81 lines
2.3 KiB
Go
81 lines
2.3 KiB
Go
package log
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import (
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"io"
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"sync"
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"sync/atomic"
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)
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// SwapLogger wraps another logger that may be safely replaced while other
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// goroutines use the SwapLogger concurrently. The zero value for a SwapLogger
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// will discard all log events without error.
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//
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// SwapLogger serves well as a package global logger that can be changed by
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// importers.
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type SwapLogger struct {
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logger atomic.Value
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}
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type loggerStruct struct {
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Logger
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}
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// Log implements the Logger interface by forwarding keyvals to the currently
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// wrapped logger. It does not log anything if the wrapped logger is nil.
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func (l *SwapLogger) Log(keyvals ...interface{}) error {
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s, ok := l.logger.Load().(loggerStruct)
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if !ok || s.Logger == nil {
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return nil
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}
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return s.Log(keyvals...)
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}
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// Swap replaces the currently wrapped logger with logger. Swap may be called
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// concurrently with calls to Log from other goroutines.
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func (l *SwapLogger) Swap(logger Logger) {
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l.logger.Store(loggerStruct{logger})
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}
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// SyncWriter synchronizes concurrent writes to an io.Writer.
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type SyncWriter struct {
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mu sync.Mutex
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w io.Writer
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}
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// NewSyncWriter returns a new SyncWriter. The returned writer is safe for
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// concurrent use by multiple goroutines.
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func NewSyncWriter(w io.Writer) *SyncWriter {
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return &SyncWriter{w: w}
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}
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// Write writes p to the underlying io.Writer. If another write is already in
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// progress, the calling goroutine blocks until the SyncWriter is available.
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func (w *SyncWriter) Write(p []byte) (n int, err error) {
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w.mu.Lock()
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n, err = w.w.Write(p)
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w.mu.Unlock()
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return n, err
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}
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// syncLogger provides concurrent safe logging for another Logger.
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type syncLogger struct {
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mu sync.Mutex
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logger Logger
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}
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// NewSyncLogger returns a logger that synchronizes concurrent use of the
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// wrapped logger. When multiple goroutines use the SyncLogger concurrently
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// only one goroutine will be allowed to log to the wrapped logger at a time.
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// The other goroutines will block until the logger is available.
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func NewSyncLogger(logger Logger) Logger {
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return &syncLogger{logger: logger}
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}
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// Log logs keyvals to the underlying Logger. If another log is already in
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// progress, the calling goroutine blocks until the syncLogger is available.
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func (l *syncLogger) Log(keyvals ...interface{}) error {
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l.mu.Lock()
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err := l.logger.Log(keyvals...)
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l.mu.Unlock()
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return err
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}
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