[tor-bugs] #12656 [Onionoo]: Calculating path selection probabilities shouldn't depend on parsing a new consensus

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#12656: Calculating path selection probabilities shouldn't depend on parsing a new
consensus
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 Reporter:  karsten  |          Owner:  karsten
     Type:  defect   |         Status:  new
 Priority:  normal   |      Milestone:
Component:  Onionoo  |        Version:
 Keywords:           |  Actual Points:
Parent ID:           |         Points:
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 The current implementation in NodeDetailsStatusUpdater calculates guard,
 middle, and exit probability using bandwidth weights (Wgg, Wgd, etc.) from
 the most recent of all parsed consensuses.  This approach breaks if no
 consensus was parsed, and as a result, all relays' guard/middle/exit
 probabilities are set to 0.0.  This happend a few days ago, because it
 took CollecTor more than 10 minutes to fetch and provide a current
 consensus from the directory authorities, which was too late for the
 hourly Onionoo run.

 This is also bad design, because right now, JSON documents depend on more
 than what's contained in internal status files.  We may want to add a mode
 of operation that rewrites all JSON documents.  That is currently not
 possible.

 A possible fix would be to make all attributes of NodeStatus persistent.
 The downside is that we may not need those contents in the servlet, so
 this change would needlessly slow down populating the servlet's search
 index.

 Another fix would be to move ''all'' non-persistent attributes from
 NodeStatus to DetailsStatus.  That includes guard/middle/exit
 probabilities, but maybe also other fields.  Not sure about downsides yet.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/12656>
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