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ccfe14d7e7
promql: Improve histogram_quantile calculation for classic buckets Tiny differences between classic buckets are most likely caused by floating point precision issues. With this commit, relative changes below a certain threshold are ignored. This makes the result of histogram_quantile more meaningful, and also avoids triggering the _input to histogram_quantile needed to be fixed for monotonicity_ annotations in unactionable cases. This commit also adds explanation of the new adjustment and of the monotonicity annotation to the documentation of `histogram_quantile`. --------- Signed-off-by: Jeanette Tan <jeanette.tan@grafana.com>
319 lines
7.1 KiB
Go
319 lines
7.1 KiB
Go
// Copyright 2023 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package promql
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import (
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"math"
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"testing"
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"github.com/stretchr/testify/require"
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)
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func TestBucketQuantile_ForcedMonotonicity(t *testing.T) {
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eps := 1e-12
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for name, tc := range map[string]struct {
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getInput func() buckets // The buckets can be modified in-place so return a new one each time.
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expectedForced bool
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expectedFixed bool
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expectedValues map[float64]float64
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}{
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"simple - monotonic": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 10,
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count: 10,
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}, {
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upperBound: 15,
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count: 15,
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}, {
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upperBound: 20,
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count: 15,
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}, {
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upperBound: 30,
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count: 15,
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}, {
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upperBound: math.Inf(1),
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count: 15,
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},
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}
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},
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expectedForced: false,
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expectedFixed: false,
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expectedValues: map[float64]float64{
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1: 15.,
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0.99: 14.85,
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0.9: 13.5,
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0.5: 7.5,
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},
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},
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"simple - non-monotonic middle": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 10,
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count: 10,
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}, {
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upperBound: 15,
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count: 15,
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}, {
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upperBound: 20,
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count: 15.00000000001, // Simulate the case there's a small imprecision in float64.
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}, {
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upperBound: 30,
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count: 15,
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}, {
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upperBound: math.Inf(1),
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count: 15,
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},
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}
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},
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expectedForced: false,
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expectedFixed: true,
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expectedValues: map[float64]float64{
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1: 15.,
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0.99: 14.85,
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0.9: 13.5,
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0.5: 7.5,
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},
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},
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"real example - monotonic": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 1,
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count: 6454661.3014166197,
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}, {
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upperBound: 5,
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count: 8339611.2001912938,
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}, {
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upperBound: 10,
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count: 14118319.2444762159,
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}, {
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upperBound: 25,
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count: 14130031.5272856522,
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}, {
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upperBound: 50,
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count: 46001270.3030008152,
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}, {
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upperBound: 64,
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count: 46008473.8585563600,
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}, {
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upperBound: 80,
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count: 46008473.8585563600,
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}, {
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upperBound: 100,
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count: 46008473.8585563600,
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}, {
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upperBound: 250,
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count: 46008473.8585563600,
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}, {
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upperBound: 1000,
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count: 46008473.8585563600,
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}, {
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upperBound: math.Inf(1),
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count: 46008473.8585563600,
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},
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}
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},
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expectedForced: false,
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expectedFixed: false,
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expectedValues: map[float64]float64{
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1: 64.,
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0.99: 49.64475715376406,
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0.9: 46.39671690938454,
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0.5: 31.96098248992002,
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},
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},
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"real example - non-monotonic": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 1,
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count: 6454661.3014166225,
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}, {
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upperBound: 5,
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count: 8339611.2001912957,
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}, {
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upperBound: 10,
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count: 14118319.2444762159,
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}, {
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upperBound: 25,
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count: 14130031.5272856504,
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}, {
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upperBound: 50,
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count: 46001270.3030008227,
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}, {
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upperBound: 64,
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count: 46008473.8585563824,
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}, {
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upperBound: 80,
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count: 46008473.8585563898,
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}, {
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upperBound: 100,
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count: 46008473.8585563824,
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}, {
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upperBound: 250,
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count: 46008473.8585563824,
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}, {
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upperBound: 1000,
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count: 46008473.8585563898,
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}, {
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upperBound: math.Inf(1),
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count: 46008473.8585563824,
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},
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}
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},
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expectedForced: false,
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expectedFixed: true,
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expectedValues: map[float64]float64{
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1: 64.,
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0.99: 49.64475715376406,
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0.9: 46.39671690938454,
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0.5: 31.96098248992002,
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},
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},
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"real example 2 - monotonic": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 0.005,
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count: 9.6,
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}, {
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upperBound: 0.01,
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count: 9.688888889,
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}, {
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upperBound: 0.025,
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count: 9.755555556,
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}, {
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upperBound: 0.05,
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count: 9.844444444,
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}, {
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upperBound: 0.1,
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count: 9.888888889,
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}, {
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upperBound: 0.25,
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count: 9.888888889,
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}, {
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upperBound: 0.5,
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count: 9.888888889,
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}, {
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upperBound: 1,
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count: 9.888888889,
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}, {
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upperBound: 2.5,
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count: 9.888888889,
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}, {
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upperBound: 5,
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count: 9.888888889,
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}, {
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upperBound: 10,
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count: 9.888888889,
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}, {
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upperBound: 25,
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count: 9.888888889,
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}, {
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upperBound: 50,
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count: 9.888888889,
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}, {
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upperBound: 100,
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count: 9.888888889,
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}, {
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upperBound: math.Inf(1),
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count: 9.888888889,
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},
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}
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},
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expectedForced: false,
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expectedFixed: false,
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expectedValues: map[float64]float64{
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1: 0.1,
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0.99: 0.03468750000281261,
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0.9: 0.00463541666671875,
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0.5: 0.0025752314815104174,
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},
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},
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"real example 2 - non-monotonic": {
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getInput: func() buckets {
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return buckets{
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{
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upperBound: 0.005,
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count: 9.6,
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}, {
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upperBound: 0.01,
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count: 9.688888889,
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}, {
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upperBound: 0.025,
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count: 9.755555556,
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}, {
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upperBound: 0.05,
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count: 9.844444444,
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}, {
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upperBound: 0.1,
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count: 9.888888889,
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}, {
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upperBound: 0.25,
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count: 9.888888889,
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}, {
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upperBound: 0.5,
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count: 9.888888889,
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}, {
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upperBound: 1,
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count: 9.888888889,
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}, {
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upperBound: 2.5,
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count: 9.888888889,
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}, {
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upperBound: 5,
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count: 9.888888889,
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}, {
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upperBound: 10,
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count: 9.888888889001, // Simulate the case there's a small imprecision in float64.
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}, {
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upperBound: 25,
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count: 9.888888889,
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}, {
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upperBound: 50,
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count: 9.888888888999, // Simulate the case there's a small imprecision in float64.
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}, {
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upperBound: 100,
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count: 9.888888889,
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}, {
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upperBound: math.Inf(1),
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count: 9.888888889,
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},
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}
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},
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expectedForced: false,
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expectedFixed: true,
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expectedValues: map[float64]float64{
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1: 0.1,
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0.99: 0.03468750000281261,
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0.9: 0.00463541666671875,
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0.5: 0.0025752314815104174,
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},
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},
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} {
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t.Run(name, func(t *testing.T) {
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for q, v := range tc.expectedValues {
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res, forced, fixed := bucketQuantile(q, tc.getInput())
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require.Equal(t, tc.expectedForced, forced)
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require.Equal(t, tc.expectedFixed, fixed)
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require.InEpsilon(t, v, res, eps)
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}
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})
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}
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}
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