[jira] [Created] (NIFI-8340) If content repository is filling up, create bulletin when exerting backpressure

["Mark Payne (Jira)" <ji...@apache.org>]

Mark Payne created NIFI-8340:
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             Summary: If content repository is filling up, create bulletin when exerting backpressure
                 Key: NIFI-8340
                 URL: https://issues.apache.org/jira/browse/NIFI-8340
             Project: Apache NiFi
          Issue Type: Improvement
          Components: Core Framework
            Reporter: Mark Payne


When the content repository reaches its configured threshold (by default, 50%), it will exert backpressure that prevents any component from writing to it until archive has occurred. This is designed to prevent a case where the content repository is written to so fast that cleanup is unable to keep up. This can be important for use cases where there is extremely high throughput and the nodes are pretty well tapped out resource-wise.

However, when this happens, it's not at all obvious to the user, as it only shows an INFO level message in the logs. As a result, users who encounter this typically think NiFi just suddenly "froze."

To improve the experience here, we should do the following:
 * Change default to something less restrictive, such as 75 or 80%. For dev environments, especially, the content repository is not by itself and it's common for the drive to be more than 50% full before NiFi is even installed.
 * Change the log message from INFO to WARN
 * Create a Bulletin at the Controller Level that warns that backpressure is being applied. Ideally, this could even be created at the component level, but it's not clear that this is possible without significant refactoring, as the Content Repository does not know which component is trying to write to it.



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