[tor-bugs] #11683 [Tor]: Stop caching extra-info documents on directory mirrors

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#11683: Stop caching extra-info documents on directory mirrors
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 Reporter:  karsten      |          Owner:
     Type:  enhancement  |         Status:  new
 Priority:  normal       |      Milestone:  Tor: 0.2.???
Component:  Tor          |        Version:
 Keywords:  tor-relay    |  Actual Points:
Parent ID:               |         Points:
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 I suggest stopping to cache extra-info documents on directory mirrors.

 Most clients don't need extra-info documents for their normal operation.
 The only use case that comes to mind is external tools configuring a local
 tor client to provide them with extra-info documents.  Note that we
 wouldn't break these tools, because they could still fetch from the
 directory authorities.  Though I assume there are very few requests for
 extra-info documents in the network.

 There are also not many directory mirrors in the network that serve extra-
 info documents: in the first weeks of April 2014, only 0.46% of server
 descriptors contained the `"caches-extra-info"` line, so 0.46% * 5,000 =
 23 relays.  Note that 9 of these are directory authorities and only 14 are
 directory mirrors.

 But still, these 14 directory mirrors need to keep their cache up-to-date
 by fetching extra-info documents from the directory authorities.  If there
 are fewer than 14 clients downloading extra-info documents from the
 caches, the caches put even more load on directory authorities just to
 keep their caches recent.

 All in all, I'd say let's get rid of extra-info documents on directory
 mirrors.  I can write a patch, unless somebody else enjoys removing
 (mostly) unused code as much as I do.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/11683>
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