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  1. Core Server
  2. SERVER-39364

Audit uses of setLastOpToSystemLastOpTime

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Details

    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • 4.3.3
    • Replication
    • None
    • Fully Compatible
    • Repl 2019-12-30, Repl 2020-01-13, Repl 2020-01-27
    • 20

    Description

      It is not valid to call setLastOpToSystemLastOpTime() and then wait for majority writeConcern to ensure that any data read was majority committed. The reason is that writes update the lastApplied in an on-commit hook after the data changes are made. Consider the following scenario. Originally the lastApplied is time 1. Operation A updates the document {_id: 0} to have a=5 and writes an oplog entry with time 2. Operation B reads the document {_id: 0, a: 5}.  Operation B calls setLastOpToSystemLastOpTime() and gets the lastApplied time as time 1. Then the on-commit hook for Operation A updates the lastApplied to time 2. Operation B will wait for the majority commit point to reach time 1, which does not guarantee that the data that it read was majority committed.

      Any callers of setLastOpToSystemLastOpTime() that use it to ensure data read was majority committed are suspect. This excludes reading transaction state in transaction operations, since they are serialized by the session checkout mechanism, so a new transaction operation cannot start until the on-commit hooks have finished for the previous operation.

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          causes

          Bug - A problem which impairs or prevents the functions of the product. SERVER-45800 Unlock RSTL after calling setLastOpToSystemLastOpTime in PrepareTransactionCmd

          • Major - P3 - Major loss of function.
          • Closed
          depends on

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-43656 Return the timestamp of the top of the oplog in the storage integration layer

          • Major - P3 - Major loss of function.
          • Closed
          is depended on by

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-41165 Transaction participants don't need to do a noop write before committing a read-only transaction

          • Major - P3 - Major loss of function.
          • Backlog
          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-30217 applyOps doesn't wait for replication on the last op if it's a noop

          • Major - P3 - Major loss of function.
          • Backlog

          Bug - A problem which impairs or prevents the functions of the product. SERVER-37948 Linearizable read concern is not satisfied by getMores on a cursor

          • Major - P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. SERVER-39356 Change stream updateLookup queries with speculative majority may return uncommitted data

          • Major - P3 - Major loss of function.
          • Closed

          Task - A task that needs to be done. SERVER-38906 Multi-document transactions should not perform timestamped read ahead of all-committed

          • Major - P3 - Major loss of function.
          • Closed
          related to

          Task - A task that needs to be done. SERVER-45598 Complete TODO listed in SERVER-39364

          • Major - P3 - Major loss of function.
          • Closed

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-44820 bgSync grabs DBLock in X mode when reading the oplog

          • Major - P3 - Major loss of function.
          • Closed

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            People

              lingzhi.deng@mongodb.com Lingzhi Deng
              tess.avitabile@mongodb.com Tess Avitabile (Inactive)
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              Dates

                Created:
                Updated:
                Resolved: