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https://issues.apache.org/jira/browse/NIFI-1582?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15726832#comment-15726832
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ASF subversion and git services commented on NIFI-1582:
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Commit e36b37692c528b2e9774f9f49737eb2d1a05960f in nifi's branch
refs/heads/master from [~JPercivall]
[ https://git-wip-us.apache.org/repos/asf?p=nifi.git;h=e36b376 ]
NIFI-1582 added state to UpdateAttribute as well as updated a few parts that
hadn't be touched in years (referenced the 'FlowFileMetadataEnhancer'
processor'. Also added a 'NUMBER_VALIDATOR' to StandardValidators
NIFI-1582 removing the option to use cluster state
NIFI-1582 addressing Oleg's comments
NIFI-1582 No longer forcing numbers as the init value and adding
getStateValue() to EL instead of using 'ATTRIBUTE_state'
NIFI-1582 Removing init state value
NIFI-1582 Adding documentation for the changes to Init State value
This closes #319
> New processor to update attributes with state
> ---------------------------------------------
>
> Key: NIFI-1582
> URL: https://issues.apache.org/jira/browse/NIFI-1582
> Project: Apache NiFi
> Issue Type: New Feature
> Reporter: Joseph Percivall
> Assignee: Joseph Percivall
> Fix For: 1.2.0
>
>
> This idea was sparked by a thread on the user list and should allow basic
> data science:
> I expect that in the future I’ll need something a little more sophisticated
> but for now my problem is very simple:
> I want to be able to trigger an alert (only once) when an attribute in an
> incoming stream, for instance, goes over a predefined threshold. The
> Processor should then trigger (only once again) another trigger when the
> signal goes back to normal (below threshold). Basically a RouteByAttribute
> but with memory.
> Thanks
> Claudio
> ------------------------------------------------
> Hello Claudio,
> Your use-case actually could leverage a couple of recently added features to
> create a really cool open-source processor. The two key features that were
> added are State Management and the ability to reference processor specific
> variables in expression language. You can take a look at RouteText to see
> both in action.
> By utilizing both you can create a processor that is configured with multiple
> Expression language expressions. There would be dynamic properties which
> would accept expression language and then store the evaluated value via state
> management. Then there would be a routing property (that supports expression
> language) that could simply add an attribute to the flowfile with the
> evaluated value which would allow it to be used by flowing processors for
> routing.
> This would allow you to do your use-case where you store the value for the
> incoming stream and route differently once you go over a threshold. It could
> even allow more complex use-cases. One instance, I believe, would be possible
> is to have a running average and standard deviation and route data to
> different locations based on it's standard deviation.
> You can think of this like an UpdateAttribute with the ability to store and
> calculate variables using expression language.
> Joe
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