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https://issues.apache.org/jira/browse/NIFI-190?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Joseph Gresock reassigned NIFI-190:
-----------------------------------

    Assignee: Joseph Gresock  (was: Bryan Bende)

> Wait/Notify processors
> ----------------------
>
>                 Key: NIFI-190
>                 URL: https://issues.apache.org/jira/browse/NIFI-190
>             Project: Apache NiFi
>          Issue Type: New Feature
>          Components: Extensions
>            Reporter: Joseph Gresock
>            Assignee: Joseph Gresock
>            Priority: Minor
>             Fix For: 1.2.0
>
>         Attachments: Wait_Notify_template.xml
>
>
> Our team has developed a processor for the following use case:
> * Format A needs to be sent to Endpoint A
> * Format B needs to be sent to Endpoint B, but should not proceed until A has 
> reached Endpoint A.  We most commonly have this restriction when Endpoint B 
> requires some output of Endpoint A.
> The proposed Wait/Notify processors enable this functionality:
> * Wait: routes files to the 'wait' relationship until a matching Release 
> Signal Identifier is found in the distributed map cache.  Then routes them to 
> 'success' (unless they have expired)
> * Notify: stores a Release Signal Identifier in the distributed map cache, 
> optionally with attributes to copy to the outgoing matching Wait flow files.
> An example:
> Wait is configured with Release Signal Attribute = "${myId}". Its 'wait' 
> relationship routes back onto itself.
>     flowFile 1 { myId : "123" }
>     comes into Wait processor
>     Wait checks the distributed cache map for "123", doesn't find it, and is 
> routed to the 'wait' relationship
> Notify is configured with Release Signal Attribute = "${myId}"
>     flowFile 2 { myId : "123" }
>     comes in to Notify processor
>     Notify puts an entry in the map for "123" with any other attributes from 
> flowFile2
> Next time flowFile 1 is processed by Wait...
>     Finds an entry for "123"
>     Removes that entry from the map
>     Copies attributes to flowFile 1
>     Sends flowFile 1 out the success relationship
> Signal flow files will also copy their attributes to matching held files, as 
> optionally configured by an attribute name regex property.  This is what 
> allows the output of Endpoint A to pass to Endpoint B, above.  Wait also 
> allows conflicting attributes to either be replaced or kept, depending on 
> property configuration.



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