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POШnconsistent counter values between replicas in Cassandra
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copied!<p>I've got a 3 machine Cassandra cluster using rack unaware placements strategy with a replication factor of 2. </p> <p>The column family is defined as follows:</p> <pre><code>create column family UserGeneralStats with comparator = UTF8Type and default_validation_class = CounterColumnType; </code></pre> <p>Unfortunately after a few days of production use I got some inconsistent values for the counters:</p> <p>Query on replica 1:</p> <pre><code>[default@StatsKeyspace] list UserGeneralStats['5261666978': '5261666978']; Using default limit of 100 ------------------- RowKey: 5261666978 => (counter=bandwidth, value=96545030198) => (counter=downloads, value=1013) => (counter=previews, value=10304) </code></pre> <p>Query on replica 2:</p> <pre><code>[default@StatsKeyspace] list UserGeneralStats['5261666978': '5261666978']; Using default limit of 100 ------------------- RowKey: 5261666978 => (counter=bandwidth, value=9140386229) => (counter=downloads, value=339) => (counter=previews, value=1321) </code></pre> <p>As the standard read repair mechanism doesn't seem to repair the values I tried to force an anti-entropy repair using nodetool repair. It did't have any effect on the counter values. </p> <p>Data inspection showed that the lower values for the counters are the correct ones so I suspect that either Cassandra (or Hector which I used as API to call Cassandra from Java) retried some increments. </p> <p>Any ideas how to repair the data and possibly prevent the sittuation from happening again?</p>

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