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https://issues.apache.org/jira/browse/CASSANDRA-4687?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13501351#comment-13501351
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Jeremy Hanna commented on CASSANDRA-4687:
-----------------------------------------

As another data point, one user reported seeing the cache capacity misreporting 
its value in the nodetool info output around the same time as seeing the 
DecoratedKey exceptions in their log.  Once they readjusted the cache capacity 
using nodetool setcachecapacity, the exceptions went away.  They set both key 
and row cache to non-zero values, so it looks like disabling key cache, at 
least for them, wasn't necessary.

So for example, they had 1024M for key cache and 1024M for row cache in the 
cassandra.yaml.  They saw values like the following when running nodetool info 
on a few of the nodes:
{quote}
Key Cache        : size 536870880 (bytes), capacity 536870880 (bytes), 81039812 
hits, 95996835 requests, 0.879 recent hit rate, 14400 save period in seconds
Row Cache        : size 237336 (bytes), capacity 238282 (bytes), 823752 hits, 
1171017 requests, 0.687 recent hit rate, 0 save period in seconds
{quote}
Note that the capacity value is far below what they configured in their 
cassandra.yaml.
                
> Exception: DecoratedKey(xxx, yyy) != DecoratedKey(zzz, kkk)
> -----------------------------------------------------------
>
>                 Key: CASSANDRA-4687
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-4687
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 1.1.5
>         Environment: CentOS 6.3 64-bit, Oracle JRE 1.6.0.33 64-bit, single 
> node cluster
>            Reporter: Leonid Shalupov
>            Assignee: Pavel Yaskevich
>             Fix For: 1.1.7
>
>         Attachments: 4687-debugging.txt
>
>
> Under heavy write load sometimes cassandra fails with assertion error.
> git bisect leads to commit 295aedb278e7a495213241b66bc46d763fd4ce66.
> works fine if global key/row caches disabled in code.
> {quote}
> java.lang.AssertionError: DecoratedKey(xxx, yyy) != DecoratedKey(zzz, kkk) in 
> /var/lib/cassandra/data/...-he-1-Data.db
>       at 
> org.apache.cassandra.db.columniterator.SSTableSliceIterator.<init>(SSTableSliceIterator.java:60)
>       at 
> org.apache.cassandra.db.filter.SliceQueryFilter.getSSTableColumnIterator(SliceQueryFilter.java:67)
>       at 
> org.apache.cassandra.db.filter.QueryFilter.getSSTableColumnIterator(QueryFilter.java:79)
>       at 
> org.apache.cassandra.db.CollationController.collectAllData(CollationController.java:256)
>       at 
> org.apache.cassandra.db.CollationController.getTopLevelColumns(CollationController.java:64)
>       at 
> org.apache.cassandra.db.ColumnFamilyStore.getTopLevelColumns(ColumnFamilyStore.java:1345)
>       at 
> org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1207)
>       at 
> org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1142)
>       at org.apache.cassandra.db.Table.getRow(Table.java:378)
>       at 
> org.apache.cassandra.db.SliceFromReadCommand.getRow(SliceFromReadCommand.java:69)
>       at 
> org.apache.cassandra.service.StorageProxy$LocalReadRunnable.runMayThrow(StorageProxy.java:819)
>       at 
> org.apache.cassandra.service.StorageProxy$DroppableRunnable.run(StorageProxy.java:1253)
>       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:662)
> {quote}

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