// which makes it quite unwieldy. Thus, we'll package our own for the time being.
#include <atomic>
+#include <chrono>
+#include <deque>
+#include <map>
+#include <memory>
#include <mutex>
#include <string>
-#include <unordered_map>
+#include <utility>
+#include <vector>
+
+class Histogram;
+class Summary;
+
+// 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.
+ TYPE_SUMMARY, // Internal use only.
};
+ enum Laziness {
+ PRINT_ALWAYS,
+ PRINT_WHEN_NONEMPTY,
+ };
+
+ void add(const std::string &name, std::atomic<int64_t> *location, Type type = TYPE_COUNTER)
+ {
+ add(name, {}, location, type);
+ }
+
+ void add(const std::string &name, std::atomic<double> *location, Type type = TYPE_COUNTER)
+ {
+ add(name, {}, location, type);
+ }
+
+ void add(const std::string &name, Histogram *location)
+ {
+ add(name, {}, location);
+ }
+
+ void add(const std::string &name, Summary *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, Laziness laziness = PRINT_ALWAYS);
+ void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, Summary *location, Laziness laziness = PRINT_ALWAYS);
+
+ void remove(const std::string &name)
+ {
+ remove(name, {});
+ }
+
+ void remove(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels);
- void register_int_metric(const std::string &name, std::atomic<int64_t> *location, Type type = TYPE_COUNTER);
- void register_double_metric(const std::string &name, std::atomic<double> *location, Type type = TYPE_COUNTER);
std::string serialize() const;
private:
- template<class T>
+ 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,
+ DATA_TYPE_SUMMARY,
+ };
+ 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 {
- Type type;
- std::atomic<T> *location;
+ DataType data_type;
+ Laziness laziness; // Only for TYPE_HISTOGRAM.
+ union {
+ std::atomic<int64_t> *location_int64;
+ std::atomic<double> *location_double;
+ Histogram *location_histogram;
+ Summary *location_summary;
+ };
};
mutable std::mutex mu;
- std::unordered_map<std::string, Metric<int64_t>> int_metrics;
- std::unordered_map<std::string, Metric<double>> double_metrics;
+ std::map<std::string, Type> types; // Ordered the same as metrics.
+ std::map<MetricKey, Metric> metrics;
+
+ friend class Histogram;
+ friend class Summary;
+};
+
+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(Metrics::Laziness laziness, 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};
+};
+
+// This is a pretty dumb streaming quantile class, but it's exact, and we don't have
+// too many values (typically one per frame, and one-minute interval), so we don't
+// need anything fancy.
+class Summary {
+public:
+ void init(const std::vector<double> &quantiles, double window_seconds);
+ void count_event(double val);
+ std::string serialize(Metrics::Laziness laziness, const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels);
+
+private:
+ std::vector<double> quantiles;
+ std::chrono::duration<double> window;
+
+ mutable std::mutex mu;
+ std::deque<std::pair<std::chrono::steady_clock::time_point, double>> values;
+ std::atomic<double> sum{0.0};
+ std::atomic<int64_t> count{0};
};
extern Metrics global_metrics;