git.sesse.net Git - nageru/blob - metrics.cpp

   1 #include "metrics.h"
   2
   3 #include <assert.h>
   4 #include <math.h>
   5
   6 #include <algorithm>
   7 #include <chrono>
   8 #include <locale>
   9 #include <sstream>
  10
  11 using namespace std;
  12 using namespace std::chrono;
  13
  14 Metrics global_metrics;
  15
  16 double get_timestamp_for_metrics()
  17 {
  18         return duration<double>(system_clock::now().time_since_epoch()).count();
  19 }
  20
  21 string Metrics::serialize_name(const string &name, const vector<pair<string, string>> &labels)
  22 {
  23         return "nageru_" + name + serialize_labels(labels);
  24 }
  25
  26 string Metrics::serialize_labels(const vector<pair<string, string>> &labels)
  27 {
  28         if (labels.empty()) {
  29                 return "";
  30         }
  31
  32         string label_str;
  33         for (const pair<string, string> &label : labels) {
  34                 if (!label_str.empty()) {
  35                         label_str += ",";
  36                 }
  37                 label_str += label.first + "=\"" + label.second + "\"";
  38         }
  39         return "{" + label_str + "}";
  40 }
  41
  42 void Metrics::add(const string &name, const vector<pair<string, string>> &labels, atomic<int64_t> *location, Metrics::Type type)
  43 {
  44         Metric metric;
  45         metric.data_type = DATA_TYPE_INT64;
  46         metric.location_int64 = location;
  47
  48         lock_guard<mutex> lock(mu);
  49         metrics.emplace(MetricKey(name, labels), metric);
  50         assert(types.count(name) == 0 || types[name] == type);
  51         types[name] = type;
  52 }
  53
  54 void Metrics::add(const string &name, const vector<pair<string, string>> &labels, atomic<double> *location, Metrics::Type type)
  55 {
  56         Metric metric;
  57         metric.data_type = DATA_TYPE_DOUBLE;
  58         metric.location_double = location;
  59
  60         lock_guard<mutex> lock(mu);
  61         metrics.emplace(MetricKey(name, labels), metric);
  62         assert(types.count(name) == 0 || types[name] == type);
  63         types[name] = type;
  64 }
  65
  66 void Metrics::add(const string &name, const vector<pair<string, string>> &labels, Histogram *location, Laziness laziness)
  67 {
  68         Metric metric;
  69         metric.data_type = DATA_TYPE_HISTOGRAM;
  70         metric.laziness = laziness;
  71         metric.location_histogram = location;
  72
  73         lock_guard<mutex> lock(mu);
  74         metrics.emplace(MetricKey(name, labels), metric);
  75         assert(types.count(name) == 0 || types[name] == TYPE_HISTOGRAM);
  76         types[name] = TYPE_HISTOGRAM;
  77 }
  78
  79 void Metrics::add(const string &name, const vector<pair<string, string>> &labels, Summary *location, Laziness laziness)
  80 {
  81         Metric metric;
  82         metric.data_type = DATA_TYPE_SUMMARY;
  83         metric.laziness = laziness;
  84         metric.location_summary = location;
  85
  86         lock_guard<mutex> lock(mu);
  87         metrics.emplace(MetricKey(name, labels), metric);
  88         assert(types.count(name) == 0 || types[name] == TYPE_SUMMARY);
  89         types[name] = TYPE_SUMMARY;
  90 }
  91
  92 void Metrics::remove(const string &name, const vector<pair<string, string>> &labels)
  93 {
  94         lock_guard<mutex> lock(mu);
  95
  96         auto it = metrics.find(MetricKey(name, labels));
  97         assert(it != metrics.end());
  98
  99         // If this is the last metric with this name, remove the type as well.
 100         if (!((it != metrics.begin() && prev(it)->first.name == name) ||
 101               (it != metrics.end() && next(it)->first.name == name))) {
 102                 types.erase(name);
 103         }
 104
 105         metrics.erase(it);
 106 }
 107
 108 string Metrics::serialize() const
 109 {
 110         stringstream ss;
 111         ss.imbue(locale("C"));
 112         ss.precision(20);
 113
 114         lock_guard<mutex> lock(mu);
 115         auto type_it = types.cbegin();
 116         for (const auto &key_and_metric : metrics) {
 117                 string name = "nageru_" + key_and_metric.first.name + key_and_metric.first.serialized_labels;
 118                 const Metric &metric = key_and_metric.second;
 119
 120                 if (type_it != types.cend() &&
 121                     key_and_metric.first.name == type_it->first) {
 122                         // It's the first time we print out any metric with this name,
 123                         // so add the type header.
