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  1. Documentation
  2. DOCS-2908

That we run READ_UNCOMMITTED should be documented

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    • Task
    • Status: Closed
    • Major - P3
    • Resolution: Fixed
    • None
    • v1.3.3
    • manual
    • None
    • 8
    • true

    Description

      We should update this page:

      http://docs.mongodb.org/manual/reference/write-concern/

      and this:

      http://docs.mongodb.org/manual/faq/fundamentals/#does-mongodb-support-acid-transactions

      to reflect the question posed here if the observed behavior is true:

      http://smalldatum.blogspot.com/2014/03/when-does-mongodb-make-transaction.html

      That is, if we consider the write fully committed only after it hits the journal, when j=true, then we should warn that another reader may see the write before it is fully committed. In the event of a failure and rollback, later readers may not see the write.

      This problem may also affect w=majority writes. In general, we want to guarantee the behavior that once a majority of members have seen the write, it is durable, even across the loss the primary. The problem is, if a majority of replica set nodes don't ack the write, and it's rolled back, someone on the primary may have already seen it.

      Essentially, we run READ_UNCOMMITTED. We should document this fact to avoid user confusion.

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            sam.kleinman Sam Kleinman (Inactive)
            erlichson Andrew Erlichson
            Jonathan Dahl Jonathan Dahl
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            Dates

              Created:
              Updated:
              Resolved:
              8 years, 13 weeks, 6 days ago