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opentelemetry-go/global/handler.go

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// Copyright The OpenTelemetry Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package global
import (
"log"
"os"
"sync"
"sync/atomic"
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"go.opentelemetry.io/otel"
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)
var (
// globalErrorHandler provides an ErrorHandler that can be used
// throughout an OpenTelemetry instrumented project. When a user
// specified ErrorHandler is registered (`SetErrorHandler`) all calls to
// `Handle` and will be delegated to the registered ErrorHandler.
globalErrorHandler = &loggingErrorHandler{
l: log.New(os.Stderr, "", log.LstdFlags),
}
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// delegateErrorHandlerOnce ensures that a user provided ErrorHandler is
// only ever registered once.
delegateErrorHandlerOnce sync.Once
// Comiple time check that loggingErrorHandler implements ErrorHandler.
_ otel.ErrorHandler = (*loggingErrorHandler)(nil)
)
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// loggingErrorHandler logs all errors to STDERR.
type loggingErrorHandler struct {
delegate atomic.Value
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l *log.Logger
}
// setDelegate sets the ErrorHandler delegate if one is not already set.
func (h *loggingErrorHandler) setDelegate(d otel.ErrorHandler) {
if h.delegate.Load() != nil {
// Delegate already registered
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return
}
h.delegate.Store(d)
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}
// Handle implements otel.ErrorHandler.
func (h *loggingErrorHandler) Handle(err error) {
if d := h.delegate.Load(); d != nil {
d.(otel.ErrorHandler).Handle(err)
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return
}
h.l.Print(err)
}
// ErrorHandler returns the global ErrorHandler instance. If no ErrorHandler
// instance has been set (`SetErrorHandler`), the default ErrorHandler which
// logs errors to STDERR is returned.
func ErrorHandler() otel.ErrorHandler {
return globalErrorHandler
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}
// SetErrorHandler sets the global ErrorHandler to be h.
func SetErrorHandler(h otel.ErrorHandler) {
delegateErrorHandlerOnce.Do(func() {
current := ErrorHandler()
if current == h {
return
}
if internalHandler, ok := current.(*loggingErrorHandler); ok {
internalHandler.setDelegate(h)
}
})
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}
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// Handle is a convience function for ErrorHandler().Handle(err)
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func Handle(err error) {
ErrorHandler().Handle(err)
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}