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measure.go
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measure.go
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package stats
import (
"reflect"
"sort"
"strings"
"sync"
"sync/atomic"
"unsafe"
)
// Measure is a type that represents a single measure made by the application.
// Measures are identified by a name, a set of fields that define what has been
// instrumented, and a set of tags representing different dimensions of the
// measure.
//
// Implementations of the Handler interface receive lists of measures produced
// by the application, and assume the tags will be sorted.
type Measure struct {
Name string
Fields []Field
Tags []Tag
}
// Clone creates and returns a deep copy of m. The original and returned values
// and do not share any pointers to mutable types (but may share string values
// for example).
func (m Measure) Clone() Measure {
return Measure{
Name: m.Name,
Fields: copyFields(m.Fields),
Tags: copyTags(m.Tags),
}
}
func (m Measure) String() string {
return "{ " + m.Name + "(" + strings.Join(stringFields(m.Fields), ", ") + ") [" + strings.Join(stringTags(m.Tags), ", ") + "] }"
}
func stringFields(fields []Field) []string {
s := make([]string, len(fields))
for i, f := range fields {
s[i] = f.String()
}
return s
}
func stringTags(tags []Tag) []string {
s := make([]string, len(tags))
for i, t := range tags {
s[i] = t.String()
}
return s
}
// MakeMeasures takes a struct value or a pointer to a struct value as argument
// and extracts and returns the list of measures that it represented.
//
// The rules for converting values to measure are:
//
// 1. All fields exposing a 'metric' tag are expected to be of type bool, int,
// int8, int16, int32, int64, uint, uint8, uint16, uint32, uint64, uintptr,
// float32, float64, or time.Duration, and represent fields of the measures.
// The struct fields may also define a 'type' tag with a value of "counter",
// "gauge" or "histogram" to tune the behavior of the measure handlers.
//
// 2. All fields exposing a 'tag' tag are expected to be of type string and
// represent tags of the measures.
//
// 3. All struct fields are searched recursively for fields matching rule (1)
// and (2). Tags found within a struct are inherited by measures generated from
// sub-fields, they may also be overwritten.
//
func MakeMeasures(prefix string, value interface{}, tags ...Tag) []Measure {
if !TagsAreSorted(tags) {
SortTags(tags)
}
return makeMeasures(nil, prefix, reflect.ValueOf(value), tags...)
}
func makeMeasures(cache *measureCache, prefix string, value reflect.Value, tags ...Tag) []Measure {
return appendMeasures(nil, cache, prefix, value, tags...)
}
func appendMeasures(m []Measure, cache *measureCache, prefix string, v reflect.Value, tags ...Tag) []Measure {
var p reflect.Value
// The optimized routines for generating Measure values need to have the
// address of the value, which means it has to be addressable. In the event
// where it's not we have to make a copy of the value to be able to safely
// get a pointer.
switch {
case v.Kind() == reflect.Ptr:
p = v
v = v.Elem()
case v.CanAddr():
p = v.Addr()
default:
p = reflect.New(v.Type())
p.Elem().Set(v)
}
switch v.Kind() {
case reflect.Array, reflect.Slice:
for i, n := 0, v.Len(); i != n; i++ {
m = appendMeasures(m, cache, prefix, v.Index(i), tags...)
}
return m
}
var ptr = unsafe.Pointer(p.Pointer())
var typ = v.Type()
var mf []measureFuncs
var ok bool
if cache != nil {
mf, ok = cache.lookup(typ)
}
if !ok {
mf = makeMeasureFuncs(typ, prefix)
if cache != nil {
cache.set(typ, mf)
}
}
used := len(m)
free := cap(m) - used
need := len(mf)
if free < need {
m = append(make([]Measure, 0, used+need), m...)
}
m = m[:used+need]
for i := range mf {
m[used+i].set(ptr, mf[i], tags...)
