[jira] [Created] (NIFI-11472) Make PutFTP processor more multithread friendly

["Daniel Salwerowicz (Jira)" <ji...@apache.org>]

Daniel Salwerowicz created NIFI-11472:
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             Summary: Make PutFTP processor more multithread friendly
                 Key: NIFI-11472
                 URL: https://issues.apache.org/jira/browse/NIFI-11472
             Project: Apache NiFi
          Issue Type: Bug
          Components: Core Framework
    Affects Versions: 1.21.0
         Environment: CentOS server, Java 11
            Reporter: Daniel Salwerowicz


Problem happens when a PutFTP is set to run several concurrent tasks and two (or more ) FlowFiles come in and both need to create the same directory. One of them will create directory and succeed immediately while the other will try to create directory, but fail since it already exist, throw an error, the FlowFile will then be penalized and on second run will succeed.

While it is not the biggest error, as files are getting transferred in the end, but the bulletins and errors are annoying, especially in production environment where you don't want to get unnecessary errors.

We found that the solution involves a simple change to the {{FTPTransfer.java}} class in:
{{nifi-nar-bundles/nifi-standard-bundle/nifi-standard-processors/src/main/java/org/apache/nifi/processors/standard/util/FTPTransfer.java}}
On line 398 and {{ensureDirectoryExists}} method you can simply add another if check which double checks that the directory exists when it fails to create one.
{code:java}
final boolean cdSuccessful = setWorkingDirectory(remoteDirectory);

if (!cdSuccessful) {    
  if (client.makeDirectory(remoteDirectory)) {        
    logger.debug("Remote Directory not found: created directory [{}]", remoteDirectory);    
  } else if (setWorkingDirectory(remoteDirectory)) { 
         // Double check that the dir exists as it might have been created in another thread        
    throw new IOException("Failed to create remote directory " + remoteDirectory);    
  }
}{code}
We have created a fix and will submit it as a Pull Request on GitHub



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