mirror of
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82 lines
2.8 KiB
Go
82 lines
2.8 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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"os"
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"runtime"
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"slices"
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"go.opentelemetry.io/otel/sdk/metric/internal/exemplar"
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"go.opentelemetry.io/otel/sdk/metric/internal/x"
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)
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// reservoirFunc returns the appropriately configured exemplar reservoir
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// creation func based on the passed InstrumentKind and user defined
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// environment variables.
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//
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// Note: This will only return non-nil values when the experimental exemplar
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// feature is enabled and the OTEL_METRICS_EXEMPLAR_FILTER environment variable
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// is not set to always_off.
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func reservoirFunc[N int64 | float64](agg Aggregation) func() exemplar.FilteredReservoir[N] {
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if !x.Exemplars.Enabled() {
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return nil
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}
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// https://github.com/open-telemetry/opentelemetry-specification/blob/d4b241f451674e8f611bb589477680341006ad2b/specification/configuration/sdk-environment-variables.md#exemplar
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const filterEnvKey = "OTEL_METRICS_EXEMPLAR_FILTER"
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var filter exemplar.Filter
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switch os.Getenv(filterEnvKey) {
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case "always_on":
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filter = exemplar.AlwaysOnFilter
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case "always_off":
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return exemplar.Drop
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case "trace_based":
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fallthrough
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default:
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filter = exemplar.SampledFilter
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}
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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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cp := slices.Clone(a.Boundaries)
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return func() exemplar.FilteredReservoir[N] {
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bounds := cp
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return exemplar.NewFilteredReservoir[N](filter, exemplar.Histogram(bounds))
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}
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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 = int(a.MaxSize)
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if n > 20 {
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n = 20
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}
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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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n = runtime.NumCPU()
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if n < 1 {
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// Should never be the case, but be defensive.
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n = 1
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}
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}
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return func() exemplar.FilteredReservoir[N] {
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return exemplar.NewFilteredReservoir[N](filter, exemplar.FixedSize(n))
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}
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}
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