[jira] [Commented] (NIP-22) "Single Node Only" Execution Node

["Florian Beck (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/NIP-22?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18084224#comment-18084224 ] 

Florian Beck commented on NIP-22:
---------------------------------

This sounds great, but i also ran often in scenarios when i want to use only a fixed node to be sure i have 100% the correct ordering. After a unscheduled downtime of a primary node, the jobs are handled by the new primary. Its just a mess, when the old primary comes up with non empty queues.  

> "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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