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Navigate to the running Flow Execution and click the 'Kill' button to stop the current execution and synchronize synchronize the job aborted status in to RED.
Cleaning up after killing jobs in Azkaban
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Aborting a job from the RED UI is possible from RED 10.5+ but this action does not synchronize the related Azkaban execution so should really only be used when your Azkaban execution has finished but RED UI is showing it as still running. . An alternative approach is to use the restart failed execution method from Azkaban Dashboard which which is detailed here.
A job can be aborted by right-clicking the job in the RED Scheduler window and choosing Abort Job from the context menu.
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