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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package metric // import "go.opentelemetry.io/otel/sdk/metric"
import (
"context"
"fmt"
"sync"
"go.opentelemetry.io/otel"
"go.opentelemetry.io/otel/sdk/resource"
)
// config contains configuration options for a MeterProvider.
type config struct {
res *resource.Resource
readers []Reader
views []View
}
// readerSignals returns a force-flush and shutdown function for a
// MeterProvider to call in their respective options. All Readers c contains
// will have their force-flush and shutdown methods unified into returned
// single functions.
func (c config) readerSignals() (forceFlush, shutdown func(context.Context) error) {
var fFuncs, sFuncs []func(context.Context) error
for _, r := range c.readers {
sFuncs = append(sFuncs, r.Shutdown)
if f, ok := r.(interface{ ForceFlush(context.Context) error }); ok {
fFuncs = append(fFuncs, f.ForceFlush)
}
}
return unify(fFuncs), unifyShutdown(sFuncs)
}
// unify unifies calling all of funcs into a single function call. All errors
// returned from calls to funcs will be unify into a single error return
// value.
func unify(funcs []func(context.Context) error) func(context.Context) error {
return func(ctx context.Context) error {
var errs []error
for _, f := range funcs {
if err := f(ctx); err != nil {
errs = append(errs, err)
}
}
return unifyErrors(errs)
}
}
// unifyErrors combines multiple errors into a single error.
func unifyErrors(errs []error) error {
switch len(errs) {
case 0:
return nil
case 1:
return errs[0]
default:
return fmt.Errorf("%v", errs)
}
}
// unifyShutdown unifies calling all of funcs once for a shutdown. If called
// more than once, an ErrReaderShutdown error is returned.
func unifyShutdown(funcs []func(context.Context) error) func(context.Context) error {
f := unify(funcs)
var once sync.Once
return func(ctx context.Context) error {
err := ErrReaderShutdown
once.Do(func() { err = f(ctx) })
return err
}
}
// newConfig returns a config configured with options.
func newConfig(options []Option) config {
conf := config{res: resource.Default()}
for _, o := range options {
conf = o.apply(conf)
}
return conf
}
// Option applies a configuration option value to a MeterProvider.
type Option interface {
apply(config) config
}
// optionFunc applies a set of options to a config.
type optionFunc func(config) config
// apply returns a config with option(s) applied.
func (o optionFunc) apply(conf config) config {
return o(conf)
}
// WithResource associates a Resource with a MeterProvider. This Resource
// represents the entity producing telemetry and is associated with all Meters
// the MeterProvider will create.
//
// By default, if this Option is not used, the default Resource from the
// go.opentelemetry.io/otel/sdk/resource package will be used.
func WithResource(res *resource.Resource) Option {
return optionFunc(func(conf config) config {
var err error
conf.res, err = resource.Merge(resource.Environment(), res)
if err != nil {
otel.Handle(err)
}
return conf
})
}
// WithReader associates Reader r with a MeterProvider.
//
// By default, if this option is not used, the MeterProvider will perform no
// operations; no data will be exported without a Reader.
func WithReader(r Reader) Option {
return optionFunc(func(cfg config) config {
if r == nil {
return cfg
}
cfg.readers = append(cfg.readers, r)
return cfg
})
}
// WithView associates views with a MeterProvider.
//
// Views are appended to existing ones in a MeterProvider if this option is
// used multiple times.
//
// By default, if this option is not used, the MeterProvider will use the
// default view.
func WithView(views ...View) Option {
return optionFunc(func(cfg config) config {
cfg.views = append(cfg.views, views...)
return cfg
})
}
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