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opentelemetry-go/sdk/metric/cache.go
Tyler Yahn f78f72d66c
Merge instrument cache to inserter (#3724)
* Merge instrument cache to inserter

The current pipeline resolution path will only add the resolved
aggregators to the pipeline when it creates one (cache miss). It will
not add it if there is a cache hit. This means (since we cache
instruments at the meter level, not the pipeline level) the first reader
in a multiple-reader setup is the only one that will collect data for
that aggregator. All other readers will have a cache hit and nothing is
added to the pipeline. This is causing #3720.

This resolves #3720 by moving the instrument caching into the inserter.
This means aggregators are cached at the reader level, not the meter.

* Rename aggCV to aggVal

---------

Co-authored-by: Chester Cheung <cheung.zhy.csu@gmail.com>
2023-02-21 08:07:37 -08:00

55 lines
1.5 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 metric // import "go.opentelemetry.io/otel/sdk/metric"
import (
"sync"
)
// cache is a locking storage used to quickly return already computed values.
//
// The zero value of a cache is empty and ready to use.
//
// A cache must not be copied after first use.
//
// All methods of a cache are safe to call concurrently.
type cache[K comparable, V any] struct {
sync.Mutex
data map[K]V
}
// Lookup returns the value stored in the cache with the accociated key if it
// exists. Otherwise, f is called and its returned value is set in the cache
// for key and returned.
//
// Lookup is safe to call concurrently. It will hold the cache lock, so f
// should not block excessively.
func (c *cache[K, V]) Lookup(key K, f func() V) V {
c.Lock()
defer c.Unlock()
if c.data == nil {
val := f()
c.data = map[K]V{key: val}
return val
}
if v, ok := c.data[key]; ok {
return v
}
val := f()
c.data[key] = val
return val
}