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From lars hofhansl <lhofha...@yahoo.com>
Subject Re: HBase-0.94.2-SNAPSHOT Scanning Bug
Date Fri, 24 Aug 2012 01:21:33 GMT
I reverted that change for now.

----- Original Message -----
From: lars hofhansl <lhofhansl@yahoo.com>
To: "dev@hbase.apache.org" <dev@hbase.apache.org>
Sent: Thursday, August 23, 2012 6:05 PM
Subject: Re: HBase-0.94.2-SNAPSHOT Scanning Bug


"IPC Server handler 43 on 10304" daemon prio=10 tid=0x00007f16b8b1f000 nid=0x6414 runnable
   java.lang.Thread.State: RUNNABLE
    at org.apache.hadoop.hbase.KeyValue.createFirstOnRowColTS(KeyValue.java:1893)
    at org.apache.hadoop.hbase.regionserver.StoreFileScanner.requestSeek(StoreFileScanner.java:310)
    at org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:297)
    at org.apache.hadoop.hbase.regionserver.KeyValueHeap.requestSeek(KeyValueHeap.java:256)
    at org.apache.hadoop.hbase.regionserver.StoreScanner.reseek(StoreScanner.java:522)
    - locked <0x00000006cec5bd88> (a org.apache.hadoop.hbase.regionserver.StoreScanner)
    at org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner.doRealSeek(NonLazyKeyValueScanner.java:54)
    at org.apache.hadoop.hbase.regionserver.NonLazyKeyValueScanner.requestSeek(NonLazyKeyValueScanner.java:38)
    at org.apache.hadoop.hbase.regionserver.KeyValueHeap.generalizedSeek(KeyValueHeap.java:297)
    at org.apache.hadoop.hbase.regionserver.KeyValueHeap.requestSeek(KeyValueHeap.java:256)
    at org.apache.hadoop.hbase.regionserver.HRegion$RegionScannerImpl.nextRow(HRegion.java:3508)

points to my change: https://issues.apache.org/jira/browse/HBASE-6577

The trace is interesting: RegionScannerImpl.nextRow now seeks to the last KV in the row and
then iterates as before.
However, then the reseek internally seeks to the first KV of the column, and somehow this
interaction makes no progress forward.

I'll revert that change.

-- Lars

From: Elliott Clark <eclark@stumbleupon.com>
To: dev@hbase.apache.org 
Sent: Thursday, August 23, 2012 5:39 PM
Subject: HBase-0.94.2-SNAPSHOT Scanning Bug

I recently tried to update one of our clusters to a version of 0.94.2
seen here: https://github.com/stumbleupon/hbase/commits/su_prod_94

When doing that all of the nodes started taking all available cpu
time.  Not much interesting was in the logs however jstacks looked
like this: http://pastebin.com/raw.php?i=fw6P5RKE  Everything is
spinning in scans.  A version of 0.94.1 works perfectly and reverting
solved all issues.  I don't really have enough data to point at any
jira as the cause I was just wondering if anyone had some insight into
the few commits between 0.94.1 release and the head of the above
github that could cause scans to spin.


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