X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=metrics.h;h=0371668bd2a1e25c1adaed613071ac8e3c6c0551;hb=1836dccf699779d9092a75755cec96cea1734a2a;hp=519cb80f694c03756aaa34d5d809eaa1c569a722;hpb=fc65b01785b439f1ce0e8b04a33ad8abd5b4091e;p=nageru

diff --git a/metrics.h b/metrics.h
index 519cb80..0371668 100644
--- a/metrics.h
+++ b/metrics.h
@@ -7,16 +7,26 @@
 // which makes it quite unwieldy. Thus, we'll package our own for the time being.
 
 #include <atomic>
+#include <map>
+#include <memory>
 #include <mutex>
 #include <string>
-#include <map>
 #include <vector>
 
+class Histogram;
+
+// Prometheus recommends the use of timestamps instead of “time since event”,
+// so you can use this to get the number of seconds since the epoch.
+// Note that this will be wrong if your clock changes, so for non-metric use,
+// you should use std::chrono::steady_clock instead.
+double get_timestamp_for_metrics();
+
 class Metrics {
 public:
 	enum Type {
 		TYPE_COUNTER,
 		TYPE_GAUGE,
+		TYPE_HISTOGRAM,  // Internal use only.
 	};
 
 	void add(const std::string &name, std::atomic<int64_t> *location, Type type = TYPE_COUNTER)
@@ -29,30 +39,80 @@ public:
 		add(name, {}, location, type);
 	}
 
+	void add(const std::string &name, Histogram *location)
+	{
+		add(name, {}, location);
+	}
+
 	void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, std::atomic<int64_t> *location, Type type = TYPE_COUNTER);
 	void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, std::atomic<double> *location, Type type = TYPE_COUNTER);
+	void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, Histogram *location);
 
 	std::string serialize() const;
 
 private:
+	static std::string serialize_name(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels);
+	static std::string serialize_labels(const std::vector<std::pair<std::string, std::string>> &labels);
+
 	enum DataType {
 		DATA_TYPE_INT64,
 		DATA_TYPE_DOUBLE,
+		DATA_TYPE_HISTOGRAM,
 	};
+	struct MetricKey {
+		MetricKey(const std::string &name, const std::vector<std::pair<std::string, std::string>> labels)
+			: name(name), labels(labels), serialized_labels(serialize_labels(labels))
+		{
+		}
+
+		bool operator< (const MetricKey &other) const
+		{
+			if (name != other.name)
+				return name < other.name;
+			return serialized_labels < other.serialized_labels;
+		}
 
+		const std::string name;
+		const std::vector<std::pair<std::string, std::string>> labels;
+		const std::string serialized_labels;
+	};
 	struct Metric {
 		DataType data_type;
-		std::string name;
-		std::vector<std::pair<std::string, std::string>> labels;
 		union {
 			std::atomic<int64_t> *location_int64;
 			std::atomic<double> *location_double;
+			Histogram *location_histogram;
 		};
 	};
 
 	mutable std::mutex mu;
-	std::map<std::string, Type> types;
-	std::vector<Metric> metrics;
+	std::map<std::string, Type> types;  // Ordered the same as metrics.
+	std::map<MetricKey, Metric> metrics;
+	std::vector<Histogram> histograms;
+
+	friend class Histogram;
+};
+
+class Histogram {
+public:
+	void init(const std::vector<double> &bucket_vals);
+	void init_uniform(size_t num_buckets);  // Sets up buckets 0..(N-1).
+	void init_geometric(double min, double max, size_t num_buckets);
+	void count_event(double val);
+	std::string serialize(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels) const;
+
+private:
+	// Bucket <i> counts number of events where val[i - 1] < x <= val[i].
+	// The end histogram ends up being made into a cumulative one,
+	// but that's not how we store it here.
+	struct Bucket {
+		double val;
+		std::atomic<int64_t> count{0};
+	};
+	std::unique_ptr<Bucket[]> buckets;
+	size_t num_buckets;
+	std::atomic<double> sum{0.0};
+	std::atomic<int64_t> count_after_last_bucket{0};
 };
 
 extern Metrics global_metrics;