The WARN messages are the "emergency pressure valve" kicking in, search for 
that test in conf/cassandra.yaml. These are settings to reduce the chance of 
going OOM. It means you should take a look at your memtable and cache settings 
as you are getting close to running out of memory. 

Jonathan or Sylvain will have a better idea of why/how the error is occurring. 

But if you wanted to get fresh data on the node, a simple approach is to 
delete/move just the SSTable that is causing problems then run a repair. That 
should reduce the amount of data that needs to be moved. 

Hope that helps.
Aaron

On 11 Apr 2011, at 00:15, Jonathan Colby wrote:

> It appears we have several unserializable or unreadable rows.  These were not 
> fixed even after doing a "scrub"  on all nodes -  even though the scrub 
> seemed to have completed successfully.
> 
> I trying to fix these by doing a "repair", but these exceptions are thrown 
> exactly when doing a repair.   Anyone run into this issue?  What's the best 
> way to fix this?  
> 
> I was thinking that flushing and reloading the data with a move (reusing the 
> same token) might be a way to get out of this.
> 
> 
> Exception seem multiple times for different keys during a repair:
> 
> ERROR [CompactionExecutor:1] 2011-04-10 14:05:55,528 PrecompactedRow.java 
> (line 82) Skipping row DecoratedKey(58054163627659284217684165071269705317, 
> 64396663313763662d383432622d343439652d623761312d643164663936333738306565) in 
> /var/lib/cassandra/data/DFS/main-f-232-Data.db
> java.io.EOFException
>       at java.io.RandomAccessFile.readFully(RandomAccessFile.java:383)
>       at java.io.RandomAccessFile.readFully(RandomAccessFile.java:361)
>       at 
> org.apache.cassandra.io.util.BufferedRandomAccessFile.readBytes(BufferedRandomAccessFile.java:268)
>       at 
> org.apache.cassandra.utils.ByteBufferUtil.read(ByteBufferUtil.java:310)
>       at 
> org.apache.cassandra.utils.ByteBufferUtil.readWithLength(ByteBufferUtil.java:267)
>       at 
> org.apache.cassandra.db.ColumnSerializer.deserialize(ColumnSerializer.java:94)
>       at 
> org.apache.cassandra.db.ColumnSerializer.deserialize(ColumnSerializer.java:35)
>       at 
> org.apache.cassandra.db.ColumnFamilySerializer.deserializeColumns(ColumnFamilySerializer.java:129)
>       at 
> org.apache.cassandra.io.sstable.SSTableIdentityIterator.getColumnFamilyWithColumns(SSTableIdentityIterator.java:176)
>       at 
> org.apache.cassandra.io.PrecompactedRow.<init>(PrecompactedRow.java:78)
>       at 
> org.apache.cassandra.io.CompactionIterator.getCompactedRow(CompactionIterator.java:139)
>       at 
> org.apache.cassandra.io.CompactionIterator.getReduced(CompactionIterator.java:108)
>       at 
> org.apache.cassandra.io.CompactionIterator.getReduced(CompactionIterator.java:43)
>       at 
> org.apache.cassandra.utils.ReducingIterator.computeNext(ReducingIterator.java:73)
>       at 
> com.google.common.collect.AbstractIterator.tryToComputeNext(AbstractIterator.java:136)
>       at 
> com.google.common.collect.AbstractIterator.hasNext(AbstractIterator.java:131)
>       at 
> org.apache.commons.collections.iterators.FilterIterator.setNextObject(FilterIterator.java:183)
>       at 
> org.apache.commons.collections.iterators.FilterIterator.hasNext(FilterIterator.java:94)
>       at 
> org.apache.cassandra.db.CompactionManager.doValidationCompaction(CompactionManager.java:803)
>       at 
> org.apache.cassandra.db.CompactionManager.access$800(CompactionManager.java:56)
>       at 
> org.apache.cassandra.db.CompactionManager$6.call(CompactionManager.java:358)
>       at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
>       at java.util.concurrent.FutureTask.run(FutureTask.java:138)
>       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)
> 
> 
> This WARN also seems to come up often during a repair.  Not sure if it 
> related to this problem:
> 
> WARN [ScheduledTasks:1] 2011-04-10 14:10:24,991 GCInspector.java (line 149) 
> Heap is 0.8675910480028087 full.  You may need to reduce memtable and/or 
> cache sizes.  Cassandra will now flush up to the two largest memtables to 
> free up memory.  Adjust flush_largest_memtables_at threshold in 
> cassandra.yaml if you don't want Cassandra to do this automatically
> WARN [ScheduledTasks:1] 2011-04-10 14:10:24,992 StorageService.java (line 
> 2206) Flushing ColumnFamilyStore(table='DFS', columnFamily='main') to relieve 
> memory pressure
> INFO [ScheduledTasks:1] 2011-04-10 14:10:24,992 ColumnFamilyStore.java (line 
> 695) switching in a fresh Memtable for main at 
> CommitLogContext(file='/var/lib/cassandra/commitlog/CommitLog-1302435708131.log',
>  position=28257053)
> 

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