[jira] [Created] (NIFI-6462) ListHDFS should be triggerable

["Alessandro D'Armiento (JIRA)" <ji...@apache.org>]

Alessandro D'Armiento created NIFI-6462:
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             Summary: ListHDFS should be triggerable
                 Key: NIFI-6462
                 URL: https://issues.apache.org/jira/browse/NIFI-6462
             Project: Apache NiFi
          Issue Type: Improvement
          Components: Core Framework
    Affects Versions: 1.9.2
            Reporter: Alessandro D'Armiento


h2. Current Situation

ListHDFS is designed to be (only) the entry point of a data integration pipeline, and therefore can only be triggered on a cron or time base. 

h2. Improvement Proposal

ListHDFS should be able to be used as part of your pipeline even if you do not expect to have it as the entry point. To obtain it: 
* It has to be triggerable
* Trigger flowfile should be able to bring the listing directory as an attribute
* Some logic, such as the "skip the last file in the listing directory" should be made optional
* Since the processor will work on a 1:N semantic (1 input trigger flowfile, N output flowfiles) it would be nice to support fragmentation attributes (for example for subsequent merge operations)
  * It would be also useful to support different fragmentation strategies, in order to support multiple user cases. For example, it should be possible to select:
    *  A "one for all" fragmentation strategy which will create a single fragmentation group. Therefore, all files will have the same fragment.identifier, the same fragment.count, equal to the total number N of listed files, and fragment.index ∈ [0, N).
    *  A "per subdir" fragmentation strategy which will create different fragmentation groups, one for each scanned subdirectory of the given path. Therefore, for each subfolder, flowfiles will have a specific fragment.identifier, fragment.count will be, for each flowfile, equal to the number Ni of files in the i-th directory, and fragment.index ∈ [0, Ni).




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