Operational Defect Database

BugZero found this defect 2360 days ago.

MongoDB | 425910

[SERVER-31019] Changing fCV during initial sync leads to divergent data across replica set members

Last update date:


Affected products:

MongoDB Server

Affected releases:

No affected releases provided.

Fixed releases:




The node performing the initial sync appears to be able to retain the documents that were inserted prior to the collection being dropped and re-created after changing the featureCompatibilityVersion to 3.6. This issue is related to UUIDs and their impact on oplog application, and therefore doesn't affect the 3.2 or 3.4 branches. 2017-09-10T19:21:06.495-0400 The following documents are missing on the primary: 2017-09-10T19:21:06.495-0400 { "_id" : "while in fCV=3.4" } ... 2017-09-10T19:21:06.498-0400 checkReplicatedDataHashes, the primary and secondary have a different hash for the test database: { 2017-09-10T19:21:06.498-0400 "master" : { 2017-09-10T19:21:06.499-0400 "host" : "hanamizu:20010", 2017-09-10T19:21:06.499-0400 "collections" : { 2017-09-10T19:21:06.499-0400 "mycoll" : "09aabf5621c57d91db16b98b365d8e65" 2017-09-10T19:21:06.499-0400 }, 2017-09-10T19:21:06.499-0400 "md5" : "2105eeb0b1ec2ade59f08fa1f3f40ba9", 2017-09-10T19:21:06.499-0400 "timeMillis" : 0, 2017-09-10T19:21:06.499-0400 "ok" : 1, 2017-09-10T19:21:06.499-0400 "operationTime" : Timestamp(1505085665, 18) 2017-09-10T19:21:06.499-0400 }, 2017-09-10T19:21:06.499-0400 "slaves" : [ 2017-09-10T19:21:06.499-0400 { 2017-09-10T19:21:06.500-0400 "host" : "hanamizu:20011", 2017-09-10T19:21:06.500-0400 "collections" : { 2017-09-10T19:21:06.500-0400 "mycoll" : "b8b6211fb0b559d95ae6df5cc4071420" 2017-09-10T19:21:06.500-0400 }, 2017-09-10T19:21:06.500-0400 "md5" : "072bbaef3649d98b3270e6a2a6eac21f", 2017-09-10T19:21:06.500-0400 "timeMillis" : 0, 2017-09-10T19:21:06.500-0400 "ok" : 1, 2017-09-10T19:21:06.500-0400 "operationTime" : Timestamp(1505085665, 18) 2017-09-10T19:21:06.500-0400 } 2017-09-10T19:21:06.500-0400 ] 2017-09-10T19:21:06.500-0400 }

Top User Comments

xgen-internal-githook commented on Mon, 9 Oct 2017 15:20:08 +0000: Author: {'email': 'judah@mongodb.com', 'name': 'Judah Schvimer', 'username': 'judahschvimer'} Message: SERVER-31019 fail initial sync if fCV changes during oplog application Branch: master https://github.com/mongodb/mongo/commit/d7a30a716243db13644a16618a939df6bc1344fc spencer commented on Fri, 15 Sep 2017 16:22:06 +0000: To fix this we should just fail initial sync if the featureCompatibilityVersion changes in the middle of it. To do this, we should make sure that the very first collection we clone is admin.system.version, so that we know the FCV of the sync source at the beginning of initial sync. Then during initial sync oplog application, we should fail and restart initial sync if we replicate a change to the FCV.

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