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This PR changes `DefaultExemplarReservoirProviderSelector` in `go.opentelemetry.io/otel/sdk/metric` to use `runtime.GOMAXPROCS(0)` instead of `runtime.NumCPU()` for the `FixedSizeReservoirProvider` default size. **Motivation** The [runtime.NumCPU](https://pkg.go.dev/runtime#NumCPU) returns the number of logical CPUs usable by the current process. In Kubernetes, the method will return the total number of cores on the node, not the actual number of cores available to the container. Since it is common practice to allocate only a small fraction of the total CPU on a node to a container, the current implementation may result in an excessive `FixedSizeReservoir` size, which in turn negatively impacts the resources consumed. --------- Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com> Co-authored-by: Tyler Yahn <codingalias@gmail.com>
78 lines
3.3 KiB
Go
78 lines
3.3 KiB
Go
// Copyright The OpenTelemetry Authors
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// SPDX-License-Identifier: Apache-2.0
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package metric // import "go.opentelemetry.io/otel/sdk/metric"
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import (
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"runtime"
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"go.opentelemetry.io/otel/attribute"
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"go.opentelemetry.io/otel/sdk/metric/exemplar"
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"go.opentelemetry.io/otel/sdk/metric/internal/aggregate"
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)
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// ExemplarReservoirProviderSelector selects the
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// [exemplar.ReservoirProvider] to use
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// based on the [Aggregation] of the metric.
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type ExemplarReservoirProviderSelector func(Aggregation) exemplar.ReservoirProvider
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// reservoirFunc returns the appropriately configured exemplar reservoir
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// creation func based on the passed InstrumentKind and filter configuration.
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func reservoirFunc[N int64 | float64](
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provider exemplar.ReservoirProvider,
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filter exemplar.Filter,
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) func(attribute.Set) aggregate.FilteredExemplarReservoir[N] {
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return func(attrs attribute.Set) aggregate.FilteredExemplarReservoir[N] {
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return aggregate.NewFilteredExemplarReservoir[N](filter, provider(attrs))
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}
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}
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// DefaultExemplarReservoirProviderSelector returns the default
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// [exemplar.ReservoirProvider] for the
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// provided [Aggregation].
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//
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// For explicit bucket histograms with more than 1 bucket, it uses the
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// [exemplar.HistogramReservoirProvider].
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// For exponential histograms, it uses the
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// [exemplar.FixedSizeReservoirProvider]
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// with a size of min(20, max_buckets).
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// For all other aggregations, it uses the
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// [exemplar.FixedSizeReservoirProvider]
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// with a size equal to the number of CPUs.
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//
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// Exemplar default reservoirs MAY change in a minor version bump. No
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// guarantees are made on the shape or statistical properties of returned
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// exemplars.
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func DefaultExemplarReservoirProviderSelector(agg Aggregation) exemplar.ReservoirProvider {
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// https://github.com/open-telemetry/opentelemetry-specification/blob/d4b241f451674e8f611bb589477680341006ad2b/specification/metrics/sdk.md#exemplar-defaults
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// Explicit bucket histogram aggregation with more than 1 bucket will
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// use AlignedHistogramBucketExemplarReservoir.
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a, ok := agg.(AggregationExplicitBucketHistogram)
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if ok && len(a.Boundaries) > 0 {
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return exemplar.HistogramReservoirProvider(a.Boundaries)
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}
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var n int
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if a, ok := agg.(AggregationBase2ExponentialHistogram); ok {
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// Base2 Exponential Histogram Aggregation SHOULD use a
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// SimpleFixedSizeExemplarReservoir with a reservoir equal to the
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// smaller of the maximum number of buckets configured on the
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// aggregation or twenty (e.g. min(20, max_buckets)).
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n = min(int(a.MaxSize), 20)
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} else {
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// https://github.com/open-telemetry/opentelemetry-specification/blob/e94af89e3d0c01de30127a0f423e912f6cda7bed/specification/metrics/sdk.md#simplefixedsizeexemplarreservoir
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// This Exemplar reservoir MAY take a configuration parameter for
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// the size of the reservoir. If no size configuration is
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// provided, the default size MAY be the number of possible
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// concurrent threads (e.g. number of CPUs) to help reduce
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// contention. Otherwise, a default size of 1 SHOULD be used.
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//
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// Use runtime.GOMAXPROCS instead of runtime.NumCPU to support
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// containerized environments that may have less than the total number
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// of logical CPUs available on the local machine allocated to it.
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n = max(runtime.GOMAXPROCS(0), 1)
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}
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return exemplar.FixedSizeReservoirProvider(n)
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}
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