Defines a callback that will be invoked when the HTTP route is called. More...

#include <res_prometheus.h>

Data Fields
void(*	callback_fn )(struct ast_str **output)
	The callback function to invoke. More...

const char *	name
	The name of our callback (always useful for debugging) More...

Detailed Description

Defines a callback that will be invoked when the HTTP route is called.

This callback presents the second way of passing metrics to a Prometheus server. For metrics that are generated often or whose value needs to be stored, metrics can be created and registered. For metrics that can be obtained "on-the-fly", this mechanism is preferred. When the HTTP route is queried by promtheus, the registered callbacks are invoked. The string passed to the callback should be populated with stack-allocated metrics using prometheus_metric_to_string.

Example Usage:

static void prometheus_metric_callback(struct ast_str **output)
{
   struct prometheus_metric test_counter =
      PROMETHEUS_METRIC_STATIC_INITIALIZATION(
         PROMETHEUS_METRIC_COUNTER,
         "test_counter",
         "A test counter",
         NULL);
   prometheus_metric_to_string(&test_counter, output);
}
static void load_module(void)
{
   struct prometheus_callback callback = {
      .name = "test_callback",
      .callback_fn = &prometheus_metric_callback,
   };
   prometheus_callback_register(&callback);
}