108 lines
3.3 KiB
Go
108 lines
3.3 KiB
Go
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// Copyright The OpenTelemetry Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package otel // import "go.opentelemetry.io/otel"
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import (
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"log"
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"os"
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"sync"
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"sync/atomic"
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)
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var (
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// globalErrorHandler provides an ErrorHandler that can be used
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// throughout an OpenTelemetry instrumented project. When a user
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// specified ErrorHandler is registered (`SetErrorHandler`) all calls to
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// `Handle` and will be delegated to the registered ErrorHandler.
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globalErrorHandler = defaultErrorHandler()
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// delegateErrorHandlerOnce ensures that a user provided ErrorHandler is
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// only ever registered once.
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delegateErrorHandlerOnce sync.Once
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// Compile-time check that delegator implements ErrorHandler.
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_ ErrorHandler = (*delegator)(nil)
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)
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type holder struct {
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eh ErrorHandler
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}
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func defaultErrorHandler() *atomic.Value {
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v := &atomic.Value{}
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v.Store(holder{eh: &delegator{l: log.New(os.Stderr, "", log.LstdFlags)}})
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return v
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}
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// delegator logs errors if no delegate is set, otherwise they are delegated.
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type delegator struct {
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delegate atomic.Value
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l *log.Logger
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}
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// setDelegate sets the ErrorHandler delegate.
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func (h *delegator) setDelegate(d ErrorHandler) {
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// It is critical this is guarded with delegateErrorHandlerOnce, if it is
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// called again with a different concrete type it will panic.
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h.delegate.Store(d)
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}
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// Handle logs err if no delegate is set, otherwise it is delegated.
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func (h *delegator) Handle(err error) {
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if d := h.delegate.Load(); d != nil {
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d.(ErrorHandler).Handle(err)
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return
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}
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h.l.Print(err)
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}
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// GetErrorHandler returns the global ErrorHandler instance.
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//
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// The default ErrorHandler instance returned will log all errors to STDERR
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// until an override ErrorHandler is set with SetErrorHandler. All
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// ErrorHandler returned prior to this will automatically forward errors to
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// the set instance instead of logging.
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//
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// Subsequent calls to SetErrorHandler after the first will not forward errors
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// to the new ErrorHandler for prior returned instances.
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func GetErrorHandler() ErrorHandler {
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return globalErrorHandler.Load().(holder).eh
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}
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// SetErrorHandler sets the global ErrorHandler to h.
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//
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// The first time this is called all ErrorHandler previously returned from
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// GetErrorHandler will send errors to h instead of the default logging
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// ErrorHandler. Subsequent calls will set the global ErrorHandler, but not
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// delegate errors to h.
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func SetErrorHandler(h ErrorHandler) {
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delegateErrorHandlerOnce.Do(func() {
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current := GetErrorHandler()
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if current == h {
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return
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}
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if internalHandler, ok := current.(*delegator); ok {
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internalHandler.setDelegate(h)
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}
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})
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globalErrorHandler.Store(holder{eh: h})
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}
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// Handle is a convenience function for ErrorHandler().Handle(err)
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func Handle(err error) {
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GetErrorHandler().Handle(err)
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}
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