Add SwapLogger.
Chris Hines
8 years ago
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// The fundamental interface is Logger. Loggers create log events from
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// key/value data.
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package log
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import "sync/atomic"
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// Logger is the fundamental interface for all log operations. Implementations
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// must be safe for concurrent use by multiple goroutines. Log creates a log
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func (f LoggerFunc) Log(keyvals ...interface{}) error {
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return f(keyvals...)
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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.
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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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// NewSwapLogger returns a pointer to a new SwapLogger that wraps logger.
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func NewSwapLogger(logger Logger) *SwapLogger {
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l := &SwapLogger{}
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l.Swap(logger)
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return l
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}
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// Log implements the Logger interface by calling Log on the currently wrapped
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// logger.
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func (l *SwapLogger) Log(keyvals ...interface{}) error {
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return l.logger.Load().(loggerStruct).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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logger.Log("k", "v")
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}
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}
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func TestSwapLogger(t *testing.T) {
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buf := &bytes.Buffer{}
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json := log.NewJSONLogger(buf)
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logger := log.NewSwapLogger(json)
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if err := logger.Log("k", "v"); err != nil {
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t.Error(err)
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}
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if got, want := buf.String(), `{"k":"v"}`+"\n"; got != want {
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t.Errorf("got %v, want %v", got, want)
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}
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buf.Reset()
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prefix := log.NewPrefixLogger(buf)
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logger.Swap(prefix)
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if err := logger.Log("k", "v"); err != nil {
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t.Error(err)
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}
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if got, want := buf.String(), "k=v\n"; got != want {
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t.Errorf("got %v, want %v", got, want)
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}
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}
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func TestSwapLoggerConcurrency(t *testing.T) {
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testConcurrency(t, log.NewSwapLogger(discard))
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}
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