The logging level for httpuv can be set to report differing levels of
information. Possible logging levels (from least to most information
reported) are: "OFF", "ERROR", "WARN", "INFO", or
"DEBUG". The default level is ERROR.
logLevel(level = NULL)The logging level. Must be one of NULL, "OFF",
"ERROR", "WARN", "INFO", or "DEBUG". If
NULL (the default), then this function simply returns the current
logging level.
If level=NULL, then this returns the current logging level. If
level is any other value, then this returns the previous logging
level, from before it is set to the new value.