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https://issues.apache.org/jira/browse/NIFI-6900?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Mark Payne resolved NIFI-6900.
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Fix Version/s: 1.15.0
Resolution: Fixed
> Request to retrieve flow in clustered environment should be much less
> expensive
> -------------------------------------------------------------------------------
>
> Key: NIFI-6900
> URL: https://issues.apache.org/jira/browse/NIFI-6900
> Project: Apache NiFi
> Issue Type: Improvement
> Components: Core Framework
> Reporter: Mark Payne
> Priority: Major
> Labels: cluster, dto, performance, ui
> Fix For: 1.15.0
>
>
> When a request is made to the `/nifi-api/flow/process-groups/\{pgId}`
> endpoint, the request must be replicated and the responses merged. The things
> that need to be merged include bulletins, component permissions, statuses,
> load balance indicators, validation errors, and perhaps a few others.
> However, each node currently responds with a fully populated
> `ProcessGroupFlowEntity`. This entity contains all information that is needed
> to display the current Process Group in the UI, as well as a lot of other
> details. For example, it contains the Property Descriptors for every
> component, including the property description, default value, etc. These
> should only be needed when configuring a component, not to display the canvas.
> This request can take a while when the flow is large or when the cluster is
> large, because the JSON must be parsed from every node in the cluster in
> order to merge the responses. Profiling shows that the expense can be broken
> down into two functions: parsing the nodes' responses into DTO objects and
> merging the responses, with parsing being the dominant function in terms of
> cost (over 80%).
> There are two big improvements that I think can be made:
> * Null out some things from the DTO before returning the response. Things
> like Property Descriptors, Property Values, and most all component
> configuration. These should be fetched when the component is configured.
> However, this change may require significant changes to the UI, as well.
> * Add a query parameter to the endpoint such as `minimal=true`. This query
> parameter would default to `false` in order to maintain backward
> compatibility but if set to `true`, the response would contain only the
> information needed in order to assemble a fully response to the client. To
> accomplish this, one response would need to be fully populated (likely, this
> would be whichever node is the Cluster Coordinator) and that response would
> include a 'fullyPopulated' flag. This would be the 'clientResponse' that is
> used when merging the node responses. All other nodes would first null out
> the elements that are not required for merging. So it would include things
> like the bulletins, validation errors, status, etc. Even the status could be
> further reduced by not including the "human readable" values but only the raw
> numeric values, since the human readable values are ignored when merging
> anyway.
> This would significantly reduce the amount of time taken to replicate this
> request, which would provide the user with a far better experience due to the
> significantly shorter response times.
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