Uploaded image for project: 'Core Server'
  1. Core Server
  2. SERVER-27067

Some Commands do not wait for write concern for no-op writes

    XMLWordPrintableJSON

Details

    • Fully Compatible
    • ALL
    • v3.4, v3.2
    • Repl 2017-01-23, Repl 2017-02-13, Repl 2017-04-17, Repl 2017-05-08, Repl 2017-05-29, Repl 2017-07-31
    • 0

    Description

      The wait for write concern code returns early if the ReplClientInfo is not set:

      https://github.com/mongodb/mongo/blob/r3.4.0-rc3/src/mongo/db/write_concern.cpp#L223-L226

      This means that if certain commands that does write actually ends up as no-op, it will actually not end up waiting for write concern.

      Example case:

      1. Client sends drop command to mongos.
      2. Drop command times out waiting for write concern at mongod.
      3. Mongos retries command since write concern timeout is a retriable error with Shard::RetryPolicy::kIdempotent.
      4. Mongos retries drop command to mongod.
      5. Since collection is already dropped, it will get "ns does not exist" error.
      6. If the mongos used a new connection, it will not wait for replication at all because it does not have any client opTime set. However, if the same connection is used, it will wait for the write concern as expected.

      Some of the commands already wait for write concern correctly even though it ends up doing a no-op write via repl::ReplClientInfo::setLastOpToSystemLastOpTime (for example, findAndModify, write commands, applyOps, etc).

      Attachments

        Issue Links

          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-35387 Ensure retried commitTransaction command waits for writeConcern

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-25765 Commands should wait for write concern even if they throw an exception

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-30648 Set GlobalLockAcquisitionTracker after we waitForLock

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-33475 Retried findAndModify doesn't properly wait for writeConcern

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-33727 Do not wait for write concern if opTime didn't change during write

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-40965 createIndexes should set the latest optime on its opCtx to meet writeConcern if no indexes are found to need building

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

          Activity

            People

              judah.schvimer@mongodb.com Judah Schvimer
              randolph@mongodb.com Randolph Tan
              Votes:
              0 Vote for this issue
              Watchers:
              7 Start watching this issue

              Dates

                Created:
                Updated:
                Resolved: