4 // A simple global class to keep track of metrics export in Prometheus format.
5 // It would be better to use a more full-featured Prometheus client library for this,
6 // but it would introduce a dependency that is not commonly packaged in distributions,
7 // which makes it quite unwieldy. Thus, we'll package our own for the time being.
18 // Prometheus recommends the use of timestamps instead of “time since event”,
19 // so you can use this to get the number of seconds since the epoch.
20 // Note that this will be wrong if your clock changes, so for non-metric use,
21 // you should use std::chrono::steady_clock instead.
22 double get_timestamp_for_metrics();
29 TYPE_HISTOGRAM, // Internal use only.
32 void add(const std::string &name, std::atomic<int64_t> *location, Type type = TYPE_COUNTER)
34 add(name, {}, location, type);
37 void add(const std::string &name, std::atomic<double> *location, Type type = TYPE_COUNTER)
39 add(name, {}, location, type);
42 void add(const std::string &name, Histogram *location)
44 add(name, {}, location);
47 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);
48 void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, std::atomic<double> *location, Type type = TYPE_COUNTER);
49 void add(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels, Histogram *location);
51 std::string serialize() const;
54 static std::string serialize_name(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels);
55 static std::string serialize_labels(const std::vector<std::pair<std::string, std::string>> &labels);
63 MetricKey(const std::string &name, const std::vector<std::pair<std::string, std::string>> labels)
64 : name(name), labels(labels), serialized_labels(serialize_labels(labels))
68 bool operator< (const MetricKey &other) const
70 if (name != other.name)
71 return name < other.name;
72 return serialized_labels < other.serialized_labels;
75 const std::string name;
76 const std::vector<std::pair<std::string, std::string>> labels;
77 const std::string serialized_labels;
82 std::atomic<int64_t> *location_int64;
83 std::atomic<double> *location_double;
84 Histogram *location_histogram;
88 mutable std::mutex mu;
89 std::map<std::string, Type> types; // Ordered the same as metrics.
90 std::map<MetricKey, Metric> metrics;
91 std::vector<Histogram> histograms;
93 friend class Histogram;
98 void init(const std::vector<double> &bucket_vals);
99 void init_uniform(size_t num_buckets); // Sets up buckets 0..(N-1).
100 void init_geometric(double min, double max, size_t num_buckets);
101 void count_event(double val);
102 std::string serialize(const std::string &name, const std::vector<std::pair<std::string, std::string>> &labels) const;
105 // Bucket <i> counts number of events where val[i - 1] < x <= val[i].
106 // The end histogram ends up being made into a cumulative one,
107 // but that's not how we store it here.
110 std::atomic<int64_t> count{0};
112 std::unique_ptr<Bucket[]> buckets;
114 std::atomic<double> sum{0.0};
115 std::atomic<int64_t> count_after_last_bucket{0};
118 extern Metrics global_metrics;
120 #endif // !defined(_METRICS_H)