[jira] [Resolved] (NIFI-12386) Add a FilterAttribute processor

["Michael W Moser (Jira)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/NIFI-12386?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Michael W Moser resolved NIFI-12386.
------------------------------------
    Fix Version/s: 1.25.0
                   2.0.0
       Resolution: Implemented

> Add a FilterAttribute processor
> -------------------------------
>
>                 Key: NIFI-12386
>                 URL: https://issues.apache.org/jira/browse/NIFI-12386
>             Project: Apache NiFi
>          Issue Type: New Feature
>          Components: Core Framework
>            Reporter: endzeit
>            Assignee: endzeit
>            Priority: Major
>             Fix For: 1.25.0, 2.0.0
>
>          Time Spent: 15h
>  Remaining Estimate: 0h
>
> Flows in Apache NiFi can get quite sophisticated, consisting of a long chains of both {{ProcessGroup}} and {{Processor}} components.
> Oftentimes {{Processor}} components, including those in the NiFi standard bundle, enrich an incoming {{FlowFile}} with additional FlowFile attributes.
> This can lead to a fair amount of different FlowFile attributes accumulating over the FlowFile's lifecycle.
> In order to prevent subsequent {{ProcessGroup}} / {{Processor}} components to accidentally rely on implementation details of preceding components, a good practice is to:
>  # define which FlowFile attributes should exist at selected points in the {{Flow}}
>  # reduce the attributes of the FlowFile at the selected point to those defined
> This can be achieved by using the [UpdateAttribute|https://nifi.apache.org/docs/nifi-docs/components/org.apache.nifi/nifi-update-attribute-nar/1.23.2/org.apache.nifi.processors.attributes.UpdateAttribute/index.html] processor of the standard processor bundle.
> However, the {{UpdateAttribute}} processor allows only for a regular expression to define a set of attributes to remove. Instead, the outlined practice above desires to explicitly state a set of attributes to keep. One can do so with a regular expression as well, but writing the reverse lookup to achieve this is not the easiest endeavor to put it mildly.
> This issue proposes a new processor {{FilterAttribute}} to be added to the library of {{{}nifi-standard-processors{}}}, which can be configured with a set of attributes and removes all attributes of an incoming FlowFile other than the ones configured.
> The processor should
>  * have a required, non-blank property "Attributes to keep", which takes a list of attribute names separated by delimiter, e.g. comma (,).
>  ** trailing whitespace around attribute names should be ignored
>  ** leading or trailing delimiters should be ignored
>  * have a required, non-blank property "Delimiter", which is used to delimit the individual attribute names, with a default value of "," (comma).
>  * have a single relationship "success" to which all FlowFiles are routed, similar to {{UpdateAttribute}}
>  * have an [InputRequirement|https://www.javadoc.io/doc/org.apache.nifi/nifi-api/latest/org/apache/nifi/annotation/behavior/InputRequirement.html] of [INPUT_REQUIRED|https://www.javadoc.io/doc/org.apache.nifi/nifi-api/latest/org/apache/nifi/annotation/behavior/InputRequirement.Requirement.html]
>  * [@SupportsBatching|https://www.javadoc.io/doc/org.apache.nifi/nifi-api/latest/org/apache/nifi/annotation/behavior/SupportsBatching.html]
>  * be [@SideEffectFree|https://www.javadoc.io/doc/org.apache.nifi/nifi-api/latest/org/apache/nifi/annotation/behavior/SideEffectFree.html]
> Some possible extension might be:
>  * have a required property "Core attributes", with allowable values of "Keep UUID only", "Keep all", with a default of "Keep UUID only"
>  ** an additional allowable value e.g. "Specify behaviour" may be added, which allows for more customization
>  * have a required property "Mode", with allowable values of "Retain" and "Remove", with a default of "Retain"



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