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  1. Documentation
  2. DOCS-14047

Investigate changes in SERVER-51333: setFeatureCompatibilityVersion should fail when downgrading from FCV 4.4 to FCV 4.2 with long collection names present


      Downstream Change Summary

      Setting FCV to 4.4 to 4.2 will now fail if long collection names (> 120chars) are present

      Description of Linked Ticket

      DatabaseImpl::_checkCanCreateCollection() throws an exception if a collection with a name longer than 120 characters is attempted to be created while in FCV 4.2. However, a node undergoing initial sync will also call that function and (depending on whether the admin.system.version collection has already been cloned) would fail its initial sync attempt and eventually exhaust its retries.

      [js_test:repro_initial_sync_long_collection_name] 2020-10-02T18:19:19.708+0000 d20021| {"t":{"$date":"2020-10-02T18:19:19.708+00:00"},"s":"E",  "c":"REPL",     "id":21416,   "ctx":"ReplCoordExtern-0","msg":"Initial sync failed, shutting down now. Restart the server to attempt a new initial sync"}
      [js_test:repro_initial_sync_long_collection_name] 2020-10-02T18:19:19.708+0000 d20021| {"t":{"$date":"2020-10-02T18:19:19.708+00:00"},"s":"F",  "c":"-",        "id":23095,   "ctx":"ReplCoordExtern-0","msg":"Fatal assertion","attr":{"msgid":40088,"error":"InitialSyncFailure: error cloning databases :: caused by :: IncompatibleServerVersion: Error cloning collection 'test.long_collection_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx' :: caused by :: Fully qualified namespace is too long for FCV 4.2. Upgrade to FCV 4.4 to create this namespace. Namespace: test.long_collection_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx FCV 4.2 Limit: 120","file":"src/mongo/db/repl/replication_coordinator_impl.cpp","line":754}}

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            Unassigned Unassigned
            backlog-server-pm Backlog - Core Eng Program Management Team
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              1 year, 29 weeks, 2 days ago