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From Soumava Ghosh <soum...@cs.utexas.edu>
Subject Re: Cassandra 2.0 - AssertionError in ArrayBackedSortedColumns
Date Mon, 22 Jul 2013 07:24:48 GMT
Thanks for the reply Sylvain! A couple of follow-up questions:

i. The second stack in my mail originated at a getRow() call. What could be
the cause of that? I am assuming data retrieval should not cause any
issues, unless data was stored in incorrect order and I don't know if that
is possible through the API..

ii. I am also seeing some sporadic cases where a single column cas() update
is hitting this same issue (the bug you mentioned) as multiple columns, do
you see any reason for that happening? I am yet to investigate this though.

Thank you,
Soumava


On Mon, Jul 22, 2013 at 12:11 AM, Sylvain Lebresne <sylvain@datastax.com>wrote:

> This is a bug really: https://issues.apache.org/jira/browse/CASSANDRA-5786
> .
>
> This should get fixed in the next beta of 2.0, but if you really want to
> test CAS updates in the meantime, you'll have to provide the columns in
> (column family comparator) sorted order to the thrift cas() method.
>
> --
> Sylvain
>
>
> On Sun, Jul 21, 2013 at 1:22 PM, Soumava Ghosh <soumava@cs.utexas.edu>wrote:
>
>> Hi,
>>
>> I'm taking a look at the Check and Set functionalities provided by the
>> cas() API provided by cassandra 2.0 (the code available on git). I'm
>> running a few tests on a small sized cluster (replication factor 3,
>> consistency level quorum) with a few clients. I've observed a lot of cases
>> seem to hit the TimedOutException while paxos is in progress. On inspection
>> of the server side logs the following stack was seen:
>>
>> ERROR [Thread-582] 2013-07-21 01:17:46,169 CassandraDaemon.java (line
>> 196) Exception in thread Thread[Thread-582,5,main]
>> java.lang.AssertionError: Added column does not sort as the last column
>>         at
>> org.apache.cassandra.db.ArrayBackedSortedColumns.addColumn(ArrayBackedSortedColumns.java:115)
>>         at
>> org.apache.cassandra.db.ColumnFamily.addColumn(ColumnFamily.java:117)
>>         at
>> org.apache.cassandra.db.ColumnFamilySerializer.deserialize(ColumnFamilySerializer.java:119)
>>         at
>> org.apache.cassandra.db.ColumnFamilySerializer.deserialize(ColumnFamilySerializer.java:96)
>>         at
>> org.apache.cassandra.db.ColumnFamilySerializer.deserialize(ColumnFamilySerializer.java:91)
>>         at
>> org.apache.cassandra.service.paxos.Commit$CommitSerializer.deserialize(Commit.java:139)
>>         at
>> org.apache.cassandra.service.paxos.Commit$CommitSerializer.deserialize(Commit.java:128)
>>         at org.apache.cassandra.net.MessageIn.read(MessageIn.java:99)
>>         at
>> org.apache.cassandra.net.IncomingTcpConnection.receiveMessage(IncomingTcpConnection.java:175)
>>         at
>> org.apache.cassandra.net.IncomingTcpConnection.handleModernVersion(IncomingTcpConnection.java:135)
>>         at
>> org.apache.cassandra.net.IncomingTcpConnection.run(IncomingTcpConnection.java:82)
>>
>> I was updating multiple columns using the same cas() call, and looking at
>> the assert (code below) I added code to sort them before sending.
>> However, now I'm seeing the same issue *even with single column* cas()
>> calls.
>>
>>         int c = internalComparator().compare(columns.get(getColumnCount()
>> - 1).name(), column.name());
>>         // note that we want an assertion here (see addColumn javadoc),
>> but we also want that if
>>         // assertion are disabled, addColumn works correctly with
>> unsorted input
>>         assert c <= 0 : "Added column does not sort as the " + (reversed
>> ? "first" : "last") + " column";
>>
>> I have also seen this error occur in the getRow() path, as below:
>>
>> java.lang.AssertionError: Added column does not sort as the last column
>>         at
>> org.apache.cassandra.db.ArrayBackedSortedColumns.addColumn(ArrayBackedSortedColumns.java:115)
>>         at
>> org.apache.cassandra.db.ColumnFamily.addColumn(ColumnFamily.java:117)
>>         at
>> org.apache.cassandra.db.ColumnFamily.addAtom(ColumnFamily.java:151)
>>         at
>> org.apache.cassandra.db.CollationController.collectTimeOrderedData(CollationController.java:95)
>>         at
>> org.apache.cassandra.db.CollationController.getTopLevelColumns(CollationController.java:57)
>>         at
>> org.apache.cassandra.db.ColumnFamilyStore.getTopLevelColumns(ColumnFamilyStore.java:1452)
>>         at
>> org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1281)
>>         at
>> org.apache.cassandra.db.ColumnFamilyStore.getColumnFamily(ColumnFamilyStore.java:1195)
>>         at org.apache.cassandra.db.Table.getRow(Table.java:331)
>>         at
>> org.apache.cassandra.db.SliceByNamesReadCommand.getRow(SliceByNamesReadCommand.java:55)
>>         at
>> org.apache.cassandra.service.StorageProxy$LocalReadRunnable.runMayThrow(StorageProxy.java:1288)
>>         at
>> org.apache.cassandra.service.StorageProxy$DroppableRunnable.run(StorageProxy.java:1813)
>>         at
>> java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
>>         at
>> java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
>>         at java.lang.Thread.run(Thread.java:722)
>>
>> Could someone provide me a little more clarity about what the context of
>> the error is and what the client needs to do to fix it? I understand that
>> running with assertions disabled would do away with this error, but i'd
>> like to know if there is a proper way to fix this. Moreover, what could
>> possibly be going wrong in the get path that is hitting this issue?
>>
>> Some guidance, on the fact that whether it is expected that the client
>> sort the columns before calling the API with multiple columns, would be
>> really appreciated.
>>
>> Thanks,
>> Soumava
>>
>
>

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