Source: collector.go in package go.opencensus.io/stats/view

Copyright 2017, OpenCensus Authors 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 view

import (
	"sort"
	"time"

	"go.opencensus.io/internal/tagencoding"
	"go.opencensus.io/tag"
)

signatures holds the aggregations values for each unique tag signature (values for all keys) to its aggregator.

Aggregation is the description of the aggregation to perform for this view.

	a *Aggregation
}

func (c *collector) addSample(s string, v float64, attachments map[string]interface{}, t time.Time) {
	aggregator, ok := c.signatures[s]
	if !ok {
		aggregator = c.a.newData()
		c.signatures[s] = aggregator
	}
	aggregator.addSample(v, attachments, t)
}

collectRows returns a snapshot of the collected Row values.

func (c *collector) collectedRows(keys []tag.Key) []*Row {
	rows := make([]*Row, 0, len(c.signatures))
	for sig, aggregator := range c.signatures {
		tags := decodeTags([]byte(sig), keys)
		row := &Row{Tags: tags, Data: aggregator.clone()}
		rows = append(rows, row)
	}
	return rows
}

func (c *collector) clearRows() {
	c.signatures = make(map[string]AggregationData)
}

encodeWithKeys encodes the map by using values only associated with the keys provided.

func encodeWithKeys(m *tag.Map, keys []tag.Key) []byte {
	vb := &tagencoding.Values{
		Buffer: make([]byte, len(keys)),
	}
	for _, k := range keys {
		v, _ := m.Value(k)
		vb.WriteValue([]byte(v))
	}
	return vb.Bytes()
}

decodeTags decodes tags from the buffer and orders them by the keys.

func decodeTags(buf []byte, keys []tag.Key) []tag.Tag {
	vb := &tagencoding.Values{Buffer: buf}
	var tags []tag.Tag
	for _, k := range keys {
		v := vb.ReadValue()
		if v != nil {
			tags = append(tags, tag.Tag{Key: k, Value: string(v)})
		}
	}
	vb.ReadIndex = 0
	sort.Slice(tags, func(i, j int) bool { return tags[i].Key.Name() < tags[j].Key.Name() })
	return tags