Introduce telemetry framework

Adds base/frameworks/telemetry with wrappers around telemetry.bif
and updates telemetry/Manager to support collecting metrics from
script land.

Add policy/frameworks/telemetry/log for logging of metrics data
into a new telemetry.log and telemetry_histogram.log and add into
local.zeek by default.

src/telemetry/Manager.h

@@ -5,6 +5,8 @@
 #include <cstdint>
 #include <initializer_list>
 #include <string_view>
+#include <unordered_map>
+#include <variant>
 #include <vector>
 
 #include "zeek/IntrusivePtr.h"
@@ -20,6 +22,12 @@ namespace broker
 class endpoint;
 	}
 
+namespace zeek
+	{
+class RecordVal;
+using RecordValPtr = IntrusivePtr<RecordVal>;
+	}
+
 namespace zeek::Broker
 	{
 class Manager;
@@ -50,6 +58,128 @@ public:
 	 */
 	virtual void InitPostScript();
 
+	/**
+	 * Supported metric types.
+	 */
+	enum class MetricType
+		{
+		Counter,
+		Gauge,
+		Histogram
+		};
+
+	/**
+	 * Captures information about counter and gauge metrics.
+	 */
+	struct CollectedValueMetric
+		{
+		/**
+		 * Constructor.
+		 * @param metric_type The type of this metric.
+		 * @param family Broker layer family handle for this metric.
+		 * @param label_values The string values for each of the metric's labels.
+		 * @param value The metric's current value.
+		 */
+		CollectedValueMetric(MetricType metric_type,
+		                     const broker::telemetry::metric_family_hdl* family,
+		                     std::vector<std::string_view> label_values,
+		                     std::variant<double, int64_t> value)
+			: metric_type(metric_type), family(family), label_values(std::move(label_values)),
+			  value(value)
+			{
+			}
+
+		/**
+		 * @return A script layer Telemetry::Metric record for this metric.
+		 */
+		zeek::RecordValPtr AsMetricRecord() const;
+
+		enum MetricType metric_type;
+		const broker::telemetry::metric_family_hdl* family;
+		std::vector<std::string_view> label_values;
+		std::variant<double, int64_t> value;
+		};
+
+	/**
+	 * Captures information about histogram metrics.
+	 */
+	struct CollectedHistogramMetric
+		{
+		/**
+		 * Helper struct representing a single bucket of a histogram.
+		 * @tparam T The data type used by the histogram (double or int64_t).
+		 */
+		template <class T> struct Bucket
+			{
+			Bucket(T count, T upper_bound) : count(count), upper_bound(upper_bound) { }
+
+			T count;
+			T upper_bound;
+			};
+
+		/**
+		 * Helper struct representing a histogram as sum and buckets.
+		 * @tparam T The data type used by the histogram (double or int64_t).
+		 */
+		template <class T> struct HistogramData
+			{
+			T sum;
+			std::vector<Bucket<T>> buckets;
+			};
+
+		using DblHistogramData = HistogramData<double>;
+		using IntHistogramData = HistogramData<int64_t>;
+
+		/**
+		 * Constructor.
+		 * @param family Broker layer family handle for this metric.
+		 * @param label_values The string values for each of the metric's labels.
+		 * @param histogram The histogram's data (sum and individual buckets).
+		 */
+		CollectedHistogramMetric(const broker::telemetry::metric_family_hdl* family,
+		                         std::vector<std::string_view> label_values,
+		                         std::variant<DblHistogramData, IntHistogramData> histogram)
+
+			: family(family), label_values(std::move(label_values)), histogram(std::move(histogram))
+			{
+			}
+
+		const broker::telemetry::metric_family_hdl* family;
+		std::vector<std::string_view> label_values;
+		std::variant<DblHistogramData, IntHistogramData> histogram;
+
+		/**
+		 * @return A script layer Telemetry::HistogramMetric record for this histogram.
+		 */
+		zeek::RecordValPtr AsHistogramMetricRecord() const;
+		};
+
+	/**
+	 * @return A script layer Telemetry::MetricOpts record for the given metric family.
+	 * @param metric_typ The type of metric.
+	 * @param family Broker layer family handle for the family.
+	 * @tparam T The underlying data type (double or int64_t)
+	 */
+	template <typename T>
+	zeek::RecordValPtr GetMetricOptsRecord(MetricType metric_type,
+	                                       const broker::telemetry::metric_family_hdl* family);
+
+	/**
+	 * @return All counter and gauge metrics and their values matching prefix and name.
+	 * @param prefix The prefix pattern to use for filtering. Supports globbing.
+	 * @param name The name pattern to use for filtering. Supports globbing.
+	 */
+	std::vector<CollectedValueMetric> CollectMetrics(std::string_view prefix,
+	                                                 std::string_view name);
+
+	/**
+	 * @return All histogram metrics and their data matching prefix and name.
+	 * @param prefix The prefix pattern to use for filtering. Supports globbing.
+	 * @param name The name pattern to use for filtering. Supports globbing.
+	 */
+	std::vector<CollectedHistogramMetric> CollectHistogramMetrics(std::string_view prefix,
+	                                                              std::string_view name);
+
 	/**
 	 * @return A counter metric family. Creates the family lazily if necessary.
 	 * @param prefix The prefix (namespace) this family belongs to.
@@ -414,6 +544,11 @@ protected:
 	void InitPostBrokerSetup(broker::endpoint&);
 
 	IntrusivePtr<broker::telemetry::metric_registry_impl> pimpl;
+
+private:
+	// Caching of metric_family_hdl instances to their Zeek record representation.
+	std::unordered_map<const broker::telemetry::metric_family_hdl*, zeek::RecordValPtr>
+		metric_opts_cache;
 	};
 
 	} // namespace zeek::telemetry