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From "Jignesh Dhruv (JIRA)" <j...@apache.org>
Subject [jira] Commented: (CASSANDRA-1130) Cassandra throws Exceptions at startup when using TTL in SuperColumns
Date Tue, 25 May 2010 20:39:34 GMT

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Jignesh Dhruv commented on CASSANDRA-1130:
------------------------------------------

OK. I think I narrowed it down further..

The bug may be in "org/apache/cassandra/db/filter/SSTableSliceIterator.java:getNextBlock()
method.

See the while loop on line 233.
Out here, its reading 1 column at a time.

As I said before, the problem is when an Column of Type ExpiringColumn becomes DeletedColumn
when time has expired.

In that case, once the Supercolumn whose subcolumns are of type "DELETED" are read in this
while loop, there are some extra bytes that needs to be skipped but instead it goes in the
second iteration in the while loop and tries to read the next column and thats where all the
problem starts.

Shouldn't the while loop just read one Column at a time and then exit. That is what it does
when it reads all the bytes. If I put a "break statement" in the end of while loop after reading
a column all works fine as the extra bytes are skipped during the next read of a Column.

I am not sure what is the purpose of this while loop? but if we break after reading  1 column
at a time, all works fine and cassandra starts up smoothly.

This looks similar to issue
https://issues.apache.org/jira/browse/CASSANDRA-1073

Jignesh

> Cassandra throws Exceptions at startup when using TTL in SuperColumns
> ---------------------------------------------------------------------
>
>                 Key: CASSANDRA-1130
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-1130
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Core
>    Affects Versions: 0.7
>            Reporter: Jignesh Dhruv
>            Assignee: Sylvain Lebresne
>             Fix For: 0.7
>
>
> Hello,
> I am trying to use TTL (timeToLive) feature in SuperColumns.
> My usecase is:
> - I have a SuperColumn and 3 subcolumns.
> - I try to expire data after 60 seconds.
> While Cassandra is up and running, I am successfully able to push and read data without
any problems. Data compaction and all occurs fine. After inserting say about 100000 records,
I stop Cassandra while data is still coming.
> On startup Cassandra throws an exception and won't start up. (This happens 1 in every
3 times). Exception varies like:
> - EOFException while reading data
> - negative value encountered exception
> - Heap Space Exception
> Cassandra simply won't start up.
> Again I get this problem only when I use TTL with SuperColumns. There are no issues with
using TTL with regular Columns.
> I tried to diagnose the problem and it seems to happen on startup when it sees a Column
that is marked Deleted and its trying to read data. Its off by some bytes and hence all these
exceptions.
> Caused by: java.io.IOException: Corrupt (negative) value length encountered
>         at org.apache.cassandra.utils.FBUtilities.readByteArray(FBUtilities.java:317)
>         at org.apache.cassandra.db.ColumnSerializer.deserialize(ColumnSerializer.java:84)
>         at org.apache.cassandra.db.SuperColumnSerializer.deserialize(SuperColumn.java:336)
>         at org.apache.cassandra.db.SuperColumnSerializer.deserialize(SuperColumn.java:285)
>         at org.apache.cassandra.db.filter.SSTableSliceIterator$ColumnGroupReader.getNextBlock(SSTableSliceIterator.java:235)
>         at org.apache.cassandra.db.filter.SSTableSliceIterator$ColumnGroupReader.pollColumn(SSTableSliceIterator.java:195)
>         ... 18 more
> Let me know if you need more information.
> Thanks,
> Jignesh

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