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  1. Cassandra
  2. CASSANDRA-12730

Thousands of empty SSTables created during repair - TMOF death



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      Last night I ran a repair on a keyspace with 7 tables and 4 MVs each containing a few hundret million records. After a few hours a node died because of "too many open files".
      Normally one would just raise the limit, but: We already set this to 100k. The problem was that the repair created roughly over 100k SSTables for a certain MV. The strange thing is that these SSTables had almost no data (like 53bytes, 90bytes, ...). Some of them (<5%) had a few 100 KB, very few (<1% had normal sizes like >= few MB). I could understand, that SSTables queue up as they are flushed and not compacted in time but then they should have at least a few MB (depending on config and avail mem), right?
      Of course then the node runs out of FDs and I guess it is not a good idea to raise the limit even higher as I expect that this would just create even more empty SSTables before dying at last.

      Only 1 CF (MV) was affected. All other CFs (also MVs) behave sanely. Empty SSTables have been created equally over time. 100-150 every minute. Among the empty SSTables there are also Tables that look normal like having few MBs.
      I didn't see any errors or exceptions in the logs until TMOF occured. Just tons of streams due to the repair (which I actually run over cs-reaper as subrange, full repairs).
      After having restarted that node (and no more repair running), the number of SSTables went down again as they are compacted away slowly.

      According to Nate McCall this issue may relate to CASSANDRA-10342 + CASSANDRA-8641


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              • Assignee:
                brstgt Benjamin Roth
                brstgt Benjamin Roth
                Benjamin Roth
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