[tor-bugs] #20405 [Metrics/metrics-lib]: create metrics-tools with all of the index.json processing code as first content

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#20405: create metrics-tools with all of the index.json processing code as first
content
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 Reporter:  iwakeh               |          Owner:  karsten
     Type:  enhancement          |         Status:  needs_information
 Priority:  Medium               |      Milestone:  metrics-lib 2.0.0
Component:  Metrics/metrics-lib  |        Version:
 Severity:  Normal               |     Resolution:
 Keywords:                       |  Actual Points:
Parent ID:                       |         Points:
 Reviewer:                       |        Sponsor:
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Changes (by karsten):

 * status:  new => needs_information


Comment:

 I gave this some more thoughts and am unconvinced that we need another
 library for index.json processing or similar code.

 Let's consider index.json processing here, because we already have that
 code.  The main purpose of extracting all code related to index.json
 production/consumption and putting it in a single place would be that we
 can change it in a single place quite easily.  And we can test it more
 easily.  Agreed, that would be useful.

 But let's take a closer look at how much overlap there's between the code
 in CollecTor and in metrics-lib:
  - CollecTor converts a directory tree to Java instances, serializes those
 to JSON, and writes the resulting index.json string to disk.
  - metrics-lib downloads the index.json file from a remote server,
 deserializes it to Java instances, and downloads contained files.

 The only code that could be shared here is the specification how Java
 instances are serialized to JSON and back.  That's not really much code,
 maybe a few dozen lines of code.  That's not nothing, but it's also hardly
 significant.

 But my main concern is that we'd create yet another library that makes it
 yet a bit harder for new contributors to see the big picture.  Maybe we'll
 need such a library in the future, but I don't see how we're there yet.

 Changing status to needs_information, in case I missed something important
 here.  But if not, I'd say let's close as wontfix.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20405#comment:4>
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