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https://issues.apache.org/jira/browse/NIP-3?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17910390#comment-17910390
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Joe Witt commented on NIP-3:
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Good scenario to account for. Makes sense
> Allow components to be notified when cluster topology changes
> -------------------------------------------------------------
>
> Key: NIP-3
> URL: https://issues.apache.org/jira/browse/NIP-3
> Project: NiFi Improvement Proposal
> Issue Type: New Feature
> Reporter: Mark Payne
> Assignee: Mark Payne
> Priority: Minor
>
> The NiFi API provides several annotations that components can use to have
> code triggered or to be notified when things occur. A great example is the
> {{@OnPrimaryNodeChange}} annotation.
> We should provide the ability for components to be notified when the cluster
> topology changes. That is, when a node is added or removed from the cluster.
> This should not include when a node's state changes, for example from
> CONNECTED to DISCONNECTED or vice versa, but only when the nodes that make up
> the cluster change.
> The reasoning behind this is for cases in which data is load balanced across
> the cluster using an "Attribute Name." When the cluster topology changes, it
> is possible that data with attribute {{a=123}} will no longer go to Node 1
> but now go to Node 2. When this happens, Processors, Controller Services,
> etc. may need to be notified of this in order to cleanup resources. For
> example, a Processor may need to invalidate an internal cache data that
> corresponded to {{a=123}} may be outdated, since the data may have moved to
> another node and now back, etc.
> This will require adding a new annotation to the nifi-api that is scoped the
> same as {{@OnPrimaryNodeChange}} (i.e., it has a Target of METHOD, a
> Retention of RUNTIME, and is {{{}@Inherited{}}}). It will also require an
> update to the framework to call the methods when appropriate.
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