[tor-bugs] #5651 [Metrics Utilities]: Annotation header with descriptor types

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#5651: Annotation header with descriptor types
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 Reporter:  atagar             |          Owner:     
     Type:  enhancement        |         Status:  new
 Priority:  normal             |      Milestone:     
Component:  Metrics Utilities  |        Version:     
 Keywords:                     |         Parent:     
   Points:                     |   Actualpoints:     
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Comment(by atagar):

 > How about we add an annotation line @type descriptor-type major.minor as
 the new first line of a descriptor?

 Sounds great! In an ideal world the header would answer three questions...
 - what type of descriptor am I trying to parse?
 - among my parsing methods, which should I use?
 - if this isn't a recognized version then should I still parse it, or does
 the change break backward compatibility?

 I'm not sure if the third is something that we want to answer via the
 header or not. Usually that's distinguished via major versions and minor
 versions, but here it's a tor version and metrics version instead.

 How would you like our libraries to handle unrecognized versions? Abort?
 Attempt to parse anyway? Somehow decide based on the version?

 > We might want to reserve @type in dir-spec.txt, or we may run into
 trouble once Tor writes such an annotation itself.

 Probably not needed. Annotations aren't part of the dir-spec since they
 reside outside of the descriptor itself. When I asked about them I was
 told that they're a tor implementation detail and hence something liable
 to change at any time.

 That said, this might be an exception since it's used outside of tor
 itself. Regardless, it would be nice if we added the @type annotation to
 tor's cached descriptors too...

 Cheers! -Damian

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5651#comment:2>
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