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  1. Couchbase Server
  2. MB-33854

[6.0.2] - Memcached returns NOT_STORED to client after trying to perform arithmetic operation

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Details

    • Bug
    • Status: Closed
    • Major
    • Resolution: Fixed
    • 6.5.0, 5.5.0, 5.5.3, 6.0.1
    • 6.0.2
    • memcached
    • Untriaged
    • Yes

    Description

      [Cloned this from MB-33813 to track merging a fix for this issue to 6.0.2.]

      There is a race condition in ArithmeticCommandContext where a SET operation is performed between the ArithmeticCommandContext::getItem() and ArithmeticCommandContext::storeNewItem(), causing the call to bucket_store() to return ENGINE_NOT_STORED. Currently we just return this error to the memcached client however, this brakes the behaviour of this interface that existed before the refactoring of our arithmetic operations (see v4.5.0). Thus, we should resolve this race condition by trying to re-perform the arithmetic operation by resetting the ArithmeticCommandContext state machine.

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            wayne Wayne Siu created issue -
            wayne Wayne Siu made changes -
            Field Original Value New Value
            Description There is a race condition in {{ArithmeticCommandContext}} where a {{SET}} operation is performed between the {{ArithmeticCommandContext::getItem()}} and {{ArithmeticCommandContext::storeNewItem()}}, causing the call to {{bucket_store()}} to return {{ENGINE_NOT_STORED}}. Currently we just return this error to the memcached client however, this brakes the behaviour of this interface that existed before the refactoring of our arithmetic operations (see v4.5.0). Thus, we should resolve this race condition by trying to re-perform the arithmetic operation by resetting the {{ArithmeticCommandContext}} state machine.

            [Cloned this from MB-33813 to track merging a fix for this issue to 6.0.2.]

            There is a race condition in {{ArithmeticCommandContext}} where a {{SET}} operation is performed between the {{ArithmeticCommandContext::getItem()}} and {{ArithmeticCommandContext::storeNewItem()}}, causing the call to {{bucket_store()}} to return {{ENGINE_NOT_STORED}}. Currently we just return this error to the memcached client however, this brakes the behaviour of this interface that existed before the refactoring of our arithmetic operations (see v4.5.0). Thus, we should resolve this race condition by trying to re-perform the arithmetic operation by resetting the {{ArithmeticCommandContext}} state machine.

            wayne Wayne Siu made changes -
            Affects Version/s 6.0.1 [ 15522 ]
            Affects Version/s master [ 13407 ]
            wayne Wayne Siu made changes -
            Fix Version/s 6.0.2 [ 15919 ]
            Fix Version/s Mad-Hatter [ 15037 ]
            wayne Wayne Siu made changes -
            Link This issue is a backport of MB-33813 [ MB-33813 ]
            wayne Wayne Siu made changes -
            Link This issue blocks MB-32630 [ MB-32630 ]
            richard.demellow Richard deMellow made changes -
            Link This issue relates to CBSE-6638 [ CBSE-6638 ]
            richard.demellow Richard deMellow made changes -
            Resolution Fixed [ 1 ]
            Status Open [ 1 ] Resolved [ 5 ]
            richard.demellow Richard deMellow made changes -
            Actual End 2019-04-18 10:17 (issue has been resolved)
            ritam.sharma Ritam Sharma made changes -
            VERIFICATION STEPS Closing based on unit test attached with the defect.
            Status Resolved [ 5 ] Closed [ 6 ]

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              richard.demellow Richard deMellow
              richard.demellow Richard deMellow
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              Dates

                Created:
                Updated:
                Resolved:

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