[jira] [Created] (CASSANDRA-10353) NULL in compaction_history in 2.2.1

["Tommy Stendahl (JIRA)" <ji...@apache.org>]

Tommy Stendahl created CASSANDRA-10353:
------------------------------------------

             Summary: NULL in compaction_history in 2.2.1
                 Key: CASSANDRA-10353
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-10353
             Project: Cassandra
          Issue Type: Bug
            Reporter: Tommy Stendahl


While doing some tests on 2.2.1 I found a problem with a null value in the compaction_history table that results in a nullpointer exception when doing 'nodetool compactionhistory'.

{quote}
$ ccm node1 nodetool compactionhistory
Compaction History:
error: null
-- StackTrace --
java.lang.NullPointerException
    at com.google.common.base.Joiner$MapJoiner.join(Joiner.java:330)
    at org.apache.cassandra.utils.FBUtilities.toString(FBUtilities.java:477)
    at org.apache.cassandra.db.compaction.CompactionHistoryTabularData.from(CompactionHistoryTabularData.java:78)
    at org.apache.cassandra.db.SystemKeyspace.getCompactionHistory(SystemKeyspace.java:425)
    at org.apache.cassandra.db.compaction.CompactionManager.getCompactionHistory(CompactionManager.java:1492)
{quote}

The problem is the null value in the rows_merged column.

{quote}
cqlsh> SELECT * FROM system.compaction_history ;

 id                                   | bytes_in | bytes_out | columnfamily_name       | compacted_at             | keyspace_name | rows_merged
--------------------------------------+----------+-----------+-------------------------+--------------------------+---------------+--------------------
 86548100-5adf-11e5-a4f4-29d398af617a |      366 |        64 | compactions_in_progress | 2015-09-14 12:52:58+0000 |        system |             \{2: 2}
 9ff24610-5adf-11e5-a4f4-29d398af617a |       30 |         0 |                     bar | 2015-09-14 12:53:41+0000 |           foo |               null
 e4ffb130-5ade-11e5-a4f4-29d398af617a |      366 |        64 | compactions_in_progress | 2015-09-14 12:48:27+0000 |        system |             \{2: 2}
{quote}

After some more testing and digging in the code I realised that this is the result of a compaction where all sstables are dropped (i.e. no new sstable is created).

I tried to recreate this using 2.1.9 and found that there where nothing inserted into the compaction_history table if the same thing happens. That is  due to a check in CompactionTask.runMayThrow() line 181.

{code}
if (!iter.hasNext())
{
    // don't mark compacted in the finally block, since if there _is_ nondeleted data,
    // we need to sync it (via closeAndOpen) first, so there is no period during which
    // a crash could cause data loss.
    cfs.markObsolete(sstables, compactionType);
    return;
}
{code}

The result of the return here is that we end the compaction without inserting anything in the compaction_history table, 2.2.1 does not have this logic and will insert the null value.

Not sure what the best solution would be:
1. Implement the same behaviour as in 2.1.9 and skip inserting anything into  compaction_history.
2. Make sure we insert a more sensible value then null, but I'm not sure what that value would be.
3. Have nodetool handle the null value without a nullpointer exception. 



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