86 lines
2.8 KiB
Go
86 lines
2.8 KiB
Go
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// Copyright (c) 2017 Uber Technologies, Inc.
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//
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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 metrics
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import (
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"fmt"
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"reflect"
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"strings"
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)
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// Init initializes the passed in metrics and initializes its fields using the passed in factory.
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func Init(metrics interface{}, factory Factory, globalTags map[string]string) {
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if err := initMetrics(metrics, factory, globalTags); err != nil {
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panic(err.Error())
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}
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}
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// initMetrics uses reflection to initialize a struct containing metrics fields
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// by assigning new Counter/Gauge/Timer values with the metric name retrieved
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// from the `metric` tag and stats tags retrieved from the `tags` tag.
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//
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// Note: all fields of the struct must be exported, have a `metric` tag, and be
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// of type Counter or Gauge or Timer.
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func initMetrics(m interface{}, factory Factory, globalTags map[string]string) error {
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// Allow user to opt out of reporting metrics by passing in nil.
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if factory == nil {
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factory = NullFactory
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}
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counterPtrType := reflect.TypeOf((*Counter)(nil)).Elem()
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gaugePtrType := reflect.TypeOf((*Gauge)(nil)).Elem()
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timerPtrType := reflect.TypeOf((*Timer)(nil)).Elem()
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v := reflect.ValueOf(m).Elem()
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t := v.Type()
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for i := 0; i < t.NumField(); i++ {
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tags := make(map[string]string)
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for k, v := range globalTags {
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tags[k] = v
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}
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field := t.Field(i)
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metric := field.Tag.Get("metric")
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if metric == "" {
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return fmt.Errorf("Field %s is missing a tag 'metric'", field.Name)
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}
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if tagString := field.Tag.Get("tags"); tagString != "" {
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tagPairs := strings.Split(tagString, ",")
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for _, tagPair := range tagPairs {
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tag := strings.Split(tagPair, "=")
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if len(tag) != 2 {
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return fmt.Errorf(
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"Field [%s]: Tag [%s] is not of the form key=value in 'tags' string [%s]",
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field.Name, tagPair, tagString)
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}
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tags[tag[0]] = tag[1]
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}
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}
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var obj interface{}
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if field.Type.AssignableTo(counterPtrType) {
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obj = factory.Counter(metric, tags)
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} else if field.Type.AssignableTo(gaugePtrType) {
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obj = factory.Gauge(metric, tags)
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} else if field.Type.AssignableTo(timerPtrType) {
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obj = factory.Timer(metric, tags)
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} else {
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return fmt.Errorf(
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"Field %s is not a pointer to timer, gauge, or counter",
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field.Name)
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}
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v.Field(i).Set(reflect.ValueOf(obj))
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}
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return nil
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}
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