[tahoe-lafs-trac-stream] [Tahoe-LAFS] #2788: add connection-policy configuration

[Tahoe-LAFS]

#2788: add connection-policy configuration
------------------------------+-----------------------
     Reporter:  warner        |      Owner:  warner
         Type:  enhancement   |     Status:  new
     Priority:  normal        |  Milestone:  undecided
    Component:  code-network  |    Version:  1.11.0
   Resolution:                |   Keywords:
Launchpad Bug:                |
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Comment (by warner):

 dawuud reminded me that connections.yaml was also supposed to hold the
 multiple-introducer config. The proposed section was called `introducers`
 and contained a dictionary mapping introducer-petname to a dictionary with
 one defined key named `furl`:

 {{{
 introducers:
   intro-name-1:
     furl: pb://tubid@hints/swissnum
   intro-name-2:
     furl: pb://tubid@hints/swissnum
 }}}

 (note that the original patch used "nickname" instead of "petname", which
 I think is inconsistent because this name is being chosen by the local
 client, whereas a "nickname", in our usage, is chosen by the object being
 named)

 Since this is basically just a list of (petname, furl) tuples, I don't
 think we need the full power of YAML to represent it. So I'm thinking it
 can go into `tahoe.cfg`, right next to the old `introducer.furl=` key. We
 just declare that every key which matches `introducer-.*\.furl` is adding
 an introducer, and the part after the dash is the petname. This limits the
 petnames somewhat (no spaces, no dots, no punctuation), but I don't think
 that's a big deal.

 We can still use the petnames to build filenames for the local cache. The
 normal introducer has a petname of "" and uses
 `private/introducer_cache.yaml`. A `tahoe.cfg` key of `introducer-
 local.furl = pb://etc` would have a petname of `local` and would use
 `private/introducer_cache_local.yaml`.

--
Ticket URL: <https://tahoe-lafs.org/trac/tahoe-lafs/ticket/2788#comment:24>
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