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- // Copyright (c) 2017 Uber Technologies, Inc.
- //
- // 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.
- package metrics
- import (
- "fmt"
- "reflect"
- "strconv"
- "strings"
- )
- // MustInit initializes the passed in metrics and initializes its fields using the passed in factory.
- //
- // It uses reflection to initialize a struct containing metrics fields
- // by assigning new Counter/Gauge/Timer values with the metric name retrieved
- // from the `metric` tag and stats tags retrieved from the `tags` tag.
- //
- // Note: all fields of the struct must be exported, have a `metric` tag, and be
- // of type Counter or Gauge or Timer.
- //
- // Errors during Init lead to a panic.
- func MustInit(metrics interface{}, factory Factory, globalTags map[string]string) {
- if err := Init(metrics, factory, globalTags); err != nil {
- panic(err.Error())
- }
- }
- // Init does the same as MustInit, but returns an error instead of
- // panicking.
- func Init(m interface{}, factory Factory, globalTags map[string]string) error {
- // Allow user to opt out of reporting metrics by passing in nil.
- if factory == nil {
- factory = NullFactory
- }
- counterPtrType := reflect.TypeOf((*Counter)(nil)).Elem()
- gaugePtrType := reflect.TypeOf((*Gauge)(nil)).Elem()
- timerPtrType := reflect.TypeOf((*Timer)(nil)).Elem()
- histogramPtrType := reflect.TypeOf((*Histogram)(nil)).Elem()
- v := reflect.ValueOf(m).Elem()
- t := v.Type()
- for i := 0; i < t.NumField(); i++ {
- tags := make(map[string]string)
- for k, v := range globalTags {
- tags[k] = v
- }
- var buckets []float64
- field := t.Field(i)
- metric := field.Tag.Get("metric")
- if metric == "" {
- return fmt.Errorf("Field %s is missing a tag 'metric'", field.Name)
- }
- if tagString := field.Tag.Get("tags"); tagString != "" {
- tagPairs := strings.Split(tagString, ",")
- for _, tagPair := range tagPairs {
- tag := strings.Split(tagPair, "=")
- if len(tag) != 2 {
- return fmt.Errorf(
- "Field [%s]: Tag [%s] is not of the form key=value in 'tags' string [%s]",
- field.Name, tagPair, tagString)
- }
- tags[tag[0]] = tag[1]
- }
- }
- if bucketString := field.Tag.Get("buckets"); bucketString != "" {
- if field.Type.AssignableTo(timerPtrType) {
- // TODO: Parse timer duration buckets
- return fmt.Errorf(
- "Field [%s]: Buckets are not currently initialized for timer metrics",
- field.Name)
- } else if field.Type.AssignableTo(histogramPtrType) {
- bucketValues := strings.Split(bucketString, ",")
- for _, bucket := range bucketValues {
- b, err := strconv.ParseFloat(bucket, 64)
- if err != nil {
- return fmt.Errorf(
- "Field [%s]: Bucket [%s] could not be converted to float64 in 'buckets' string [%s]",
- field.Name, bucket, bucketString)
- }
- buckets = append(buckets, b)
- }
- } else {
- return fmt.Errorf(
- "Field [%s]: Buckets should only be defined for Timer and Histogram metric types",
- field.Name)
- }
- }
- help := field.Tag.Get("help")
- var obj interface{}
- if field.Type.AssignableTo(counterPtrType) {
- obj = factory.Counter(Options{
- Name: metric,
- Tags: tags,
- Help: help,
- })
- } else if field.Type.AssignableTo(gaugePtrType) {
- obj = factory.Gauge(Options{
- Name: metric,
- Tags: tags,
- Help: help,
- })
- } else if field.Type.AssignableTo(timerPtrType) {
- // TODO: Add buckets once parsed (see TODO above)
- obj = factory.Timer(TimerOptions{
- Name: metric,
- Tags: tags,
- Help: help,
- })
- } else if field.Type.AssignableTo(histogramPtrType) {
- obj = factory.Histogram(HistogramOptions{
- Name: metric,
- Tags: tags,
- Help: help,
- Buckets: buckets,
- })
- } else {
- return fmt.Errorf(
- "Field %s is not a pointer to timer, gauge, or counter",
- field.Name)
- }
- v.Field(i).Set(reflect.ValueOf(obj))
- }
- return nil
- }
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