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  1. Core Server
  2. SERVER-86474

$_internalApplyOplogUpdate with $set: { foo: Timestamp(0, 0) } is not replicated correctly

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    • Query Execution
    • Fully Compatible
    • ALL
    • v7.3, v7.0, v6.0, v5.0
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      launch a 3-node replica set.

      On the primary:

      > use test
> db.coll.insertOne({_id: 1})
> db.runCommand({update: "coll", bypassDocumentValidation: true, ordered: true, stmtIds: [ 0 ], updates: [ { q: { _id: 1 }, u: [ { $_internalApplyOplogUpdate: { oplogUpdate: { $v: 1, $set: { foo: Timestamp(0, 0) } } } } ], multi: false, upsert: false, collation: { locale: "simple" } } ]})
> db.coll.findOne()

      The result is 

      { _id: 1, foo: Timestamp(\{ t: 0, i: 0 }

      ) } on the primary.

      On any secondary:

      > use test
> db.getMongo().setReadPref('secondary')
> db.coll.findOne()

      The result is something like

      { _id: 1, foo: Timestamp(\{ t: 1707506908, i: 2 }

      ) } on the secondary. The actual timestamp will be the current time.

      Show
      launch a 3-node replica set. On the primary: > use test > db.coll.insertOne({_id: 1}) > db.runCommand({update: "coll" , bypassDocumentValidation: true , ordered: true , stmtIds: [ 0 ], updates: [ { q: { _id: 1 }, u: [ { $_internalApplyOplogUpdate: { oplogUpdate: { $v: 1, $set: { foo: Timestamp(0, 0) } } } } ], multi: false , upsert: false , collation: { locale: "simple" } } ]}) > db.coll.findOne() The result is  { _id: 1, foo: Timestamp(\{ t: 0, i: 0 } ) } on the primary. On any secondary: > use test > db.getMongo().setReadPref( 'secondary' ) > db.coll.findOne() The result is something like { _id: 1, foo: Timestamp(\{ t: 1707506908, i: 2 } ) } on the secondary. The actual timestamp will be the current time.
    • QE 2024-03-18, QE 2024-04-01, Repl 2024-02-19

      Problem

      mongosync is running into a data consistency error in our internal testing when $_internalApplyOplogUpdate is used with $set: { foo: Timestamp(0, 0) }. The primary will set foo to Timestamp(0, 0). But secondaries will set foo to the current timestamp.

      Although $_internalApplyOplogUpdate is for internal use only and will likely not affect external users, mongosync may corrupt user data if $_internalApplyOplogUpdate is not replicated correctly.

      Solution & Acceptance Criteria

      • Fix the replication bug.
      • Figure out if this bug affects regular update command.
      • Figure out if this bug only affects Timestamp(0, 0)

      Impact

      mongosync will not corrupt user data.

      Optional Permalinks

      REP-4005 is where this bug was first discovered.

            Assignee:
            andrew.paroski@mongodb.com Drew Paroski
            Reporter:
            craven.huynh@mongodb.com Craven Huynh
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              Created:
              Updated:
              Resolved: