feat add spdlog

src/metric_server.cc

@@ -0,0 +1,67 @@
+#include <prometheus/counter.h>
+#include <prometheus/exposer.h>
+#include <prometheus/registry.h>
+
+#include <array>
+#include <chrono>
+#include <cstdlib>
+#include <memory>
+#include <string>
+#include <thread>
+
+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;
+}