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  1. Core Server
  2. SERVER-30899

Adapting meaning of 'fromRouter' causes problems in mixed version clusters

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    • Backwards Compatibility:
      Fully Compatible
    • Operating System:
      ALL
    • Sprint:
      Query 2017-09-11

      Description

      As part of the work for SERVER-18940 we changed 'fromRouter' to mean 'command came from mongos', instead of its previous meaning, which was 'output from this command is going to be merged with output from other shards'. For the latter case, we added another field, 'needsMerge'.

      In a 3.4/3.6 mixed version cluster, a 3.4 mongos will set 'fromRouter' when talking to a 3.6 node, which will not interpret that as meaning 'needsMerge'. This can cause problems like the 3.6 node failing to serialize metadata such as the sort key.

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              Assignee:
              tess.avitabile Tess Avitabile
              Reporter:
              charlie.swanson Charlie Swanson
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