}
return m
}
func (m *Measure) set(ptr unsafe.Pointer, mf measureFuncs, tags ...Tag) {
m.Name = mf.name
if cap(m.Fields) < len(mf.fields) {
m.Fields = make([]Field, len(mf.fields))
} else {
m.Fields = m.Fields[:len(mf.fields)]
}
for i := range m.Fields {
m.Fields[i] = mf.fields[i](ptr)
}
n0 := cap(m.Tags)
n1 := len(mf.tags)
n2 := len(tags)
n3 := n1 + n2
if n0 < n3 {
m.Tags = make([]Tag, n3)
} else {
m.Tags = m.Tags[:n3]
}
i1 := 0
i2 := 0
for i := range m.Tags {
switch {
case i1 == n1:
m.Tags[i] = tags[i2]
i2++
case i2 == n2:
m.Tags[i] = mf.tags[i1](ptr)
i1++
default:
t1 := mf.tags[i1](ptr)
t2 := tags[i2]
if t1.Name < t2.Name {
m.Tags[i] = t1
i1++
} else {
m.Tags[i] = t2
i2++
}
}
}
}
func (m *Measure) reset() {
for i := range m.Fields {
m.Fields[i] = Field{}
}
for i := range m.Tags {
m.Tags[i] = Tag{}
}
m.Name = ""
m.Fields = m.Fields[:0]
m.Tags = m.Tags[:0]
}
type measureFuncs struct {
name string
fields []func(unsafe.Pointer) Field
tags []func(unsafe.Pointer) Tag
}
func makeMeasureFuncs(typ reflect.Type, prefix string) []measureFuncs {
return appendMeasureFuncs(nil, typ, prefix, nil, 0)
}
func appendMeasureFuncs(measures []measureFuncs, typ reflect.Type, name string, tags tagFuncMap, offset uintptr) []measureFuncs {
tags = tags.copy()
if typ.Kind() != reflect.Struct {
panic("measures can only be constructed from struct type but " + typ.String() + " was given")
}
for i, n := 0, typ.NumField(); i != n; i++ {
field := typ.Field(i)
if tag := field.Tag.Get("tag"); len(tag) != 0 {
switch field.Type {
case stringType:
sf := structField{typ: field.Type, off: offset + field.Offset}
tags[tag] = makeTagFunc(sf, tag)
default:
panic("unsupported value type found for metric tags of " + concat(name, tag) + ": " + field.Type.String())
}
}
}
mf := measureFuncs{name: name, tags: tags.funcs()}
for i, n := 0, typ.NumField(); i != n; i++ {
field := typ.Field(i)
metric := field.Tag.Get("metric")
switch field.Type.Kind() {
case reflect.Struct:
measures = appendMeasureFuncs(measures, field.Type, concat(name, metric), tags, offset+field.Offset)
default:
if len(metric) != 0 {
sf := structField{typ: field.Type, off: offset + field.Offset}
t := makeFieldType(field.Tag.Get("type"))
f := makeFieldFunc(sf, metric, t)
if f == nil {
panic("unsupported value type found for metric " + concat(name, metric) + ": " + field.Type.String())
}
mf.fields = append(mf.fields, f)
}
}
}
if len(mf.fields) != 0 {
measures = append(measures, mf)
}
return measures
}
func makeFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
switch sf.typ {
case boolType:
return makeBoolFieldFunc(sf, name, ftype)
case intType:
return makeIntFieldFunc(sf, name, ftype)
case int8Type:
return makeInt8FieldFunc(sf, name, ftype)
case int16Type:
return makeInt16FieldFunc(sf, name, ftype)
case int32Type:
return makeInt32FieldFunc(sf, name, ftype)
case int64Type:
return makeInt64FieldFunc(sf, name, ftype)
case uintType:
return makeUintFieldFunc(sf, name, ftype)
case uint8Type:
return makeUint8FieldFunc(sf, name, ftype)
case uint16Type:
return makeUint16FieldFunc(sf, name, ftype)
case uint32Type:
return makeUint32FieldFunc(sf, name, ftype)
case uint64Type:
return makeUint64FieldFunc(sf, name, ftype)
case uintptrType:
return makeUintptrFieldFunc(sf, name, ftype)
case float32Type:
return makeFloat32FieldFunc(sf, name, ftype)
case float64Type:
return makeFloat64FieldFunc(sf, name, ftype)
case durationType:
return makeDurationFieldFunc(sf, name, ftype)
default:
return nil
}
}
func makeBoolFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return boolValue(sf.bool(ptr)) })
}
func makeIntFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return intValue(sf.int(ptr)) })
}
func makeInt8FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return int8Value(sf.int8(ptr)) })
}
func makeInt16FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return int16Value(sf.int16(ptr)) })
}
