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Do not count the +Inf bucket for bucket creation. 

Add explanation for DefBuckets.
This commit is contained in:
beorn7 2015-02-19 12:40:29 +01:00
parent 4c4f51d546
commit 3e50eddd64
3 changed files with 21 additions and 19 deletions
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2
prometheus/examples_test.go
View File

@ -457,7 +457,7 @@ func ExampleHistogram() {
temps := prometheus.NewHistogram(prometheus.HistogramOpts{
Name: "pond_temperature_celsius",
Help: "The temperature of the frog pond.", // Sorry, we can't measure how badly it smells.
Buckets: prometheus.LinearBuckets(20, 5, 6), // 6 buckets, each 5 centigrade wide.
Buckets: prometheus.LinearBuckets(20, 5, 5), // 5 buckets, each 5 centigrade wide.
})
// Simulate some observations.

34
prometheus/histogram.go
View File

@ -47,23 +47,25 @@ type Histogram interface {
Observe(float64)
}
// DefBuckets are the default Histogram buckets. Most likely, you want to define
// buckets customized to your use case.
// DefBuckets are the default Histogram buckets. The default buckets are
// tailored to broadly measure response time in seconds for a typical online
// serving system. Most likely, however, you will be required to define buckets
// customized to your use case.
var (
DefBuckets = []float64{.005, .01, .025, .05, .1, .25, .5, 1, 2.5, 5, 10}
)
// LinearBuckets creates 'count' buckets, each 'width' wide, where the lowest
// bucket has an upper bound of 'start'. The final +Inf bucket is counted
// towards the total 'count', but not included in the returned slice. The
// returned slice is meant to be used for the Buckets field of HistogramOpts.
// bucket has an upper bound of 'start'. The final +Inf bucket is not counted
// and not included in the returned slice. The returned slice is meant to be
// used for the Buckets field of HistogramOpts.
//
// The function panics if 'count' is less than 2.
// The function panics if 'count' is zero or negative.
func LinearBuckets(start, width float64, count int) []float64 {
if count < 2 {
panic("LinearBuckets needs a count > 1")
if count < 1 {
panic("LinearBuckets needs a positive count")
}
buckets := make([]float64, count-1)
buckets := make([]float64, count)
for i := range buckets {
buckets[i] = start
start += width
@ -73,15 +75,15 @@ func LinearBuckets(start, width float64, count int) []float64 {
// ExponentialBuckets creates 'count' buckets, where the lowest bucket has an
// upper bound of 'start' and each following bucket's upper bound is 'factor'
// times the previous bucket's upper bound. The final +Inf bucket is counted
// towards the total 'count', but not included in the returned slice. The
// returned slice is meant to be used for the Buckets field of HistogramOpts.
// times the previous bucket's upper bound. The final +Inf bucket is not counted
// and not included in the returned slice. The returned slice is meant to be
// used for the Buckets field of HistogramOpts.
//
// The function panics if 'count' is less than 2, if 'start' is 0 or negative,
// The function panics if 'count' is 0 or negative, if 'start' is 0 or negative,
// or if 'factor' is less than or equal 1.
func ExponentialBuckets(start, factor float64, count int) []float64 {
if count < 2 {
panic("ExponentialBuckets needs a count > 1")
if count < 1 {
panic("ExponentialBuckets needs a positive count")
}
if start <= 0 {
panic("ExponentialBuckets needs a positive start value")
@ -89,7 +91,7 @@ func ExponentialBuckets(start, factor float64, count int) []float64 {
if factor <= 1 {
panic("ExponentialBuckets needs a factor greater than 1")
}
buckets := make([]float64, count-1)
buckets := make([]float64, count)
for i := range buckets {
buckets[i] = start
start *= factor

4
prometheus/histogram_test.go
View File

@ -304,13 +304,13 @@ func getCumulativeCounts(vars []float64) []uint64 {
}
func TestBuckets(t *testing.T) {
got := LinearBuckets(-15, 5, 7)
got := LinearBuckets(-15, 5, 6)
want := []float64{-15, -10, -5, 0, 5, 10}
if !reflect.DeepEqual(got, want) {
t.Errorf("linear buckets: got %v, want %v", got, want)
}
got = ExponentialBuckets(100, 1.2, 4)
got = ExponentialBuckets(100, 1.2, 3)
want = []float64{100, 120, 144}
if !reflect.DeepEqual(got, want) {
t.Errorf("linear buckets: got %v, want %v", got, want)