GitHub user ernisv opened a pull request:

    https://github.com/apache/storm/pull/1888

    STORM-2296 Kafka spout no dup on leader changes 1 x

    Current behavior of Kafka spout emits duplicate tuples whenever Kafka topic 
leader's change.
    In case of exception caused by leader changes, PartitionManagers are simply 
recreated losing the state about which tuples were already emitted and new 
PartitionManager re-emits them again.
    
    This is fine as at-least-once is fulfilled, but still it would be better to 
not emit duplicate data if possible.
    Moreover this could be easily avoided by moving the state related to 
emitted tuples from old PartitionManager to new one.

You can merge this pull request into a Git repository by running:

    $ git pull https://github.com/ernisv/storm 
kafka_spout_no_dup_on_leader_changes_1_x

Alternatively you can review and apply these changes as the patch at:

    https://github.com/apache/storm/pull/1888.patch

To close this pull request, make a commit to your master/trunk branch
with (at least) the following in the commit message:

    This closes #1888
    
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commit fb9c3073f5babc35828abdcf897db31846cabecc
Author: Ernestas Vaiciukevicius <e.vaiciukevic...@adform.com>
Date:   2017-01-12T14:54:59Z

    Move state from old PartitionManager when recreating manager for same 
partition

commit aefd80a5404b726d1dd538018b4f7f0bca119627
Author: Ernestas Vaiciukevicius <e.vaiciukevic...@adform.com>
Date:   2017-01-12T15:39:51Z

    Test to check if old PartitionManager's state is moved to new manager 
during manager recreate

commit c744e4b7dcbca5082243a691d97f12cd4b1151c3
Author: Ernestas Vaiciukevicius <e.vaiciukevic...@adform.com>
Date:   2017-01-12T15:57:46Z

    Include _emittedToOffset when copying state during PartitionManager recreate

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