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  1. Cassandra
  2. CASSANDRA-11427

Range slice queries CL > ONE trigger read-repair of purgeable tombstones

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    Details

    • Type: Bug
    • Status: Resolved
    • Priority: Low
    • Resolution: Fixed
    • Fix Version/s: 2.2.6
    • Component/s: None
    • Labels:
      None
    • Severity:
      Low

      Description

      Range queries will trigger read repairs for purgeable tombstones on hosts that already compacted given tombstones. Clusters with periodical jobs for scanning data ranges will likely see tombstones ressurected through RRs just to have them compacted again later at the destination host.

      Executing range queries (e.g. for reading token ranges) will compare the actual data instead of using digests when executed with CL > ONE. Responses will be consolidated by RangeSliceResponseResolver.Reducer, where the result of RowDataResolver.resolveSuperset is used as the reference version for the results. RowDataResolver.scheduleRepairs will then send the superset to all nodes that returned a different result before.

      Unfortunately this does also involve cases where the superset is just made up of purgeable tombstone(s) that already have been compacted on the other nodes. In this case a read-repair will be triggered for transfering the purgeable tombstones to all other nodes nodes that returned an empty result.

      The issue can be reproduced with the provided dtest or manually using the following steps:

      create keyspace test1 with replication = { 'class' : 'SimpleStrategy', 'replication_factor' : 2 };
      use test1;
      create table test1 ( a text, b text, primary key(a, b) ) WITH compaction = {'class': 'SizeTieredCompactionStrategy', 'enabled': 'false'} AND dclocal_read_repair_chance = 0 AND gc_grace_seconds = 0;
      
      delete from test1 where a = 'a';
      
      ccm flush;
      ccm node2 compact;
      
      use test1;
      consistency all;
      tracing on;
      select * from test1;
      

        Attachments

        1. 11427-2.2_v2.patch
          2 kB
          Stefan Podkowinski
        2. 11427-2.1.patch
          5 kB
          Stefan Podkowinski

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              • Assignee:
                spodxx@gmail.com Stefan Podkowinski
                Reporter:
                spodxx@gmail.com Stefan Podkowinski
                Authors:
                Stefan Podkowinski
                Reviewers:
                Sylvain Lebresne
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                • Created:
                  Updated:
                  Resolved: