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Clone the collectd repo: https://github.com/collectd/collectd.git

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

...

Code Block
#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__);
  /*  In order to dispatch values to the collectd daemon you need to fill out a value list and use plugin_dispatch_values() An example is provided below
   *
   *  value_list_t vl = VALUE_LIST_INIT;
   *
   *  vl.values = &(value_t){.derive = value}; //NOTE please change value to the actual value and use an appropriate type: checkout https://wiki.opnfv.org/display/fastpath/Collectd+101 for more info
   *
   *  vl.values_len = 1;
   *  sstrncpy(vl.host, hostname_g, sizeof(vl.host));
   *  sstrncpy(vl.plugin, PLUGIN_NAME, sizeof(vl.plugin));
   *  sstrncpy(vl.plugin_instance, "my_plugin_instance", sizeof(vl.plugin_instance)); // replace my_plugin_instance with an appropriate string/instance... see the end of this wiki
   *  sstrncpy(vl.type, "my_plugin_type", sizeof(vl.type));// replace my_plugin_type with an appropriate string... see the end of this wiki
   *
   *  plugin_dispatch_values(&vl);
   *
   *
   * To dispatch a notification you need to fill out a notification structure and use plugin_dispatch_notification()
   *  notification_t n = {
   *      .severity = severity, // where severity is one of NOTIF_OKAY, NOTIF_WARNING, NOTIF_FAILURE
   *      .time = cdtime(), 
   *      .message = "Some message",
   *      .plugin = PLUGIN_NAME}; 
   *
   *  sstrncpy(n.host, hostname_g, sizeof(n.host));
   *  sstrncpy(n.plugin_instance, "my_plugin_instance", sizeof(n.plugin_instance)); // replace my_plugin_instance with an appropriate string... see the end of this wiki
   *
   *  plugin_dispatch_notification(&n);
   */


  return (0);
}
 
 
static int my_shutdown_function (void) {
 
  INFO (PLUGIN_NAME ": %s:%d", __FUNCTION__, __LINE__);
 
  return (0);
}
 
static int 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);
}
 

 

Under src/ Modify the types.db file to include a new type

Code Block
my_plugin_type            value:DERIVE:0:U

 

Under the top level collectd directory Modify the Makefile.am file to build your plugin

Code Block
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

 

 

Under the top level collectd directory 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):

...

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

 

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

Code Block
#@BUILD_PLUGIN_MY_PLUGIN_TRUE@LoadPlugin my_plugin


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

 

 

Under src/ Update the plugin configuration description in collectd.conf.pod

Code Block
=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>B<Option2> I<some_string>


TBD.


=back

...

you should now be able to build your simple collectd plugin, in the top level directory:

Code Block
$ ./build.sh
$ ./configure --prefix=$HOME/clct
--enable-debug
$ make
$ make -j install

 

...

Code Block
$ cd $HOME/clct

 

Edit etc/collectd.conf to include:

Code Block
LoadPlugin my_plugin
LoadPlugin logfile

<Plugin logfile>
        LogLevel debug
        File STDOUT
        Timestamp true
        PrintSeverity false
</Plugin>

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

 

Run collectd:

Code Block
sbin/collectd -f -C etc/collectd.conf

 

Extra Challenge:

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

...

Value listExamplecomment
Values 99.8999111112112percentage 
Value lengththe number of values in the data set.  
Timetimestamp at which the value was collected.1475837857epoch
Intervalinterval at which to expect a new value.10interval
Hostused to identify the host.localhostcan be uuid for vm or host… or can give host a name
Pluginused to identify the plugin.cpunetwork 
Plugin instance (optional)used to group a set of values together. For e.g. values belonging to a DPDK interface.0eth0 
Typeunit used to measure a value. In other words used to refer to a data set.percentpackets 
Type instance (optional)used to distinguish between values that have an identical type.userrx or tx 
meta dataan opaque data structure that enables the passing of additional information about a value list. “Meta data in the global cache can be used to store arbitrary information about an identifier”   

...