Amanda Debrot created CASSANDRA-13153:
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Summary: Reappeared Data when Mixing Incremental and Full Repairs
Key: CASSANDRA-13153
URL: https://issues.apache.org/jira/browse/CASSANDRA-13153
Project: Cassandra
Issue Type: Bug
Components: Compaction, Tools
Environment: Apache Cassandra 2.2
Reporter: Amanda Debrot
Attachments: log-Reappeared-Data.txt,
Step-by-Step-Simulate-Reappeared-Data.txt
This happens for both LeveledCompactionStrategy and
SizeTieredCompactionStrategy. I've only tested it on Cassandra version 2.2 but
it most likely also affects all Cassandra versions with incremental repair -
like 2.1 and 3.0.
When mixing incremental and full repairs, there are a few scenarios where the
Data SSTable is marked as unrepaired and the Tombstone SSTable is marked as
repaired. Then if it is past gc_grace, and the tombstone and data has been
compacted out on other replicas, the next incremental repair will push the Data
to other replicas without the tombstone.
Simplified scenario:
3 node cluster with RF=3
Intial config:
Node 1 has data and tombstone in separate SSTables.
Node 2 has data and no tombstone.
Node 3 has data and tombstone in separate SSTables.
Incremental repair (nodetool repair -pr) is run every day so now we have
tombstone on each node.
Some minor compactions have happened since so data and tombstone get merged to
1 SSTable on Nodes 1 and 3.
Node 1 had a minor compaction that merged data with tombstone. 1
SSTable with tombstone.
Node 2 has data and tombstone in separate SSTables.
Node 3 had a minor compaction that merged data with tombstone. 1
SSTable with tombstone.
Incremental repairs keep running every day.
Full repairs run weekly (nodetool repair -full -pr).
Now there are 2 scenarios where the Data SSTable will get marked as
"Unrepaired" while Tombstone SSTable will get marked as "Repaired".
Scenario 1:
Since the Data and Tombstone SSTable have been marked as "Repaired" and
anticompacted, they have had minor compactions with other SSTables containing
keys from other ranges. During full repair, if the last node to run it doesn't
own this particular key in it's partitioner range, the Data and Tombstone
SSTable will get anticompacted and marked as "Unrepaired". Now in the next
incremental repair, if the Data SSTable is involved in a minor compaction
during the repair but the Tombstone SSTable is not, the resulting compacted
SSTable will be marked "Unrepaired" and Tombstone SSTable is marked "Repaired".
Scenario 2:
Only the Data SSTable had minor compaction with other SSTables
containing keys from other ranges after being marked as "Repaired". The
Tombstone SSTable was never involved in a minor compaction so therefore all
keys in that SSTable belong to 1 particular partitioner range. During full
repair, if the last node to run it doesn't own this particular key in it's
partitioner range, the Data SSTable will get anticompacted and marked as
"Unrepaired". The Tombstone SSTable stays marked as Repaired.
Then it’s past gc_grace. Since Node’s #1 and #3 only have 1 SSTable for that
key, the tombstone will get compacted out.
Node 1 has nothing.
Node 2 has data (in unrepaired SSTable) and tombstone (in repaired
SSTable) in separate SSTables and levels.
Node 3 has nothing.
Now when the next incremental repair runs, it will only use the Data SSTable to
build the merkle tree since the tombstone SSTable is flagged as repaired and
data SSTable is marked as unrepaired. And the data will get repaired against
the other two nodes.
Node 1 has data.
Node 2 has data and tombstone in separate SSTables and levels.
Node 3 has data.
If a read request hits Node 1 and 3, it will return data. If it hits 1 and 2,
or 2 and 3, however, it would return no data.
Tested this with single range tokens for simplicity.
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