Last Comment Bug 764585 - make it even harder to get enumerated histograms wrong
: make it even harder to get enumerated histograms wrong
Product: Toolkit
Classification: Components
Component: Telemetry (show other bugs)
: unspecified
: All All
-- normal (vote)
: mozilla18
Assigned To: Nathan Froyd [:froydnj]
: Georg Fritzsche [:gfritzsche]
Depends on: 781200 785959
Blocks: 763359
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Reported: 2012-06-13 14:23 PDT by Nathan Froyd [:froydnj]
Modified: 2012-08-29 06:40 PDT (History)
3 users (show)
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patch (1.25 KB, patch)
2012-08-28 10:46 PDT, Nathan Froyd [:froydnj]
taras.mozilla: review+
Details | Diff | Splinter Review

Description User image Nathan Froyd [:froydnj] 2012-06-13 14:23:28 PDT
Bug 763359, comment 3:

Because multiple teams got tripped up by this, I highly recommend that we change the API so that one **cannot** create a linear histogram from (1-n) with n buckets, by adding a MOZ_STATIC_ASSERT for that condition. For the case where this is a false positive, the person who defines the telemetry can just change the bucket count to (n+1). For the case where this check would prevent a problem, it will avoid collecting bad data.
Comment 1 User image (dormant account) 2012-06-13 15:45:08 PDT
Comment 2 User image :Ehsan Akhgari 2012-06-14 14:22:08 PDT
there's at least one sample of this for the macros.
Comment 3 User image :Ehsan Akhgari 2012-06-14 14:44:42 PDT
(In reply to Ehsan Akhgari [:ehsan] from comment #2)
> there's at least one sample of this for the macros.

That is,

Turns out that bugzilla comments typed in on a phone aren't that useful!
Comment 4 User image David Bolter [:davidb] 2012-06-19 10:55:23 PDT
This blocks a FF 14 tracked bug.
Comment 5 User image Nathan Froyd [:froydnj] 2012-08-28 10:46:45 PDT
Created attachment 656089 [details] [diff] [review]

This patch adds a check for high > n_buckets for both linear and exponential histograms, in an attempt to eliminate the common mistake of using a linear histogram with high == n_buckets == N to record values from 1 to N.  It's still possible to make errors, of course, but I think this is the best we can do short of rewriting how the histogram code at its core works.  WDYT?
Comment 6 User image (dormant account) 2012-08-28 10:55:23 PDT
Comment on attachment 656089 [details] [diff] [review]

Comment 8 User image Ed Morley [:emorley] 2012-08-29 06:40:40 PDT

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