
> }
> this.curItemIndex++;
> this.curItem = this.items[this.curItemIndex];
> }
> return this.curItem.get();
> {code}
> Can the new currentItem have zero elements (position == limit), does it make
> sense to change the {{if}} to {{while}} ? {{while (this.curItem.remaining()
> == 0)}}. This logic is repeated may make sense abstract to a new function if
> we plan to change to {{if}} to {{while}}
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