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6e2f72f698
Part of https://github.com/open-telemetry/opentelemetry-go/issues/5249. Addresses https://github.com/open-telemetry/opentelemetry-go/issues/5249#issuecomment-2088725450 This removes handling of the `OTEL_GO_X_EXEMPLAR` environment variable. Instead of changing the default for the existing environment variable to enable it by default, i'm just removing it entirely. Users can still disable the feature by setting the filter to always_off. Since we will continue to support that configuration, it seems better to direct users there, rather than give them a temporary equivalent.
78 lines
2.8 KiB
Go
78 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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)
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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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// 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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