聊聊dapr的metrics_utils

序

本文主要研究一下dapr的metrics_utils

NewMeasureView

dapr/pkg/diagnostics/utils/metrics_utils.go

// NewMeasureView creates opencensus View instance using stats.Measure
func NewMeasureView(measure stats.Measure, keys []tag.Key, aggregation *view.Aggregation) *view.View {
	return &view.View{
		Name:        measure.Name(),
		Description: measure.Description(),
		Measure:     measure,
		TagKeys:     keys,
		Aggregation: aggregation,
	}
}

NewMeasureView根據measure、tag、aggregation來創建view

WithTags

dapr/pkg/diagnostics/utils/metrics_utils.go

// WithTags converts tag key and value pairs to tag.Mutator array.
// WithTags(key1, value1, key2, value2) returns
// []tag.Mutator{tag.Upsert(key1, value1), tag.Upsert(key2, value2)}
func WithTags(opts ...interface{}) []tag.Mutator {
	tagMutators := []tag.Mutator{}
	for i := 0; i < len(opts)-1; i += 2 {
		key, ok := opts[i].(tag.Key)
		if !ok {
			break
		}
		value, ok := opts[i+1].(string)
		if !ok {
			break
		}
		// skip if value is empty
		if value != "" {
			tagMutators = append(tagMutators, tag.Upsert(key, value))
		}
	}
	return tagMutators
}

WithTags方法支持變長的tag.Key類型，支持將tag.Key轉換爲tag.Mutator

AddTagKeyToCtx

dapr/pkg/diagnostics/utils/metrics_utils.go

// AddTagKeyToCtx assigns opencensus tag key value to context
func AddTagKeyToCtx(ctx context.Context, key tag.Key, value string) context.Context {
	// return if value is not given
	if value == "" {
		return ctx
	}

	newCtx, err := tag.New(ctx, tag.Upsert(key, value))
	if err != nil {
		// return original if adding tagkey is failed.
		return ctx
	}

	return newCtx
}

AddTagKeyToCtx方法將key和value添加新的context中

AddNewTagKey

dapr/pkg/diagnostics/utils/metrics_utils.go

// AddNewTagKey adds new tag keys to existing view
func AddNewTagKey(views []*view.View, key *tag.Key) []*view.View {
	for _, v := range views {
		v.TagKeys = append(v.TagKeys, *key)
	}

	return views
}

AddNewTagKey方法遍歷views將指定key追加到view的TagKeys中

實例

dapr/pkg/diagnostics/utils/metrics_utils_test.go

func TestWithTags(t *testing.T) {
	t.Run("one tag", func(t *testing.T) {
		appKey := tag.MustNewKey("app_id")
		mutators := WithTags(appKey, "test")
		assert.Equal(t, 1, len(mutators))
	})

	t.Run("two tags", func(t *testing.T) {
		appKey := tag.MustNewKey("app_id")
		operationKey := tag.MustNewKey("operation")
		mutators := WithTags(appKey, "test", operationKey, "op")
		assert.Equal(t, 2, len(mutators))
	})

	t.Run("three tags", func(t *testing.T) {
		appKey := tag.MustNewKey("app_id")
		operationKey := tag.MustNewKey("operation")
		methodKey := tag.MustNewKey("method")
		mutators := WithTags(appKey, "test", operationKey, "op", methodKey, "method")
		assert.Equal(t, 3, len(mutators))
	})

	t.Run("two tags with wrong value type", func(t *testing.T) {
		appKey := tag.MustNewKey("app_id")
		operationKey := tag.MustNewKey("operation")
		mutators := WithTags(appKey, "test", operationKey, 1)
		assert.Equal(t, 1, len(mutators))
	})

	t.Run("skip empty value key", func(t *testing.T) {
		appKey := tag.MustNewKey("app_id")
		operationKey := tag.MustNewKey("operation")
		methodKey := tag.MustNewKey("method")
		mutators := WithTags(appKey, "", operationKey, "op", methodKey, "method")
		assert.Equal(t, 2, len(mutators))
	})
}

小結

dapr的metrics_utils基於opencensus的stats及tag提供了NewMeasureView、WithTags、AddTagKeyToCtx、AddNewTagKey方法。

doc

• dapr