LuaLogging: A simple API to use logging features in Lua

Remote syslog appender

This appender can be used to send syslog formatted log requests to a remote syslog server. This appender relies on LuaSocket to do its job. Optionally Copas can be used for async sending of log messages over TCP.

If you want to log to the local syslog daemon, then please use luasyslog.

The LuaLogging log-levels will be mapped to the syslog levels by their name, where logging.FATAL maps to syslog ALERT. Since LuaLogging only has 5 levels, the syslog levels EMERG, CRIT, and NOTICE remain unused.

function logging.rsyslog {
    hostname = string,
    [port = number,]
    [protocol = "udp" | "tcp",]
    [rfc = "rfc5424" | "rfc3164",]
    [maxsize = number,]
    [facility = facility-constant,]
    [ident = string,]
    [procid = string,]
    [msgid = string,]

    [logPattern = string,]
    [logPatterns = {
      [logging.DEBUG = string,]
      [logging.INFO  = string,]
      [logging.WARN  = string,]
      [logging.ERROR = string,]
      [logging.FATAL = string,]
    },]
    [logLevel = log-level-constant,]
}

hostname:
Hostname can be an IP address or a host name of the server where the log message will be sent.
port:
The port must be an integer number in the range [1..64K). The default is 514.
protocol:
The network protocol to use, either "udp" or "tcp". The default is "tcp".

Note: TCP sending is a blocking operation. For non-blocking use Copas is supported, see the example below.
rfc:
The message format. 2 options:
- for the old BSD style use "rfc3164" (the default)
- for the IETF standard use "rfc5424".
maxsize:
The maximum message size. Longer messages will be truncated. The minimum value is 480. The defaults are 1024 for "rfc3164", and 2048 for "rfc5424".

facility:
The syslog facility to use, use one of the constants. The default value is the "user" facility.

  rsyslog.FACILITY_KERN
  rsyslog.FACILITY_USER
  rsyslog.FACILITY_MAIL
  rsyslog.FACILITY_DAEMON
  rsyslog.FACILITY_AUTH
  rsyslog.FACILITY_SYSLOG
  rsyslog.FACILITY_LPR
  rsyslog.FACILITY_NEWS
  rsyslog.FACILITY_UUCP
  rsyslog.FACILITY_CRON
  rsyslog.FACILITY_AUTHPRIV
  rsyslog.FACILITY_FTP
  rsyslog.FACILITY_NTP
  rsyslog.FACILITY_SECURITY
  rsyslog.FACILITY_CONSOLE
  rsyslog.FACILITY_NETINFO
  rsyslog.FACILITY_REMOTEAUTH
  rsyslog.FACILITY_INSTALL
  rsyslog.FACILITY_RAS
  rsyslog.FACILITY_LOCAL0
  rsyslog.FACILITY_LOCAL1
  rsyslog.FACILITY_LOCAL2
  rsyslog.FACILITY_LOCAL3
  rsyslog.FACILITY_LOCAL4
  rsyslog.FACILITY_LOCAL5
  rsyslog.FACILITY_LOCAL6
  rsyslog.FACILITY_LOCAL7

ident:
The value for the APP-NAME field (rfc5424, called TAG field in rfc3164). Default value is "lua".
procid:
The process id value (only applicable for rfc5424 format). Default value is "-" (absent).
msgid:
The message id value (only applicable for rfc5424 format). Default value is "-" (absent).
logPattern:
This value will be used as the default value for each log-level that was omitted in logPatterns, this defaults to "%message". The default pattern deviates from standard LuaLogging defaults since those do not make sense for syslog.
logPatterns:
A table with logPattern strings indexed by the log-levels. A logPattern specifies how the message is written.
If this parameter is omitted, a patterns table will be created with the parameter logPattern as the default value for each log-level.
logLevel:
The initial log-level to set for the created logger.

Example

local rsyslog = require "logging.rsyslog"

rsyslog.copas() -- switch to using non-blocking Copas sockets

local logger = rsyslog {
  hostname = "syslog.mycompany.com",
  port = 514,
  protocol = "tcp",
  rfc = "rfc5424",
  maxsize = 8000,
  facility = rsyslog.FACILITY_LOCAL2,
  ident = "my_lua_app",
  procid = "socket_mod",
  logPattern = "%message %source",
}

copas.loop(function()
  logger:info("logging.rsyslog test")
  logger:debug("debugging...")
  logger:error("error!")

  -- destroy to ensure threads are shutdown (only for Copas)
  logger:destroy()
end)