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  1. Core Server
  2. SERVER-13806

Need better detection and reporting of the existence of jumbo chunks

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Won't Fix
    • Affects Version/s: None
    • Fix Version/s: None
    • Component/s: Sharding
    • Labels:
      None
    • Operating System:
      ALL
    • Steps To Reproduce:
      Hide

      sh.enableSharding("test");
      sh.shardCollection("test.foo",{a:1});
      sh.splitAt("test.foo",{a:1000});
      for (var i=0; i<10000000; i++) {db.getSiblingDB("test").foo.insert({a:1, padding:"xxxxxxxx...xxxxx"})}

      Run the above commands and observe that chunk MinKey -> 1000 is not marked as jumbo in the chunk meta data, even after it has grown past the max chunk size for the cluster.

      Show
      sh.enableSharding("test"); sh.shardCollection("test.foo",{a:1}); sh.splitAt("test.foo",{a:1000}); for (var i=0; i<10000000; i++) {db.getSiblingDB("test").foo.insert({a:1, padding:"xxxxxxxx...xxxxx"})} Run the above commands and observe that chunk MinKey -> 1000 is not marked as jumbo in the chunk meta data, even after it has grown past the max chunk size for the cluster.

      Description

      As far as I can see, a jumbo chunk is only marked as such when the balancer has attempted to migrate it to another shard (Chunk::markAsJumbo is only called from Balancer::_moveChunks).

      This means that there's no indication of jumbo chunks unless:

      • chunk imbalance has grown past the threshold at which the balancer tries to move chunks, and
      • the balancer has attempted to move a jumbo chunk to redress the imbalance

      It would be good to have more comprehensive and early warning of jumbo chunks. This checking could perhaps be added to the splitVector handling in mongod.

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                • Created:
                  Updated:
                  Resolved: