modern syslog - streaming, async, native, uses nan

This is the only syslog library that:

Uses native bindings to the libc syslog API.
Is async, because the libc APIs can block on localhost IPC under load, but that shouldn't block your app.
Can be used as a stream.
Has formatted log functions.
Uses nan, so supports node and io.js, and will continue to do so.
Is API compatible with node-syslog, from which I gathered inspiration and owe thanks.

Default mask depends on system.

Installation

npm install --save modern-syslog

API

For detailed descriptions of the core functions, see man 3 syslog.

Note that syslog functions cannot fail, and neither throw errors, nor callback with errors. This is consistent with the core functions, which do not have error return values.

log(priority, msg, callback)

priority {String|Number} OR of a level, and optionally, a facility.
msg {String|Buffer} Message to log.
callback {Function} Called after message is logged (no arguments).

priority can be a String, in which case it will be looked up in syslog.level. It can also be a Number, in which case it is expected to be a numeric value, such as syslog.level.LOG_INFO, optionally ORed with a a numeric facility, such as syslog.facility.LOG_LOCAL2.

See below for formatted version of log().

emerg(fmt, ...)

alert(fmt, ...)

crit(fmt, ...)

error(fmt, ...)

err(fmt, ...)

warn(fmt, ...)

warning(fmt, ...)

note(fmt, ...)

notice(fmt, ...)

info(fmt, ...)

debug(fmt, ...)

fmt {String} Arguments are formatted as msg, and passed to log().

Convenience functions, log level is pre-defined, facility uses default, either system default or that provided to open(), and message is formatted with util.format().

new Stream(level, [facility])

level {String|Number} Level to log at.
facility {String|Number} Facility to log with, optional.

Returns a writeable stream that logs all messages at the specified level and facility.

open(ident, option, facility)

ident {String} Prepended to every message, usually program name.
option {Number} OR of flags from syslog.options.
facility {String|Number} Default facility to be used by log().

Set up defaults for log.

Calling open() is optional, all arguments are provided with defaults, though the defaults depend on the system (see man page).

close()

Close the socket to the syslog system.

Calling close() is optional, the socket is closed automatically by the system on exit.

upto(level)

level {String|Number} Level to log up to.

Log all levels upto and including level.

setmask(mask)

mask {Number} OR of levels that should be logged.

Not convenient to use but part of the low-level syslog API. See syslog man page for details, and consider using upto() for most common use-cases.

curmask()

Returns current log mask, see setmask().

setMask(...)

Avoid this, its for backwards compatibility with node-syslog.

init(...)