[tor-bugs] #20039 [Metrics/metrics-lib]: integrate `DescriptorIndexCollector` in a fully backward-compatible way

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#20039: integrate `DescriptorIndexCollector` in a fully backward-compatible way
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 Reporter:  iwakeh               |          Owner:  iwakeh
     Type:  enhancement          |         Status:  assigned
 Priority:  Medium               |      Milestone:  metrics-lib 1.5.0
Component:  Metrics/metrics-lib  |        Version:
 Severity:  Normal               |     Resolution:
 Keywords:                       |  Actual Points:
Parent ID:                       |         Points:
 Reviewer:                       |        Sponsor:
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Comment (by iwakeh):

 Please review [https://gitweb.torproject.org/user/iwakeh/metrics-
 lib.git/commit/?h=task-20039-index&id=2ba737c518547ce003be3e207b105030aa88eb43
 this branch] containing the changes discussed in Berlin (comment:1 and
 comment:2).

 The changes here and in #19934 made the *Node classes even smaller by
 transferring code to either DescriptorIndexDownloader here in metrics-lib
 or to CreateIndexJson in CollecTor.

 === This solution is not ideal
 The four classes FileType, FileNode, DirectoryNode, and IndexNode are
 currently maintained in both collector and metrics-lib.  Eventually, there
 should be only one place for them. It seems that the duplicate maintenance
 effort will most likely cause more work in the long run than extending
 metrics-lib's api by these four files.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20039#comment:3>
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