Log elements flowing through the stream as well as completion and erroring.
def log(name: String, extract: Out ⇒ Any = ConstantFun.scalaIdentityFunction)(implicit log: LoggingAdapter = null): Repr[Out]
Log elements flowing through the stream as well as completion and erroring. By default element and completion signals are logged on debug level, and errors are logged on Error level. This can be changed by calling
Attributes.createLogLevels(...) on the given Flow.
emits when upstream emits
backpressures when downstream backpressures
completes when upstream completes