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opentelemetry-go/sdk/trace/attributesmap.go
Punya Biswal ecf65d7968
Rename otel/label -> otel/attribute (#1541)
* Rename otel/label -> otel/attr

Leave the imported name alone, to avoid a large diff and conflicts

* Better import comment

* Update CHANGELOG.md

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>

* otel/attr -> otel/attribute

* Missed the changelog entry

* Get rid of import renaming

* Merge remaining conflicts

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
Co-authored-by: Anthony Mirabella <a9@aneurysm9.com>
2021-02-18 12:59:37 -05:00

92 lines
2.6 KiB
Go

// Copyright The OpenTelemetry 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 trace // import "go.opentelemetry.io/otel/sdk/trace"
import (
"container/list"
"go.opentelemetry.io/otel/attribute"
)
// attributesMap is a capped map of attributes, holding the most recent attributes.
// Eviction is done via a LRU method, the oldest entry is removed to create room for a new entry.
// Updates are allowed and they refresh the usage of the key.
//
// This is based from https://github.com/hashicorp/golang-lru/blob/master/simplelru/lru.go
// With a subset of the its operations and specific for holding attribute.KeyValue
type attributesMap struct {
attributes map[attribute.Key]*list.Element
evictList *list.List
droppedCount int
capacity int
}
func newAttributesMap(capacity int) *attributesMap {
lm := &attributesMap{
attributes: make(map[attribute.Key]*list.Element),
evictList: list.New(),
capacity: capacity,
}
return lm
}
func (am *attributesMap) add(kv attribute.KeyValue) {
// Check for existing item
if ent, ok := am.attributes[kv.Key]; ok {
am.evictList.MoveToFront(ent)
ent.Value = &kv
return
}
// Add new item
entry := am.evictList.PushFront(&kv)
am.attributes[kv.Key] = entry
// Verify size not exceeded
if am.evictList.Len() > am.capacity {
am.removeOldest()
am.droppedCount++
}
}
// toKeyValue copies the attributesMap into a slice of attribute.KeyValue and
// returns it. If the map is empty, a nil is returned.
// TODO: Is it more efficient to return a pointer to the slice?
func (am *attributesMap) toKeyValue() []attribute.KeyValue {
len := am.evictList.Len()
if len == 0 {
return nil
}
attributes := make([]attribute.KeyValue, 0, len)
for ent := am.evictList.Back(); ent != nil; ent = ent.Prev() {
if value, ok := ent.Value.(*attribute.KeyValue); ok {
attributes = append(attributes, *value)
}
}
return attributes
}
// removeOldest removes the oldest item from the cache.
func (am *attributesMap) removeOldest() {
ent := am.evictList.Back()
if ent != nil {
am.evictList.Remove(ent)
kv := ent.Value.(*attribute.KeyValue)
delete(am.attributes, kv.Key)
}
}