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Delay evaluation of resource.Default to first call (#2371)

* change resource.Default to be evaluated on first call, rather than on import

* guard defaultResource creation with sync.Once, fallback to emtpyResource

* update CHANGELOG

Co-authored-by: Tyler Yahn <MrAlias@users.noreply.github.com>
This commit is contained in:
Brendan Roy 2021-11-16 03:46:11 +11:00 committed by GitHub
parent 2fa7bce696
commit 47203fa36b
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 22 additions and 18 deletions

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@ -19,6 +19,7 @@ This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.htm
- The following struct types moved and are replaced with type aliases, since they are exposed to the user: `Observation`, `Measurement`.
- The No-op implementations of sync and async instruments are no longer exported, new functions `sdkapi.NewNoopAsyncInstrument()` and `sdkapi.NewNoopSyncInstrument()` are provided instead. (#2271)
- Update the SDK `BatchSpanProcessor` to export all queued spans when `ForceFlush` is called. (#2080, #2335)
- Change `resource.Default` to be evaluated the first time it is called, rather than on import. This allows the caller the option to update `OTEL_RESOURCE_ATTRIBUTES` first, such as with `os.Setenv`. (#2371)
### Added

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@ -18,6 +18,7 @@ import (
"context"
"errors"
"fmt"
"sync"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/attribute"
@ -36,26 +37,12 @@ type Resource struct {
}
var (
emptyResource Resource
defaultResource = func(r *Resource, err error) *Resource {
if err != nil {
otel.Handle(err)
}
return r
}(
Detect(
context.Background(),
defaultServiceNameDetector{},
fromEnv{},
telemetrySDK{},
),
)
emptyResource Resource
defaultResource *Resource
defaultResourceOnce sync.Once
)
var (
errMergeConflictSchemaURL = errors.New("cannot merge resource due to conflicting Schema URL")
)
var errMergeConflictSchemaURL = errors.New("cannot merge resource due to conflicting Schema URL")
// New returns a Resource combined from the user-provided detectors.
func New(ctx context.Context, opts ...Option) (*Resource, error) {
@ -211,6 +198,22 @@ func Empty() *Resource {
// Default returns an instance of Resource with a default
// "service.name" and OpenTelemetrySDK attributes.
func Default() *Resource {
defaultResourceOnce.Do(func() {
var err error
defaultResource, err = Detect(
context.Background(),
defaultServiceNameDetector{},
fromEnv{},
telemetrySDK{},
)
if err != nil {
otel.Handle(err)
}
// If Detect did not return a valid resource, fall back to emptyResource.
if defaultResource == nil {
defaultResource = &emptyResource
}
})
return defaultResource
}