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#include <prometheus/registry.h>
#include <prometheus/counter.h>
#include <prometheus/text_serializer.h>
#include <array>
#include <chrono>
#include <cstdlib>
#include <memory>
#include <string>
#include <thread>
#include <iostream>
int main() {
using namespace prometheus;
// for clarity, we deduce the required types
using IntegerCounter = Counter<uint64_t>;
using FloatingCounter = Counter<double>;
using IntegerCounterFamily = CustomFamily<IntegerCounter>;
using FloatingCounterFamily = CustomFamily<FloatingCounter>;
// create a metrics registry
// @note it's the users responsibility to keep the object alive
Registry 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/
FloatingCounterFamily& packet_counter{ FloatingCounter::Family::Build(registry, "observed_packets_total", "Number of observed packets") };
// add and remember dimensional data, incrementing those is very cheap
FloatingCounter& tcp_rx_counter{ packet_counter.Add({ {"protocol", "tcp"}, {"direction", "rx"} }) };
FloatingCounter& tcp_tx_counter{ packet_counter.Add({ {"protocol", "tcp"}, {"direction", "tx"} }) };
FloatingCounter& udp_rx_counter{ packet_counter.Add({ {"protocol", "udp"}, {"direction", "rx"} }) };
FloatingCounter& 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
IntegerCounterFamily& http_requests_counter = IntegerCounter::Family::Build(registry, "http_requests_total", "Number of HTTP requests");
for (;; ) {
std::this_thread::sleep_for(std::chrono::seconds(1));
const int random_value = std::rand();
if (random_value & 1) tcp_rx_counter++;
if (random_value & 2) ++tcp_tx_counter;
if (random_value & 4) udp_rx_counter += 0.5;
if (random_value & 8) udp_tx_counter += 0.7;
const std::array<std::string, 4> methods = { "GET", "PUT", "POST", "HEAD" };
const std::string& method = methods.at(static_cast<std::size_t>(random_value) % methods.size());
// dynamically calling Family<T>.Add() works but is slow and should be avoided
http_requests_counter.Add({ {"method", method} }) += 10;
TextSerializer text_serializer;
text_serializer.Serialize(std::cout, registry.Collect());
}
}
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