[tor-bugs] #20228 [Metrics/CollecTor]: Append all votes with same valid-after time to a single file in `recent/`

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#20228: Append all votes with same valid-after time to a single file in `recent/`
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 Reporter:  karsten            |          Owner:
     Type:  enhancement        |         Status:  needs_information
 Priority:  High               |      Milestone:
Component:  Metrics/CollecTor  |        Version:
 Severity:  Normal             |     Resolution:
 Keywords:                     |  Actual Points:
Parent ID:                     |         Points:
 Reviewer:                     |        Sponsor:
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Comment (by karsten):

 Okay, I see what you mean.  However, I'd rather want to advoid adding such
 a `@valid-after` tag, because it smells like making things more
 complicated than they should have to be.

 Here's what we could do.  We already have a list of missing
 microdescriptors in place for the downloader.  And we already parse
 incoming microdescriptor consensuses to learn about microdescriptors we'll
 want to fetch.  What we could do is: 1) always sync microdescriptor
 consensuses before microdescriptors, so that we learn about missing
 microdescriptors and their valid-after times; 2) look at the same map for
 sorting incoming microdescriptors into months; 3) discard microdescriptors
 we receive via sync that we're not missing.

 1) and 2) seem doable, but let's briefly think about the impact of 3)
 there.

 First, it seems rather unlikely that we'll run into that case very often,
 because we'd also sync microdescriptor consensuses from the other
 instance, so we should know all microdescriptors they know.

 Second, the value of microdescriptors is limited for most of our use
 cases, and the main reason for collecting them was to facilitate debugging
 Tor protocols but not to analyze the Tor network which is better done with
 consensuses and server descriptors.

 Third and last, let's keep in mind that we're improving descriptor
 completeness a lot with this sync approach, even if we might still be
 missing half a dozen microdescriptors per year.

 I'd say let's take the best-effort approach with microdescriptors and call
 it a day. :)

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/20228#comment:11>
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