Collectd simple plugin

An Overview of the architecture of a collectd plugin exists here: https://collectd.org/wiki/index.php/Plugin_architecture

To start off creating a plugin, create a c file under the src directory in collectd, the c file should have:

A config function
An init function
A read function
A shutdown function
A function to register callbacks for all the functions above.

#include "collectd.h"
#include "common.h"
 
#define PLUGIN_NAME "my_plugin"
 
static _Bool g_enable_option1;
static char g_option2 [DATA_MAX_NAME_LEN];
 
static int my_config_function(oconfig_item_t *ci) {
  int ret = 0;
 
  INFO (PLUGIN_NAME ": %s:%d", __FUNCTION__, __LINE__);
 
  for (int i = 0; i < ci->children_num; i++) {
    oconfig_item_t *child = ci->children + i;
 
    if (strcasecmp("Option1", child->key) == 0) {
      ret = cf_util_get_boolean(child, & g_enable_option1);
    } else if (strcasecmp("Option2 ", child->key) == 0) {
      ret = cf_util_get_string_buffer(child, g_option2,
                                sizeof(g_option2));
 
    }else {
      ERROR(PLUGIN_NAME ": Unknown configuration parameter \"%s\".", child->key);
      ret = (-1);
    }
 
    if (ret != 0) {
      INFO (PLUGIN_NAME ": %s:%d ret=%d", __FUNCTION__, __LINE__, ret);
      return ret;
    }
  }
 
  return (0);
}
 
 
static int my_read_function(__attribute__((unused)) user_data_t *ud) {
 
  INFO (PLUGIN_NAME ": %s:%d", __FUNCTION__, __LINE__);
 
  return (0);
}
 
 
static int my_shutdown_function (void) {
 
  INFO (PLUGIN_NAME ": %s:%d", __FUNCTION__, __LINE__);
 
  return (0);
}
 
static my_init_function(void) {
  INFO(PLUGIN_NAME ": %s:%d", __FUNCTION__, __LINE__);
 
  return (0);
}
 
 
void module_register(void) {
 plugin_register_init("my_plugin", my_init_function);
  plugin_register_complex_config("my_plugin", my_config_function);
  plugin_register_complex_read(NULL, "my_plugin", my_read_function, 0, NULL);
  plugin_register_shutdown("my_plugin", my_shutdown_function);
}

Modify the Makefile.am file to build your plugin

if BUILD_PLUGIN_MY_PLUGIN
pkglib_LTLIBRARIES += my_plugin.la
my_plugin_la_SOURCES = src/my_plugin.c
my_plugin_la_CFLAGS = $(AM_CFLAGS)
my_plugin_la_LDFLAGS = $(PLUGIN_LDFLAGS)
endif

Modify the configure.ac file to include your plugin (search for plugin_ascent="no" and add it in the correct place alphpbetically), and set it to disabled (so it doesn’t build on all platforms):

plugin_my_plugin="no"

configure (in configure.ac) your plugin so that it’s enabled on linux under:

# Linux
if test "x$ac_system" = "xLinux"; then
 
plugin_my_plugin="yes"

Configure (in configure.ac) your plugin to report if it’s enabled or not:

AC_PLUGIN([my_plugin],           [$plugin_my_plugin],     [plugin desc])

In configure.ac under: “AC_MSG_RESULT([ Modules:])”, enable reporting on the plugin status from the configuration step:

AC_MSG_RESULT([    my_plugin. . . . . . $enable_my_plugin])

Finally it’s time to configure the configuration stanzas for your new plugin. By modifygin collectd.conf.in to include:

#@BUILD_PLUGIN_MY_PLUGIN _TRUE@LoadPlugin my_plugin


#<Plugin my_plugin>
#    Option1 true
#    Option2 “example”
#</Plugin>

Update the plugin configuration description in collectd.conf.pod

=head2 Plugin C<my_plugin>


The I< my_plugin > plugin collects TBD.


B<Synopsis:>


  <Plugin my_plugin>
    Option1 true
    Option2 “example”
  </Plugin>


B<Options:>


=over 2


=item B<Option1> B<false>|B<true>


TBD.


=item B< Option2> I<some_string>


TBD.


=back

you should now be able to build your simple collectd plugin:

$ ./build.sh
$ ./configure --prefix=$HOME/clct
$ make
$ make -j install

Extra bit of homework:

Try to add a double plugin configuration option and read it in with: cf_util_get_double
Write the configuration parameters to the collectd logfile