[jira] [Created] (NIFI-8633) Content Repository can be improved to make fewer disks accesses on read

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

Mark Payne created NIFI-8633:
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             Summary: Content Repository can be improved to make fewer disks accesses on read
                 Key: NIFI-8633
                 URL: https://issues.apache.org/jira/browse/NIFI-8633
             Project: Apache NiFi
          Issue Type: Improvement
          Components: Core Framework
            Reporter: Mark Payne
            Assignee: Mark Payne


When {{FileSystemRepository.read(ContentClaim)}} or {{FileSystemRepository.read(ResourceClaim)}} is called, the repository determines the file path for the claim via {{getPath(claim, true);}} where the true indicates that we should verify that the file exists.

This is done so that if we were to pass in a ContentClaim that does not exist, we throw a more meaningful ContentNotFoundException instead of just letting a FileNotFoundException fly.

However, this call to {{Files.exists(Path)}} is fairly expensive, as it's a disk access. For a flow that uses a lot of smaller files, this can be extremely expensive.

We can improve this by removing the call to {{Files.exists}} all together. Instead, just blindly create the {{FileInputStream}} in a try/catch block and catch FileNotFoundException, and then wrap that in a {{ContentNotFoundException}}. This results in the same API and the same contracts as before but avoids the overhead of additional disk accesses/seeks.



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