Major - P3 While running patch with causal consistency set to true by default got this error
[js_test:commands_namespace_parsing] 2017-07-05T18:09:09.180+0000 assert: [40413] != [73] are not equal : Expected failure code did not match actual in command result: { [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.181+0000 "ok" : 0, [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.181+0000 "errmsg" : "BSON field 'OperationSessionInfo.$logicalTime' is a duplicate field", [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.181+0000 "code" : 40413, [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.181+0000 "codeName" : "Location40413", [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.181+0000 "$logicalTime" : { [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.182+0000 "clusterTime" : Timestamp(1499278149, 2), [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.182+0000 "signature" : { [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.182+0000 "hash" : BinData(0,"ih/XXAirsRLy+ar0M3Ut9wDmC7c="), [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.182+0000 "keyId" : NumberLong("6439350411403984900") [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.182+0000 } [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.183+0000 }, [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.183+0000 "operationTime" : Timestamp(1499278149, 2) [js_test:commands_namespace_parsing] 2017-07-05T18:09:09.183+0000 } : undefined
Investigated, testing the fix.
The code running the command on mongos propagates the response from mongod and adds cluster time without check: https://github.com/mongodb/mongo/blob/r3.5.9/src/mongo/s/commands/strategy.cpp#L133
This also happens when mongod sends the request to a another shard: https://github.com/mongodb/mongo/blob/r3.5.9/src/mongo/db/service_entry_point_mongod.cpp#L267
The proposed fix is to skip appending cluster time if its already there in https://github.com/mongodb/mongo/blob/r3.5.9/src/mongo/rpc/metadata/logical_time_metadata.cpp#L105. Will use the greatest of both cluster times