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// Copyright 2021 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//go:build go1.17
// +build go1.17
package internal
import (
"math"
"path"
"runtime/metrics"
"strings"
"github.com/prometheus/common/model"
)
// RuntimeMetricsToProm produces a Prometheus metric name from a runtime/metrics
// metric description and validates whether the metric is suitable for integration
// with Prometheus.
//
// Returns false if a name could not be produced, or if Prometheus does not understand
// the runtime/metrics Kind.
//
// Note that the main reason a name couldn't be produced is if the runtime/metrics
// package exports a name with characters outside the valid Prometheus metric name
// character set. This is theoretically possible, but should never happen in practice.
// Still, don't rely on it.
func RuntimeMetricsToProm(d *metrics.Description) (string, string, string, bool) {
namespace := "go"
comp := strings.SplitN(d.Name, ":", 2)
key := comp[0]
unit := comp[1]
// The last path element in the key is the name,
// the rest is the subsystem.
subsystem := path.Dir(key[1:] /* remove leading / */)
name := path.Base(key)
// subsystem is translated by replacing all / and - with _.
subsystem = strings.ReplaceAll(subsystem, "/", "_")
subsystem = strings.ReplaceAll(subsystem, "-", "_")
// unit is translated assuming that the unit contains no
// non-ASCII characters.
unit = strings.ReplaceAll(unit, "-", "_")
unit = strings.ReplaceAll(unit, "*", "_")
unit = strings.ReplaceAll(unit, "/", "_per_")
// name has - replaced with _ and is concatenated with the unit and
// other data.
name = strings.ReplaceAll(name, "-", "_")
name += "_" + unit
if d.Cumulative && d.Kind != metrics.KindFloat64Histogram {
name += "_total"
}
// Our current conversion moves to legacy naming, so use legacy validation.
valid := model.IsValidLegacyMetricName(namespace + "_" + subsystem + "_" + name)
switch d.Kind {
case metrics.KindUint64:
case metrics.KindFloat64:
case metrics.KindFloat64Histogram:
default:
valid = false
}
return namespace, subsystem, name, valid
}
// RuntimeMetricsBucketsForUnit takes a set of buckets obtained for a runtime/metrics histogram
// type (so, lower-bound inclusive) and a unit from a runtime/metrics name, and produces
// a reduced set of buckets. This function always removes any -Inf bucket as it's represented
// as the bottom-most upper-bound inclusive bucket in Prometheus.
func RuntimeMetricsBucketsForUnit(buckets []float64, unit string) []float64 {
switch unit {
case "bytes":
// Re-bucket as powers of 2.
return reBucketExp(buckets, 2)
case "seconds":
// Re-bucket as powers of 10 and then merge all buckets greater
// than 1 second into the +Inf bucket.
b := reBucketExp(buckets, 10)
for i := range b {
if b[i] <= 1 {
continue
}
b[i] = math.Inf(1)
b = b[:i+1]
break
}
return b
}
return buckets
}
// reBucketExp takes a list of bucket boundaries (lower bound inclusive) and
// downsamples the buckets to those a multiple of base apart. The end result
// is a roughly exponential (in many cases, perfectly exponential) bucketing
// scheme.
func reBucketExp(buckets []float64, base float64) []float64 {
bucket := buckets[0]
var newBuckets []float64
// We may see a -Inf here, in which case, add it and skip it
// since we risk producing NaNs otherwise.
//
// We need to preserve -Inf values to maintain runtime/metrics
// conventions. We'll strip it out later.
if bucket == math.Inf(-1) {
newBuckets = append(newBuckets, bucket)
buckets = buckets[1:]
bucket = buckets[0]
}
// From now on, bucket should always have a non-Inf value because
// Infs are only ever at the ends of the bucket lists, so
// arithmetic operations on it are non-NaN.
for i := 1; i < len(buckets); i++ {
if bucket >= 0 && buckets[i] < bucket*base {
// The next bucket we want to include is at least bucket*base.
continue
} else if bucket < 0 && buckets[i] < bucket/base {
// In this case the bucket we're targeting is negative, and since
// we're ascending through buckets here, we need to divide to get
// closer to zero exponentially.
continue
}
// The +Inf bucket will always be the last one, and we'll always
// end up including it here because bucket
newBuckets = append(newBuckets, bucket)
bucket = buckets[i]
}
return append(newBuckets, bucket)
}
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