Updating level a logger without creating a new pointer

[adibrastegarnia]

Currently, I was trying to update the level of a logger by creating a new one an assign it to the old one but I noticed these two are pointing to different addresses and won't be useful during runtime. Like this:

newLogger := loggerNode.stdLogger.WithOptions(
				zp.WrapCore(
					func(zc.Core) zc.Core {
						return zc.NewCore(loggerNode.encoder, loggerNode.writer, &newLevel)
					}))

I am wondering is it possible to change the level of a logger without recreating a new logger? Please consider that I wrote a custom logger.

[prashantv]

You can update the level of a logger by:

1. Creating an AtomicLevel, hold on to the reference to the AtomicLevel
2. Create logger by passing in the above AtomicLevel as the level to the logger
3. Update the level by using using SetLevel on the AtomicLevel:
   https://godoc.org/go.uber.org/zap#AtomicLevel.SetLevel

[adibrastegarnia]

@prashantv
Thanks. Let me try it.

[adibrastegarnia]

@prashantv
That works fine. Thanks. I have the same question for the writerSyncer. At runtime, I want to change it to a sink without recreating the logger. I did almost the same thing by updating the the value of pointer to the writer but it doesn't work. Any suggestions?

[prashantv]

We don't have official support for a write syncer that can be changed, but since it's an interface you can build your own implementation that does allow changing the underlying WriteSyncer, something like:

type AtomicWriteSyncer struct{
  underlying atomic.Value // WriteSyncer
}

func NewAtomicWriteSyncer(ws zapcore.WriteSyncer) zapcore.WriteSyncer {
  return &AtomicWriteSyncer{ws}
}

func (w *AtomicWriteSyncer) writeSyncer() zapcore.WriteSyncer {
  return underlying.Load().(zapcore.WriteSyncer)
}

func (w *AtomicWriteSyncer) SetWriteSyncer(new zapcore.WriteSyncer) {
  w.underlying.Store(new)
}

func (w *AtomicWriteSyncer) Write(p []byte) (int, error) {
  return w.writeSyncer().Write(p)
}

func (w *AtomicWriteSyncer) Sync() error {
  return w.writeSyncer().Sync()
}

You would hold the reference to the above AtomicWriteSyncer so you can change it dynamically.

[adibrastegarnia]

@prashantv
Thanks for your response. I will try it out.