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#include <array>
#include <chrono>
#include <cstdlib>
#include <memory>
#include <string>
#include <thread>
#include "prometheus/client_metric.h"
#include "prometheus/counter.h"
#include "prometheus/exposer.h"
#include "prometheus/family.h"
#include "prometheus/registry.h"
int main() {
using namespace prometheus;
// create an http server running on port 8080
Exposer exposer{"127.0.0.1:8080"};
// create a metrics registry
// @note it's the users responsibility to keep the object alive
auto registry = std::make_shared<Registry>();
// add a new counter family to the registry (families combine values with the
// same name, but distinct label dimensions)
//
// @note please follow the metric-naming best-practices:
// https://prometheus.io/docs/practices/naming/
auto& packet_counter = BuildCounter()
.Name("observed_packets_total")
.Help("Number of observed packets")
.Register(*registry);
// add and remember dimensional data, incrementing those is very cheap
auto& tcp_rx_counter =
packet_counter.Add({{"protocol", "tcp"}, {"direction", "rx"}});
auto& tcp_tx_counter =
packet_counter.Add({{"protocol", "tcp"}, {"direction", "tx"}});
auto& udp_rx_counter =
packet_counter.Add({{"protocol", "udp"}, {"direction", "rx"}});
auto& udp_tx_counter =
packet_counter.Add({{"protocol", "udp"}, {"direction", "tx"}});
// add a counter whose dimensional data is not known at compile time
// nevertheless dimensional values should only occur in low cardinality:
// https://prometheus.io/docs/practices/naming/#labels
auto& http_requests_counter = BuildCounter()
.Name("http_requests_total")
.Help("Number of HTTP requests")
.Register(*registry);
// ask the exposer to scrape the registry on incoming HTTP requests
exposer.RegisterCollectable(registry);
for (;;) {
std::this_thread::sleep_for(std::chrono::seconds(1));
const auto random_value = std::rand();
if (random_value & 1) tcp_rx_counter.Increment();
if (random_value & 2) tcp_tx_counter.Increment();
if (random_value & 4) udp_rx_counter.Increment();
if (random_value & 8) udp_tx_counter.Increment();
const std::array<std::string, 4> methods = {"GET", "PUT", "POST", "HEAD"};
auto method = methods.at(random_value % methods.size());
// dynamically calling Family<T>.Add() works but is slow and should be
// avoided
http_requests_counter.Add({{"method", method}}).Increment();
}
return 0;
}
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