 124                         if (type_it->second == TYPE_GAUGE) {
 125                                 ss << "# TYPE nageru_" << type_it->first << " gauge\n";
 126                         } else if (type_it->second == TYPE_HISTOGRAM) {
 127                                 ss << "# TYPE nageru_" << type_it->first << " histogram\n";
 128                         } else if (type_it->second == TYPE_SUMMARY) {
 129                                 ss << "# TYPE nageru_" << type_it->first << " summary\n";
 130                         }
 131                         ++type_it;
 132                 }
 133
 134                 if (metric.data_type == DATA_TYPE_INT64) {
 135                         ss << name << " " << metric.location_int64->load() << "\n";
 136                 } else if (metric.data_type == DATA_TYPE_DOUBLE) {
 137                         double val = metric.location_double->load();
 138                         if (isnan(val)) {
 139                                 // Prometheus can't handle “-nan”.
 140                                 ss << name << " NaN\n";
 141                         } else {
 142                                 ss << name << " " << val << "\n";
 143                         }
 144                 } else if (metric.data_type == DATA_TYPE_HISTOGRAM) {
 145                         ss << metric.location_histogram->serialize(metric.laziness, key_and_metric.first.name, key_and_metric.first.labels);
 146                 } else {
 147                         ss << metric.location_summary->serialize(metric.laziness, key_and_metric.first.name, key_and_metric.first.labels);
 148                 }
 149         }
 150
 151         return ss.str();
 152 }
 153
 154 void Histogram::init(const vector<double> &bucket_vals)
 155 {
 156         this->num_buckets = bucket_vals.size();
 157         buckets.reset(new Bucket[num_buckets]);
 158         for (size_t i = 0; i < num_buckets; ++i) {
 159                 buckets[i].val = bucket_vals[i];
 160         }
 161 }
 162
 163 void Histogram::init_uniform(size_t num_buckets)
 164 {
 165         this->num_buckets = num_buckets;
 166         buckets.reset(new Bucket[num_buckets]);
 167         for (size_t i = 0; i < num_buckets; ++i) {
 168                 buckets[i].val = i;
 169         }
 170 }
 171
 172 void Histogram::init_geometric(double min, double max, size_t num_buckets)
 173 {
 174         this->num_buckets = num_buckets;
 175         buckets.reset(new Bucket[num_buckets]);
 176         for (size_t i = 0; i < num_buckets; ++i) {
 177                 buckets[i].val = min * pow(max / min, double(i) / (num_buckets - 1));
 178         }
 179 }
 180
 181 void Histogram::count_event(double val)
 182 {
 183         Bucket ref_bucket;
 184         ref_bucket.val = val;
 185         auto it = lower_bound(buckets.get(), buckets.get() + num_buckets, ref_bucket,
 186                 [](const Bucket &a, const Bucket &b) { return a.val < b.val; });
 187         if (it == buckets.get() + num_buckets) {
 188                 ++count_after_last_bucket;
 189         } else {
 190                 ++it->count;
 191         }
 192         // Non-atomic add, but that's fine, since there are no concurrent writers.
 193         sum = sum + val;
 194 }
 195
 196 string Histogram::serialize(Metrics::Laziness laziness, const string &name, const vector<pair<string, string>> &labels) const
 197 {
 198         // Check if the histogram is empty and should not be serialized.
