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https://issues.apache.org/jira/browse/NIP-22?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18066036#comment-18066036
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Isha Lamboo commented on NIP-22:
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This looks like a great way to improve the current Primary bottleneck. Even if
the rebalancing isn't "smart" it would still distribute the load better than
currently.
Would load be redistributed after every change in node membership? That might
cause some load spikes if a cluster is started from zero, with all flows
starting on their backlogs while the nodes joining within seconds of eachother.
Maybe a rate limit to the rebalances should apply when adding nodes?
> "Single Node Only" Execution Node
> ---------------------------------
>
> Key: NIP-22
> URL: https://issues.apache.org/jira/browse/NIP-22
> Project: NiFi Improvement Proposal
> Issue Type: New Feature
> Reporter: Mark Payne
> Assignee: Mark Payne
> Priority: Major
>
> h3. Motivation
> NiFi supports running a Processor on "All Nodes" or "Primary Node Only." This
> works well when you have a few processors that don't require a large amount
> of overhead. However, some flows have many different processors that have to
> be run as Primary Node Only, and it can cause a single node to be heavily
> overloaded.
> There are times that we want to have a Primary Node because we want multiple
> flows running on the same node. But the vast majority of the time we simply
> care that the processor runs on 1 node only - but we don't care which node.
> To this end, we should introduce the ability to schedule a Processor to run
> on a "Single Node Only" but not care which node. If we have 100 Processors
> configured for Single Node Only, each node in the cluster should run some
> number of those Processors but not all. It is worth noting that we already
> have the necessary prerequisites in place for Leader Election, as we already
> use these for Primary Node and Cluster Coordinator - this simply allows for
> more leases to be used.
> h3. NiFi API Changes
> Introduce a new ExecutionNode value of `SINGLE_NODE_ONLY`.
> Deprecate the `@PrimaryNodeOnly` in favor of a new `@SingleNodeOnly`
> Introduce a new `@OnSingleNodeElectionChange` annotation that can be added to
> processors that is analogous to the @OnPrimaryNodeChange.
> h3. REST API Changes
> There should be no significant changes to the REST API, except to allow for
> the new Execution Node value.
> h3. UI Changes
> We will need a new icon similar to the 'P' badge that shows on Processors
> when the Processor is run on Primary Node Only. This also appears in the
> Summary table. We also need the ability to choose the new value for the
> "Execution Node".
> h3. Open Questions
> Do we truly have a need for Primary Node still? Or should this replace it
> entirely?
>
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