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Re: [tor-bugs] #26022 [Metrics/Statistics]: Fix a flaw in the noise-removing code in our onion service statistics
#26022: Fix a flaw in the noise-removing code in our onion service statistics
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Reporter: karsten | Owner: metrics-team
Type: defect | Status: needs_review
Priority: Medium | Milestone:
Component: Metrics/Statistics | Version:
Severity: Normal | Resolution:
Keywords: | Actual Points:
Parent ID: | Points:
Reviewer: | Sponsor:
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Comment (by karsten):
Here's an updated version of the graph from comment 5 that also goes back
to late 2014 when we started gathering onion service statistics:
[[Image(hidserv-change-full-task-26022.png, 700px)]]
Some thoughts:
- Some of the numbers for 2015 produced by the fixed `removeNoise()`
method are up to 15% smaller than those from the flawed method. During
2015, very few relays were reporting onion service statistics, with the
[https://metrics.torproject.org/hidserv-frac-
reporting.html?start=2014-10-01&end=2018-05-17 fraction not going up
before late 2015]. The reason for new values being smaller than old values
is that we're not erroneously adding `bin_size` to negative reported
statistics anymore.
- There are very few cases in the first half of 2015 where new values are
much larger than old values. I believe this is related to another bug in
our code that made us terminate the module immediately if a consensus did
not contain a `bandwidth-weights` line. I'm going to fix that, too, but
it's unrelated to the flawed `removeNoise()` method.
- The numbers starting in 2016 are almost the same in the new and old
approach. That's what the previous graph in comment 5 showed, too.
All in all, I'd say the fixed `removeNoise()` method works just fine.
I'm starting another run now that uses the simplified `removeNoise()`
method that only subtracts `bin_size` and does no
rounding/truncating/flooring at all (as suggested earlier). That will take
12+ hours.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26022#comment:14>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
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