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118 lines
3.5 KiB
Go
118 lines
3.5 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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"errors"
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"regexp"
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"strings"
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"go.opentelemetry.io/otel/internal/global"
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)
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var (
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errMultiInst = errors.New("name replacement for multiple instruments")
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errEmptyView = errors.New("no criteria provided for view")
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emptyView = func(Instrument) (Stream, bool) { return Stream{}, false }
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)
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// View is an override to the default behavior of the SDK. It defines how data
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// should be collected for certain instruments. It returns true and the exact
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// Stream to use for matching Instruments. Otherwise, if the view does not
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// match, false is returned.
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type View func(Instrument) (Stream, bool)
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// NewView returns a View that applies the Stream mask for all instruments that
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// match criteria. The returned View will only apply mask if all non-zero-value
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// fields of criteria match the corresponding Instrument passed to the view. If
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// no criteria are provided, all field of criteria are their zero-values, a
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// view that matches no instruments is returned. If you need to match a
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// zero-value field, create a View directly.
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//
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// The Name field of criteria supports wildcard pattern matching. The "*"
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// wildcard is recognized as matching zero or more characters, and "?" is
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// recognized as matching exactly one character. For example, a pattern of "*"
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// matches all instrument names.
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//
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// The Stream mask only applies updates for non-zero-value fields. By default,
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// the Instrument the View matches against will be use for the Name,
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// Description, and Unit of the returned Stream and no Aggregation or
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// AttributeFilter are set. All non-zero-value fields of mask are used instead
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// of the default. If you need to zero out an Stream field returned from a
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// View, create a View directly.
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func NewView(criteria Instrument, mask Stream) View {
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if criteria.IsEmpty() {
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global.Error(
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errEmptyView, "dropping view",
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"mask", mask,
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)
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return emptyView
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}
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var matchFunc func(Instrument) bool
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if strings.ContainsAny(criteria.Name, "*?") {
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if mask.Name != "" {
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global.Error(
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errMultiInst, "dropping view",
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"criteria", criteria,
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"mask", mask,
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)
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return emptyView
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}
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// Handle branching here in NewView instead of criteria.matches so
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// criteria.matches remains inlinable for the simple case.
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pattern := regexp.QuoteMeta(criteria.Name)
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pattern = "^" + pattern + "$"
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pattern = strings.ReplaceAll(pattern, `\?`, ".")
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pattern = strings.ReplaceAll(pattern, `\*`, ".*")
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re := regexp.MustCompile(pattern)
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matchFunc = func(i Instrument) bool {
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return re.MatchString(i.Name) &&
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criteria.matchesDescription(i) &&
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criteria.matchesKind(i) &&
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criteria.matchesUnit(i) &&
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criteria.matchesScope(i)
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}
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} else {
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matchFunc = criteria.matches
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}
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var agg Aggregation
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if mask.Aggregation != nil {
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agg = mask.Aggregation.copy()
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if err := agg.err(); err != nil {
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global.Error(
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err, "not using aggregation with view",
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"criteria", criteria,
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"mask", mask,
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)
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agg = nil
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}
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}
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return func(i Instrument) (Stream, bool) {
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if matchFunc(i) {
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return Stream{
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Name: nonZero(mask.Name, i.Name),
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Description: nonZero(mask.Description, i.Description),
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Unit: nonZero(mask.Unit, i.Unit),
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Aggregation: agg,
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AttributeFilter: mask.AttributeFilter,
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}, true
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}
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return Stream{}, false
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}
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}
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// nonZero returns v if it is non-zero-valued, otherwise alt.
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func nonZero[T comparable](v, alt T) T {
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var zero T
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if v != zero {
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return v
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}
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return alt
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}
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