Fix the read race condition in CFStore for counters
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Key: CASSANDRA-2105
URL: https://issues.apache.org/jira/browse/CASSANDRA-2105
Project: Cassandra
Issue Type: Bug
Affects Versions: 0.8
Reporter: Sylvain Lebresne
Assignee: Sylvain Lebresne
Fix For: 0.8
There is a (known) race condition during counter read. Indeed, for standard
column family there is a small time during which a memtable is both active and
pending flush and similarly a small time during which a 'memtable' is both
pending flush and an active sstable. For counters that would imply sometime
reconciling twice during a read the same counterColumn and thus over-counting.
Current code changes this slightly by trading the possibility to count twice a
given counterColumn by the possibility to miss a counterColumn. Thus it trades
over-counts for under-counts.
But this is no fix and there is no hope to offer clients any kind of guarantee
on reads unless we fix this.
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