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  1. Core Server
  2. SERVER-14323

Balancer hits config servers hard even though there are no writes

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 2.6.3, 3.0.12, 3.2.8, 3.3.8
    • Fix Version/s: 3.3.9
    • Component/s: Sharding
    • Labels:
    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Steps To Reproduce:
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      In my case, I have a database in 2 shards with slightly less than 30M documents in about 130k chunks. I have 6 mongos instances and, each reading from the first config server at about 20 mbit/s which is 120mbit/s in total. I have to control the balancer manually due to this.

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      In my case, I have a database in 2 shards with slightly less than 30M documents in about 130k chunks. I have 6 mongos instances and, each reading from the first config server at about 20 mbit/s which is 120mbit/s in total. I have to control the balancer manually due to this.

      Description

      Every mongos instance starts a balancer round every few seconds. While looking for candidate chunks to move, it always reads all of the chunks with the given ns from the config database, many times only to realize that the collection is in fact well balanced. This may cause a significant network load.

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                  Updated:
                  Resolved: