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### Describe Your Changes
In most cases histograms are exposed in sorted manner with lower buckets
being first. This means that during scraping buckets with lower bounds
have higher chance of being updated earlier than upper ones.
Previously, values were propagated from upper to lower bounds, which
means that in most cases that would produce results higher than expected
once all buckets will become updated.
Propagating from upper bound effectively limits highest value of
histogram to the value of previous scrape. Once the data will become
consistent in the subsequent evaluation this causes spikes in the
result.
Changing propagation to be from lower to higher buckets reduces value
spikes in most cases due to nature of the original inconsistency.
See: https://github.com/VictoriaMetrics/VictoriaMetrics/issues/4580
An example histogram with previous(red) and updated(blue) versions:
This also makes logic of filling nan values with lower buckets values: [1 2 3 nan nan nan] => [1 2 3 3 3 3] obsolete.
Since buckets are now fixed from lower ones to upper this happens in the main loop, so there is no need in a second one.
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Signed-off-by: Zakhar Bessarab <z.bessarab@victoriametrics.com>
Signed-off-by: hagen1778 <roman@victoriametrics.com>
Co-authored-by: Andrii Chubatiuk <andrew.chubatiuk@gmail.com>
Co-authored-by: hagen1778 <roman@victoriametrics.com>
(cherry picked from commit
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| .. | ||
| active_queries.go | ||
| aggr_incremental_test.go | ||
| aggr_incremental.go | ||
| aggr_test.go | ||
| aggr.go | ||
| binary_op.go | ||
| eval_test.go | ||
| eval.go | ||
| exec_test.go | ||
| exec.go | ||
| memory_limiter_test.go | ||
| memory_limiter.go | ||
| parser.go | ||
| rollup_result_cache_test.go | ||
| rollup_result_cache.go | ||
| rollup_test.go | ||
| rollup_timing_test.go | ||
| rollup.go | ||
| timeseries_test.go | ||
| timeseries.go | ||
| transform_test.go | ||
| transform.go | ||
| tzdata.go | ||