/
counter.go
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/
counter.go
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// Copyright 2019, 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 counter // import "go.opentelemetry.io/otel/sdk/metric/aggregator/counter"
import (
"context"
"go.opentelemetry.io/otel/api/core"
export "go.opentelemetry.io/otel/sdk/export/metric"
"go.opentelemetry.io/otel/sdk/export/metric/aggregator"
)
// Aggregator aggregates counter events.
type Aggregator struct {
// current holds current increments to this counter record
// current needs to be aligned for 64-bit atomic operations.
current core.Number
// checkpoint is a temporary used during Checkpoint()
// checkpoint needs to be aligned for 64-bit atomic operations.
checkpoint core.Number
}
var _ export.Aggregator = &Aggregator{}
var _ aggregator.Sum = &Aggregator{}
// New returns a new counter aggregator implemented by atomic
// operations. This aggregator implements the aggregator.Sum
// export interface.
func New() *Aggregator {
return &Aggregator{}
}
// Sum returns the last-checkpointed sum. This will never return an
// error.
func (c *Aggregator) Sum() (core.Number, error) {
return c.checkpoint, nil
}
// Checkpoint atomically saves the current value and resets the
// current sum to zero.
func (c *Aggregator) Checkpoint(ctx context.Context, _ *export.Descriptor) {
c.checkpoint = c.current.SwapNumberAtomic(core.Number(0))
}
// Update atomically adds to the current value.
func (c *Aggregator) Update(_ context.Context, number core.Number, desc *export.Descriptor) error {
c.current.AddNumberAtomic(desc.NumberKind(), number)
return nil
}
// Merge combines two counters by adding their sums.
func (c *Aggregator) Merge(oa export.Aggregator, desc *export.Descriptor) error {
o, _ := oa.(*Aggregator)
if o == nil {
return aggregator.NewInconsistentMergeError(c, oa)
}
c.checkpoint.AddNumber(desc.NumberKind(), o.checkpoint)
return nil
}