SoftValueSortedMap is broken, can generate NPEs
-----------------------------------------------
Key: HBASE-2909
URL: https://issues.apache.org/jira/browse/HBASE-2909
Project: HBase
Issue Type: Bug
Components: client
Affects Versions: 0.89.20100621, 0.20.6
Reporter: Jean-Daniel Cryans
Priority: Blocker
Fix For: 0.20.7, 0.90.0
The way SoftValueSortedMap is using SoftValues, it looks like that it's able to
get it's keys garbage collected along with the values themselves. We got this
issue in production but I was also able to randomly generate it using YCSB with
300 threads. Here's an example on 0.20 with jdk 1.6u14:
{noformat}
java.lang.NullPointerException
at org.apache.hadoop.hbase.util.Bytes.compareTo(Bytes.java:1036)
at
org.apache.hadoop.hbase.util.Bytes$ByteArrayComparator.compare(Bytes.java:104)
at
org.apache.hadoop.hbase.util.Bytes$ByteArrayComparator.compare(Bytes.java:96)
at java.util.TreeMap.cmp(TreeMap.java:1911)
at java.util.TreeMap.get(TreeMap.java:1835)
at
org.apache.hadoop.hbase.util.SoftValueSortedMap.get(SoftValueSortedMap.java:91)
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers.getCachedLocation(HConnectionManager.java:788)
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegionInMeta(HConnectionManager.java:651)
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:634)
at
org.apache.hadoop.hbase.client.HConnectionManager$TableServers.locateRegion(HConnectionManager.java:601)
at org.apache.hadoop.hbase.client.HTable.<init>(HTable.java:128)
at
org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.getTable(ThriftServer.java:262)
at
org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.mutateRowTs(ThriftServer.java:585)
at
org.apache.hadoop.hbase.thrift.ThriftServer$HBaseHandler.mutateRow(ThriftServer.java:578)
at
org.apache.hadoop.hbase.thrift.generated.Hbase$Processor$mutateRow.process(Hbase.java:2345)
at
org.apache.hadoop.hbase.thrift.generated.Hbase$Processor.process(Hbase.java:1988)
at
org.apache.thrift.server.TThreadPoolServer$WorkerProcess.run(TThreadPoolServer.java:259)
at
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
at
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
at java.lang.Thread.run(Thread.java:619)
{noformat}
In this specific case, the null cannot be the passed key because it's coming
from HTable which uses HConstants.EMPTY_START_ROW. It cannot be a null key that
was inserted previously because we would have got the NPE at insert time. This
can only mean that some key *became* null.
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