Accept alternative syslog level names

[dbmikus]

Syslog has the following log level names:

• "emerg" (also "panic")
• "alert"
• "crit"
• "err" (also "error")
• "warning" (also "warn")
• "notice"
• "info"
• "debug"

Currently, this transport will not recognize using the names "warn", "err", and "panic". I know it is trying to just have parity with the log levels defined in the winston.config.syslog.levels object, but I already think that is kind of messed up because that object picks and chooses which log level names to use. For example, it uses "error" instead of "err" but uses the default level names for the rest of the levels.

I think it would be nice for the syslog transport module to allow all of the names above. Of course, the decision is up to the repository maintainers. It doesn't look like we actually use the numerical values corresponding to log level keywords, so the extra keywords could probably just be added in.

Like:

var levels = Object.keys({
  debug: 0,
  info: 1,
  notice: 2,
  warning: 3,
  warn: 3,
  err: 4,
  error: 4,
  crit: 5,
  alert: 6,
  emerg: 7,
  panic: 7
});

[dbmikus]

Or stuff could be changed to rely on the log level numerical value. This conflicts with an issue with winston.config.syslog.levels where the levels are reversed in Winston, which is actually the opposite of the levels in syslog. That is, "emerg" is considered 0 by syslog but should be 7 in winston.config.syslog.levels, however winston.config.syslog.levels currently has it as 0. See: winstonjs/winston#307

I'm not sure if using the number would mess with the message sent to syslog over the socket, though.

[ktarplee]

To have correct log level control from winston I had to reverse the numbers so that debug is 0 such as

//winston.setLevels(winston.config.syslog.levels); //this has the wrong sense
winston.setLevels({
emerg: 7,
alert: 6,
crit: 5,
error: 4,
warning: 3,
notice: 2,
info: 1,
debug: 0
});

[markstos]

winston-rsyslog2 has support for mapping winston level names to syslog levels. You are welcome to port the code over. It's possible winston-rsyslog2 may work directly with syslog, but this hasn't been tested.