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