feat(webserver): implement metrics endpoint

This endpoint currently returns only prometheus metrics.

Signed-off-by: Samuel Gaist <samuel.gaist@idiap.ch>

falco.yaml

@@ -1003,6 +1003,7 @@ metrics:
   libbpf_stats_enabled: true
   convert_memory_to_mb: true
   include_empty_values: false
+  prometheus_enabled: false
 
 #######################################
 # Falco performance tuning (advanced) #

userspace/falco/app/actions/start_webserver.cpp

@@ -44,8 +44,18 @@ falco::app::run_result falco::app::actions::start_webserver(falco::app::state& s
 			+ std::to_string(s.config->m_webserver_listen_port)
 			+ ssl_option + "\n");
 
+		std::vector<libs::metrics::libs_metrics_collector> metrics_collectors;
+		if (s.config->m_metrics_prometheus_enabled && s.config->m_metrics_prometheus_enabled)
+		{
+			for (const auto& source_info: s.source_infos)
+			{
+				metrics_collectors.push_back(libs::metrics::libs_metrics_collector(source_info.inspector.get(), s.config->m_metrics_flags));
+			}
+		}
+
 		s.webserver.start(
 			s.offline_inspector,
+			metrics_collectors,
 			s.config->m_webserver_threadiness,
 			s.config->m_webserver_listen_port, 
 			s.config->m_webserver_listen_address,

userspace/falco/configuration.cpp

@@ -79,7 +79,8 @@ falco_configuration::falco_configuration():
 	m_metrics_output_file(""),
 	m_metrics_flags((METRICS_V2_KERNEL_COUNTERS | METRICS_V2_LIBBPF_STATS | METRICS_V2_RESOURCE_UTILIZATION | METRICS_V2_STATE_COUNTERS)),
 	m_metrics_convert_memory_to_mb(true),
-	m_metrics_include_empty_values(false)
+	m_metrics_include_empty_values(false),
+	m_metrics_prometheus_enabled(false)
 {
 }
 
@@ -553,6 +554,7 @@ void falco_configuration::load_yaml(const std::string& config_name)
 
 	m_metrics_convert_memory_to_mb = config.get_scalar<bool>("metrics.convert_memory_to_mb", true);
 	m_metrics_include_empty_values = config.get_scalar<bool>("metrics.include_empty_values", false);
+	m_metrics_prometheus_enabled = config.get_scalar<bool>("metrics.prometheus_enabled", false);
 
 	std::vector<std::string> load_plugins;
 

userspace/falco/configuration.h

@@ -158,6 +158,7 @@ public:
 	uint32_t m_metrics_flags;
 	bool m_metrics_convert_memory_to_mb;
 	bool m_metrics_include_empty_values;
+	bool m_metrics_prometheus_enabled;
 	std::vector<plugin_config> m_plugins;
 
 	// Falco engine

userspace/falco/webserver.cpp

@@ -27,6 +27,7 @@ falco_webserver::~falco_webserver()
 
 void falco_webserver::start(
         const std::shared_ptr<sinsp>& inspector,
+        const std::vector<libs::metrics::libs_metrics_collector>& metrics_collectors,
         uint32_t threadiness,
         uint32_t listen_port,
         std::string& listen_address,
@@ -68,6 +69,28 @@ void falco_webserver::start(
             res.set_content(versions_json_str, "application/json");
         });
 
+    if (!metrics_collectors.empty())
+    {
+        libs::metrics::prometheus_metrics_converter prometheus_metrics_converter;
+
+        m_server->Get("/metrics",
+            [metrics_collectors, prometheus_metrics_converter](const httplib::Request &, httplib::Response &res) {
+                std::string prometheus_text;
+
+                for (auto metrics_collector: metrics_collectors) {
+                    metrics_collector.snapshot();
+                    auto metrics_snapshot = metrics_collector.get_metrics();
+
+                    for (auto& metric: metrics_snapshot)
+                    {
+                       prometheus_metrics_converter.convert_metric_to_unit_convention(metric);
+                       prometheus_text += prometheus_metrics_converter.convert_metric_to_text_prometheus(metric, "namespace", "falco") + "\n";
+                    }
+                }
+
+                res.set_content(prometheus_text, "text/plain; version=0.0.4");
+            });
+    }
     // run server in a separate thread
     if (!m_server->is_valid())
     {
@@ -118,10 +141,7 @@ void falco_webserver::stop()
         {
             m_server_thread.join();
         }
-        if (m_server != nullptr)
-        {
         m_server = nullptr;
-        }
         m_running = false;
     }
 }

userspace/falco/webserver.h

@@ -36,6 +36,7 @@ public:
 	falco_webserver& operator = (const falco_webserver&) = delete;
 	virtual void start(
 		const std::shared_ptr<sinsp>& inspector,
+		const std::vector<libs::metrics::libs_metrics_collector>& metrics_collectors,
 		uint32_t threadiness,
 		uint32_t listen_port,
 		std::string& list_address,