new(libsinsp): add convert_metric_to_prometheus_text to metrics_colle…

…ctor

Signed-off-by: Melissa Kilby <melissa.kilby.oss@gmail.com>

userspace/libsinsp/metrics_collector.cpp

@@ -55,6 +55,22 @@ static const char *const sinsp_stats_v2_resource_utilization_names[] = {
 	[SINSP_STATS_V2_N_CONTAINERS] = "n_containers",
 };
 
+// For simplicity, needs to stay in sync w/ typedef enum metrics_v2_value_unit
+static const char *const metrics_unit_name_mappings[] = {
+	[METRIC_VALUE_UNIT_COUNT] = "COUNT",
+	[METRIC_VALUE_UNIT_PERC] = "PERC",
+	[METRIC_VALUE_UNIT_MEMORY_BYTES] = "MEMORY_BYTES",
+	[METRIC_VALUE_UNIT_MEMORY_KILOBYTES] = "MEMORY_KILOBYTES",
+	[METRIC_VALUE_UNIT_MEMORY_MEGABYTES] = "MEMORY_MEGABYTES",
+	[METRIC_VALUE_UNIT_TIME_NS] = "TIME_NS",
+};
+
+// For simplicity, needs to stay in sync w/ typedef enum metrics_v2_metric_type
+static const char *const metrics_metric_type_name_mappings[] = {
+	[METRIC_VALUE_MONOTONIC] = "MONOTONIC",
+	[METRIC_VALUE_NON_MONOTONIC_CURRENT] = "NON_MONOTONIC_CURRENT",
+};
+
 namespace libsinsp::metrics {
 
 void metrics_collector::get_rss_vsz_pss_total_memory_and_open_fds(uint32_t &rss, uint32_t &vsz, uint32_t &pss, uint64_t &memory_used_host, uint64_t &open_fds_host)
@@ -440,6 +456,43 @@ void metrics_collector::snapshot()
 	}
 }
 
+const std::string metrics_collector::convert_metric_to_prometheus_text(std::string metric_name, metrics_v2 metric) const
+{
+	std::string prometheus_text = metric_name;
+	prometheus_text += "{raw_name=\"" + std::string(metric.name) + "\",unit=\"" + std::string(metrics_unit_name_mappings[metric.unit]) \
+	+ "\",metric_type=\"" + std::string(metrics_metric_type_name_mappings[metric.metric_type]) + "\"} "; // white space at the end important!
+	switch (metric.type)
+	{
+	case METRIC_VALUE_TYPE_U32:
+		prometheus_text += std::to_string(metric.value.u32);
+		break;
+	case METRIC_VALUE_TYPE_S32:
+		prometheus_text += std::to_string(metric.value.s32);
+		break;
+	case METRIC_VALUE_TYPE_U64:
+		prometheus_text += std::to_string(metric.value.u64);
+		break;
+	case METRIC_VALUE_TYPE_S64:
+		prometheus_text += std::to_string(metric.value.s64);
+		break;
+	case METRIC_VALUE_TYPE_D:
+		prometheus_text += std::to_string(metric.value.d);
+		break;
+	case METRIC_VALUE_TYPE_F:
+		prometheus_text += std::to_string(metric.value.f);
+		break;
+	case METRIC_VALUE_TYPE_I:
+		prometheus_text += std::to_string(metric.value.i);
+		break;
+	default:
+		break;
+	}
+
+	prometheus_text += " ";
+	prometheus_text += std::to_string(sinsp_utils::get_current_time_ns());
+	return prometheus_text;
+}
+
 const std::vector<metrics_v2>& metrics_collector::get_metrics() const
 {
 	return m_metrics;

userspace/libsinsp/metrics_collector.h

@@ -87,13 +87,31 @@ class metrics_collector
 public:
 	metrics_collector(sinsp* inspector, uint32_t flags, bool convert_memory_to_mb);
 
-	// Method to fill up m_metrics_buffer with metrics; refreshes m_metrics with up-to-date metrics on each call
+	/*!
+	\brief Method to fill up m_metrics_buffer with metrics; refreshes m_metrics with up-to-date metrics on each call
+	*/
 	void snapshot();
 
-	// Method to get a const reference to m_metrics vector
+	/*!
+	\brief Method to get a const reference to m_metrics vector
+	*/
 	const std::vector<metrics_v2>& get_metrics() const;
 
-	// Method to convert memory units; tied to metrics_v2 definitions
+	/*!
+	\brief Method to convert a metric to the text-based Prometheus format.
+	 * Reference: https://github.com/prometheus/docs/blob/main/content/docs/instrumenting/exposition_formats.md
+	 * Note: The design idea is to expose Prometheus metrics by piping text-based formats to new line-delimited fields 
+	 * exposed at /metrics in Falco or a similar approach, eliminating the need for implementing a full Prometheus client.
+	 * Example:
+	 * test.memory_used_host{raw_name="memory_used_host", unit="MEMORY_MEGABYTES", metric_type="NON_MONOTONIC_CURRENT"} 15096.000000 1706490801547502000
+	 * 
+	 * This method is a work in progress.
+	*/
+	const std::string convert_metric_to_prometheus_text(std::string metric_name, metrics_v2 metric) const;
+
+	/*!
+	\brief Method to convert memory units; tied to metrics_v2 definitions
+	*/
 	template <typename T>
 	double convert_memory(metrics_v2_value_unit source_unit, metrics_v2_value_unit dest_unit, T val)
 	{

userspace/libsinsp/test/sinsp_metrics.ut.cpp

@@ -146,5 +146,19 @@ TEST_F(sinsp_with_test_input, sinsp_metrics_collector)
 	converted_memory = metrics_collector->convert_memory(METRIC_VALUE_UNIT_MEMORY_MEGABYTES, METRIC_VALUE_UNIT_MEMORY_MEGABYTES, (uint64_t)50);
 	ASSERT_EQ(converted_memory, 50);
 
+	/* Test public convert_metric_to_prometheus_text */
+	for (const auto& metric: metrics_snapshot)
+	{
+		// This resembles the Falco client use case
+		char metric_name[METRIC_NAME_MAX] = "test.";
+		strlcat(metric_name, metric.name, sizeof(metric_name));
+		std::string prometheus_text = metrics_collector->convert_metric_to_prometheus_text(metric_name, metric);
+		if (strncmp(metric.name, "n_missing_container_images", 17) == 0)
+		{
+			std::string prometheus_text_substring = "test.n_missing_container_images{raw_name=\"n_missing_container_images\",unit=\"COUNT\",metric_type=\"NON_MONOTONIC_CURRENT\"} 0";
+			ASSERT_TRUE(prometheus_text.find(prometheus_text_substring) != std::string::npos) << "Substring not found in prometheus_text";
+		}
+		ASSERT_GT(prometheus_text.length(), 8);
+	}
 }
 #endif