func makeInt32FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return int32Value(sf.int32(ptr)) })
}
func makeInt64FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return int64Value(sf.int64(ptr)) })
}
func makeUintFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uintValue(sf.uint(ptr)) })
}
func makeUint8FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uint8Value(sf.uint8(ptr)) })
}
func makeUint16FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uint16Value(sf.uint16(ptr)) })
}
func makeUint32FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uint32Value(sf.uint32(ptr)) })
}
func makeUint64FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uint64Value(sf.uint64(ptr)) })
}
func makeUintptrFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return uintptrValue(sf.uintptr(ptr)) })
}
func makeFloat32FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return float32Value(sf.float32(ptr)) })
}
func makeFloat64FieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return float64Value(sf.float64(ptr)) })
}
func makeDurationFieldFunc(sf structField, name string, ftype FieldType) func(unsafe.Pointer) Field {
return makeAnyFieldFunc(name, ftype, func(ptr unsafe.Pointer) Value { return durationValue(sf.duration(ptr)) })
}
func makeAnyFieldFunc(name string, ftype FieldType, valueOf func(unsafe.Pointer) Value) func(unsafe.Pointer) Field {
return func(ptr unsafe.Pointer) Field {
f := Field{Name: name, Value: valueOf(ptr)}
f.setType(ftype)
return f
}
}
func makeFieldType(mtype string) FieldType {
switch mtype {
case "counter":
return Counter
case "gauge":
return Gauge
default:
return Histogram
}
}
type tagFuncMap map[string](func(unsafe.Pointer) Tag)
func (tags tagFuncMap) copy() tagFuncMap {
cpy := make(tagFuncMap, len(tags))
for name, fn := range tags {
cpy[name] = fn
}
return cpy
}
func (tags tagFuncMap) namedTagFuncs() []namedTagFunc {
namedTags := make([]namedTagFunc, 0, len(tags))
for name, fn := range tags {
namedTags = append(namedTags, namedTagFunc{name: name, fn: fn})
}
return namedTags
}
func (tags tagFuncMap) funcs() []func(unsafe.Pointer) Tag {
namedTags := tags.namedTagFuncs()
sort.Sort(tagFuncByName(namedTags))
fns := make([]func(unsafe.Pointer) Tag, len(namedTags))
for i, tag := range namedTags {
fns[i] = tag.fn
}
return fns
}
type namedTagFunc struct {
name string
fn func(unsafe.Pointer) Tag
}
func makeTagFunc(sf structField, name string) func(unsafe.Pointer) Tag {
return func(ptr unsafe.Pointer) Tag { return Tag{Name: name, Value: sf.string(ptr)} }
}
type tagFuncByName []namedTagFunc
func (t tagFuncByName) Len() int { return len(t) }
func (t tagFuncByName) Less(i int, j int) bool { return t[i].name < t[j].name }
func (t tagFuncByName) Swap(i int, j int) { t[i], t[j] = t[j], t[i] }
func concat(prefix string, suffix string) string {
if len(prefix) == 0 {
return suffix
}
if len(suffix) == 0 {
return prefix
}
return prefix + "." + suffix
}
type measuresBuffer struct {
measures []Measure
}
var measurePool = sync.Pool{
New: func() interface{} {
return &measuresBuffer{measures: make([]Measure, 0, 32)}
},
}
type measureCache struct {
cache unsafe.Pointer
}
func (c *measureCache) lookup(typ reflect.Type) ([]measureFuncs, bool) {
m := c.load()
if m == nil {
return nil, false
}
mf, ok := (*m)[typ]
return mf, ok
}
func (c *measureCache) set(typ reflect.Type, mf []measureFuncs) {
for {
m1 := c.load()
m2 := map[reflect.Type][]measureFuncs{typ: mf}
if m1 != nil {
for t, f := range *m1 {
m2[t] = f
}
}
if c.compareAndSwap(m1, &m2) {
break
}
}
}
func (c *measureCache) load() *map[reflect.Type][]measureFuncs {
return (*map[reflect.Type][]measureFuncs)(atomic.LoadPointer(&c.cache))
}
func (c *measureCache) compareAndSwap(old *map[reflect.Type][]measureFuncs, new *map[reflect.Type][]measureFuncs) bool {
return atomic.CompareAndSwapPointer(&c.cache,
unsafe.Pointer(old),
unsafe.Pointer(new),
)
}