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Type: Bug
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Resolution: Done
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Priority: Major - P3
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Affects Version/s: 3.2.0-rc0
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Component/s: Replication
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Labels:None
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Fully Compatible
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ALL
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Repl B (10/30/15), Repl C (11/20/15), Repl D (12/11/15)
In order to support readConcern, 3.2 nodes log an n-op to the oplog, effectively creating a floor for what they will consider committed. 3.0 nodes ignore n-ops while processing the oplog. This can cause a problem wherein no node believes themselves to be electable:
- 3.2 low priority node is elected and logs an n-op
- that node steps down from primary due to a heartbeat from a higher priority node
- that higher priority node (3.0) will not run because it is not the freshest
- the 3.2 node will not run because it is not highest priority
Log containing example for mixed_storage_version_replication.js: https://logkeeper.mongodb.org/build/56295972be07c42d836c7ac3/test/5629599abe07c42d836c7ec7?raw=1