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https://issues.apache.org/jira/browse/NIFI-190?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16170985#comment-16170985
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Koji Kawamura commented on NIFI-190:
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Hi [~Minmin_Sydney],
If I understand your use-case correctly, following approach might work:
Requirements:
# FF(D) waits for FF(A) and FF(B)
# FF(E) waits for FF(B) and FF(C)
Solution sammary:
Use two different Signal Identifier for FF(D) and FF(E), e.g. Signal(D) and
Signal(E).
Flow (I assume you have control which FlowFile go through which route):
# FF(D) --> Wait: Signal(D), "Target Signal Count" = 2, "Signal Counter Name" =
blank (so that it uses the total count, i.e: wait for A + B = 2)
# FF(E) --> Wait: Signal(E), "Target Signal Count" = 2, "Signal Counter Name" =
blank (so that it uses the total count, i.e: wait for B + C = 2)
# FF(A) --> Notify: Signal(D), "Signal Counter Name" = "A"
# FF(C) --> Notify: Signal(E), "Signal Counter Name" = "C"
# FF(B) --> Notify: Signal(D), "Signal Counter Name" = "B" --> Notify:
Signal(E), "Signal Counter Name" = "B". Important to use two different Notify
processors to increment counter for Signal(D) and Signal(E) here.
How do you think?
> 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 set of processors 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
> Notify will optionally cache attributes in the distributed map, as determined
> by a regex property. This is what allows the output of Endpoint A to pass to
> Endpoint B, above. Wait also allows conflicting attributes from the cache to
> either be replaced or kept, depending on property configuration.
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