[tor-bugs] #31493 [Circumvention/Snowflake]: Add a version to the metrics output

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#31493: Add a version to the metrics output
-------------------------------------+------------------------------
 Reporter:  cohosh                   |          Owner:  cohosh
     Type:  defect                   |         Status:  needs_review
 Priority:  Medium                   |      Milestone:
Component:  Circumvention/Snowflake  |        Version:
 Severity:  Normal                   |     Resolution:
 Keywords:                           |  Actual Points:
Parent ID:                           |         Points:
 Reviewer:                           |        Sponsor:  Sponsor28
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Comment (by cohosh):

 I updated https://github.com/cohosh/snowflake/compare/bug31493 to use the
 following spec:

 {{{
 We export metrics in the following (version 1.0) format:

     "snowflake-stats-end" YYYY-MM-DD HH:MM:SS (NSEC s) NL
         [At start, exactly once.]

         YYYY-MM-DD HH:MM:SS defines the end of the included measurement
         interval of length NSEC seconds (86400 seconds by default).

     "@type snowflake-stats 1.0"
         [Exactly once.]

         Defines the version of snowflake stats output being used
         (currently 1.0)

     "snowflake-ips" CC=NUM,CC=NUM,... NL
         [At most once.]

         List of mappings from two-letter country codes to the number of
         unique IP addresses of snowflake proxies that have polled.

     "snowflake-ips-total" NUM NL
         [At most once.]

         A count of the total number of unique IP addresses of snowflake
         proxies that have polled.

     "snowflake-idle-count" NUM NL
         [At most once.]

         A count of the number of times a proxy has polled but received
         no client offer, rounded up to the nearest multiple of 8.

     "client-denied-count" NUM NL
         [At most once.]

         A count of the number of times a client has requested a proxy
         from the broker but no proxies were available, rounded up to
         the nearest multiple of 8.

     "client-snowflake-match-count" NUM NL
         [At most once.]

         A count of the number of times a client successfully received a
         proxy from the broker, rounded up to the nearest multiple of 8.
 }}}

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/31493#comment:4>
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