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https://issues.apache.org/jira/browse/STORM-1187?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15010117#comment-15010117
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冯健 commented on STORM-1187:
---------------------------
In this paper
(http://www.cs.cmu.edu/~pavlo/courses/fall2013/static/papers/p734-akidau.pdf)
from google which describes a framework for building realtime computation
application,they provide a semantic named "Low Watermarks" which indicates that
all data up to a given timestamp(generation time) has been received. Using this
semantic,we can distinguish whether the events are simply delayed or actually
not there, also, out-of-order events won't be a problem anymore.
> Support for late and out of order events in time based windows
> --------------------------------------------------------------
>
> Key: STORM-1187
> URL: https://issues.apache.org/jira/browse/STORM-1187
> Project: Apache Storm
> Issue Type: Sub-task
> Reporter: Arun Mahadevan
> Assignee: Arun Mahadevan
>
> Right now the time based windows uses the timestamp when the tuple is
> received by the bolt.
> However there are use cases where the tuples can be processed based on the
> time when they are actually generated vs the time when they are received. So
> we need to add support for processing events with a time lag and also have
> some way to specify and read tuple timestamps.
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