NAME

       collectd-lua - Documentation of collectd's "Lua plugin"

SYNOPSIS

         LoadPlugin lua
         # ...
         <Plugin lua>
           BasePath "/path/to/your/lua/scripts"
           Script "script1.lua"
           Script "script2.lua"
         </Plugin>

DESCRIPTION

       The "Lua plugin" embeds a Lua interpreter into collectd and provides an interface to
       collectd's plugin system. This makes it possible to write plugins for collectd in Lua.
       This is a lot more efficient than executing a Lua script every time you want to read a
       value with the "exec plugin" (see collectd-exec(5)) and provides a lot more functionality,
       too.

       The minimum required Lua version is 5.1.

CONFIGURATION

       LoadPlugin Lua
           Loads the Lua plugin.

       BasePath Name
           The directory the "Lua plugin" looks in to find script Script.  If set, this is also
           prepended to package.path.

       Script Name
           The script the "Lua plugin" is going to run.  If BasePath is not specified, this needs
           to be an absolute path.

WRITING YOUR OWN PLUGINS

       Writing your own plugins is quite simple. collectd manages plugins by means of dispatch
       functions which call the appropriate callback functions registered by the plugins. Any
       plugin basically consists of the implementation of these callback functions and
       initializing code which registers the functions with collectd. See the section "EXAMPLES"
       below for a really basic example. The following types of callback functions are
       implemented in the Lua plugin (all of them are optional):

       read functions
           These are used to collect the actual data. It is called once per interval (see the
           Interval configuration option of collectd). Usually it will call
           collectd.dispatch_values to dispatch the values to collectd which will pass them on to
           all registered write functions. If this function does not return 0, interval between
           its calls will grow until function returns 0 again. See the MaxReadInterval
           configuration option of collectd.

       write functions
           These are used to write the dispatched values. They are called once for every value
           that was dispatched by any plugin.

FUNCTIONS

       The following functions are provided to Lua modules:

       register_read(callback)
           Function to register read callbacks.  The callback will be called without arguments.
           If this callback function does not return 0 the next call will be delayed by an
           increasing interval.

       register_write(callback)
           Function to register write callbacks.  The callback function will be called with one
           argument passed, which will be a table of values.  If this callback function does not
           return 0 next call will be delayed by an increasing interval.

       log_error, log_warning, log_notice, log_info, log_debug(message)
           Log a message with the specified severity.

EXAMPLES

           A very simple read function might look like:

             function read()
               collectd.log_info("read function called")
               t = {
                   host = 'localhost',
                   plugin = 'myplugin',
                   type = 'counter',
                   values = {42},
               }
               collectd.dispatch_values(t)
               return 0
             end

           A very simple write function might look like:

             function write(vl)
               for i = 1, #vl.values do
                 collectd.log_info(vl.host .. '.' .. vl.plugin .. '.' .. vl.type .. ' ' .. vl.values[i])
               end
               return 0
             end

           To register those functions with collectd:

             collectd.register_read(read)     -- pass function as variable
             collectd.register_write("write") -- pass by global-scope function name

SEE ALSO

       collectd(1), collectd.conf(5), lua(1),

AUTHOR

       The "Lua plugin" has been written by Julien Ammous <j.ammous at gmail.com>, Florian
       Forster <octo at collectd.org> and Ruben Kerkhof <ruben at rubenkerkhof.com>.

       This manpage has been written by Ruben Kerkhof <ruben at rubenkerkhof.com>.  It is based
       on the collectd-perl(5) manual page by Florian Forster <octo at collectd.org> and
       Sebastian Harl <sh at tokkee.org>.