add Prometheus library

Prometheus/samples/MetricsSample/src/MetricsSample.cpp

@@ -0,0 +1,95 @@
+#include "Poco/Prometheus/Counter.h"
+#include "Poco/Prometheus/Gauge.h"
+#include "Poco/Prometheus/Histogram.h"
+#include "Poco/Prometheus/CallbackMetric.h"
+#include "Poco/Prometheus/ProcessCollector.h"
+#include "Poco/Prometheus/ThreadPoolCollector.h"
+#include "Poco/Prometheus/MetricsServer.h"
+#include "Poco/Util/ServerApplication.h"
+#include <iostream>
+#include <cmath>
+
+
+using Poco::Util::ServerApplication;
+using namespace std::string_literals;
+using namespace Poco::Prometheus;
+
+
+class MetricsSampleApp: public ServerApplication
+{
+protected:
+	void initialize(Application& self)
+	{
+		loadConfiguration(); // load default configuration files, if present
+		ServerApplication::initialize(self);
+	}
+
+	int main(const ArgVec& args)
+	{
+		try
+		{
+			Counter counter1("test_counter"s);
+			counter1.help("A test counter"s);
+
+			counter1.inc();
+
+			Counter counter2("http_requests"s, {
+				/*.help = */"HTTP requests, grouped by method"s,
+				/*.labelNames =*/ {"method"s}
+			});
+
+			counter2.labels({"POST"s}).inc();
+			counter2.labels({"GET"s}).inc();
+
+			Counter counter3("http_requests_uri"s, {
+				/*.help =*/ "HTTP requests, grouped by method and uri"s,
+				/*.labelNames =*/ {"method"s, "path"s}
+			});
+
+			counter3.labels({"POST"s, "/metrics"}).inc(3);
+			counter3.labels({"GET"s, "/test"s}).inc();
+
+			CallbackIntCounter counter4("callback_int"s, []()
+				{
+					return 42;
+				}
+			);
+
+			Gauge gauge1("sample_count"s);
+			gauge1.help("A sample gauge"s);
+			gauge1.set(-INFINITY);
+
+			Histogram histo("sample_histogram"s, {
+				/*.help =*/ "A histogram"s,
+				/*.labelNames =*/ {},
+				/*.buckets =*/ {1.0, 2.0, 3.0}
+			});
+
+			histo.observe(0.5);
+			histo.observe(1.1);
+			histo.observe(5.0);
+			histo.observe(2.1);
+
+			ProcessCollector pc;
+			ThreadPoolCollector tpc;
+
+			const Poco::UInt16 metricsPort = static_cast<Poco::UInt16>(config().getInt("metrics.port"s, 9100));
+			MetricsServer server(metricsPort);
+			server.start();
+
+			waitForTerminationRequest();
+
+			server.stop();
+		}
+		catch (Poco::Exception& exc)
+		{
+			std::cerr << exc.displayText() << std::endl;
+			return Application::EXIT_SOFTWARE;
+		}
+
+		return Application::EXIT_OK;
+	}
+};
+
+
+POCO_SERVER_MAIN(MetricsSampleApp)