Blocker - P1 We're seeing the following message throuout the mongodb.log
2017-12-15T19:30:00.066+0000 I SHARDING [ShardServerCatalogCacheLoader-288] Refresh for collection config.system.sessions took 8 ms and failed :: caused by :: CommandNotFound: no such command: '_flushRoutingTableCacheUpdates', bad cmd: '{ _flushRoutingTableCacheUpdates: "config.system.sessions", maxTimeMS: 30000, $clusterTime: { clusterTime: Timestamp(1513366200, 20), signature: { hash: BinData(0, 57A6116452ABC8C74CDBD7EEBA4479D043B448AB), keyId: 6494298054030525147 } }, $configServerState: { opTime: { ts: Timestamp(1513366187, 292), t: 28 } }, $db: "admin" }'
2017-12-15T19:30:00.066+0000 I CONTROL [thread24] Sessions collection is not set up; waiting until next sessions refresh interval: no such command: '_flushRoutingTableCacheUpdates', bad cmd: '{ _flushRoutingTableCacheUpdates: "config.system.sessions", maxTimeMS: 30000, $clusterTime: { clusterTime: Timestamp(1513366200, 20), signature: { hash: BinData(0, 57A6116452ABC8C74CDBD7EEBA4479D043B448AB), keyId: 6494298054030525147 } }, $configServerState: { opTime: { ts: Timestamp(1513366187, 292), t: 28 } }, $db: "admin" }'
This secondary node is running on 3.6.0-56-g1a81fbe, primary is on 3.6.0-rc8