+
+void Histogram::init(const vector<double> &bucket_vals)
+{
+ this->num_buckets = bucket_vals.size();
+ buckets.reset(new Bucket[num_buckets]);
+ for (size_t i = 0; i < num_buckets; ++i) {
+ buckets[i].val = bucket_vals[i];
+ }
+}
+
+void Histogram::init_uniform(size_t num_buckets)
+{
+ this->num_buckets = num_buckets;
+ buckets.reset(new Bucket[num_buckets]);
+ for (size_t i = 0; i < num_buckets; ++i) {
+ buckets[i].val = i;
+ }
+}
+
+void Histogram::init_geometric(double min, double max, size_t num_buckets)
+{
+ this->num_buckets = num_buckets;
+ buckets.reset(new Bucket[num_buckets]);
+ for (size_t i = 0; i < num_buckets; ++i) {
+ buckets[i].val = min * pow(max / min, double(i) / (num_buckets - 1));
+ }
+}
+
+void Histogram::count_event(double val)
+{
+ Bucket ref_bucket;
+ ref_bucket.val = val;
+ auto it = lower_bound(buckets.get(), buckets.get() + num_buckets, ref_bucket,
+ [](const Bucket &a, const Bucket &b) { return a.val < b.val; });
+ if (it == buckets.get() + num_buckets) {
+ ++count_after_last_bucket;
+ } else {
+ ++it->count;
+ }
+ // Non-atomic add, but that's fine, since there are no concurrent writers.
+ sum = sum + val;
+}
+
+string Histogram::serialize(const string &name, const vector<pair<string, string>> &labels) const
+{
+ stringstream ss;
+ ss.imbue(locale("C"));
+ ss.precision(20);
+
+ int64_t count = 0;
+ for (size_t bucket_idx = 0; bucket_idx < num_buckets; ++bucket_idx) {
+ stringstream le_ss;
+ le_ss.imbue(locale("C"));
+ le_ss.precision(20);
+ le_ss << buckets[bucket_idx].val;
+ vector<pair<string, string>> bucket_labels = labels;
+ bucket_labels.emplace_back("le", le_ss.str());
+
+ count += buckets[bucket_idx].count.load();
+ ss << Metrics::serialize_name(name + "_bucket", bucket_labels) << " " << count << "\n";
+ }
+
+ count += count_after_last_bucket.load();
+
+ ss << Metrics::serialize_name(name + "_sum", labels) << " " << sum.load() << "\n";
+ ss << Metrics::serialize_name(name + "_count", labels) << " " << count << "\n";
+
+ return ss.str();
+}