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From https://github.com/open-telemetry/opentelemetry-go-contrib/pull/5654#discussion_r1617971674 Constructing a view requires an `Instrument` to be constructed. Given `NewView` will not return an error directly when an empty instrument is passed, it may be ideal for users to check this prior to making the call. Instead of having all use-cases copy this code, export it so they can just call the method.
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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