 199         if (laziness == Metrics::PRINT_WHEN_NONEMPTY && count_after_last_bucket.load() == 0) {
 200                 bool empty = true;
 201                 for (size_t bucket_idx = 0; bucket_idx < num_buckets; ++bucket_idx) {
 202                         if (buckets[bucket_idx].count.load() != 0) {
 203                                 empty = false;
 204                                 break;
 205                         }
 206                 }
 207                 if (empty) {
 208                         return "";
 209                 }
 210         }
 211
 212         stringstream ss;
 213         ss.imbue(locale("C"));
 214         ss.precision(20);
 215
 216         int64_t count = 0;
 217         for (size_t bucket_idx = 0; bucket_idx < num_buckets; ++bucket_idx) {
 218                 stringstream le_ss;
 219                 le_ss.imbue(locale("C"));
 220                 le_ss.precision(20);
 221                 le_ss << buckets[bucket_idx].val;
 222                 vector<pair<string, string>> bucket_labels = labels;
 223                 bucket_labels.emplace_back("le", le_ss.str());
 224
 225                 count += buckets[bucket_idx].count.load();
 226                 ss << Metrics::serialize_name(name + "_bucket", bucket_labels) << " " << count << "\n";
 227         }
 228
 229         count += count_after_last_bucket.load();
 230
 231         ss << Metrics::serialize_name(name + "_sum", labels) << " " << sum.load() << "\n";
 232         ss << Metrics::serialize_name(name + "_count", labels) << " " << count << "\n";
 233
 234         return ss.str();
 235 }
 236
 237 void Summary::init(const vector<double> &quantiles, double window_seconds)
 238 {
 239         this->quantiles = quantiles;
 240         window = duration<double>(window_seconds);
 241 }
 242
 243 void Summary::count_event(double val)
 244 {
 245         steady_clock::time_point now = steady_clock::now();
 246         steady_clock::time_point cutoff = now - duration_cast<steady_clock::duration>(window);
 247
 248         lock_guard<mutex> lock(mu);
 249         values.emplace_back(now, val);
 250         while (!values.empty() && values.front().first < cutoff) {
 251                 values.pop_front();
 252         }
 253
 254         // Non-atomic add, but that's fine, since there are no concurrent writers.
 255         sum = sum + val;
 256         ++count;
 257 }
 258
 259 string Summary::serialize(Metrics::Laziness laziness, const string &name, const vector<pair<string, string>> &labels)
 260 {
 261         steady_clock::time_point now = steady_clock::now();
 262         steady_clock::time_point cutoff = now - duration_cast<steady_clock::duration>(window);
 263
 264         vector<double> values_copy;
 265         {
 266                 lock_guard<mutex> lock(mu);
 267                 while (!values.empty() && values.front().first < cutoff) {
 268                         values.pop_front();
 269                 }
 270                 values_copy.reserve(values.size());
 271                 for (const auto &time_and_value : values) {
 272                         values_copy.push_back(time_and_value.second);
 273                 }
 274         }
 275
 276         vector<pair<double, double>> answers;
 277         if (values_copy.size() == 0) {
 278                 if (laziness == Metrics::PRINT_WHEN_NONEMPTY) {
 279                         return "";
 280                 }
 281                 for (double quantile : quantiles) {
 282                         answers.emplace_back(quantile, 0.0 / 0.0);
 283                 }
 284         } else if (values_copy.size() == 1) {
 285                 for (double quantile : quantiles) {
 286                         answers.emplace_back(quantile, values_copy[0]);
 287                 }
 288         } else {
 289                 // We could probably do repeated nth_element, but the constant factor
 290                 // gets a bit high, so just sorting probably is about as fast.
 291                 sort(values_copy.begin(), values_copy.end());
 292                 for (double quantile : quantiles) {
 293                         double idx = quantile * (values_copy.size() - 1);
 294                         size_t idx_floor = size_t(floor(idx));
 295                         const double v0 = values_copy[idx_floor];
 296
 297                         if (idx_floor == values_copy.size() - 1) {
 298                                 answers.emplace_back(quantile, values_copy[idx_floor]);
 299                         } else {
 300                                 // Linear interpolation.
 301                                 double t = idx - idx_floor;
 302                                 const double v1 = values_copy[idx_floor + 1];
 303                                 answers.emplace_back(quantile, v0 + t * (v1 - v0));
 304                         }
 305                 }
 306         }
 307
 308         stringstream ss;
 309         ss.imbue(locale("C"));
 310         ss.precision(20);
 311
 312         for (const auto &quantile_and_value : answers) {
 313                 stringstream quantile_ss;
 314                 quantile_ss.imbue(locale("C"));
 315                 quantile_ss.precision(3);
 316                 quantile_ss << quantile_and_value.first;
 317                 vector<pair<string, string>> quantile_labels = labels;
 318                 quantile_labels.emplace_back("quantile", quantile_ss.str());
 319
 320                 double val = quantile_and_value.second;;
 321                 if (isnan(val)) {
 322                         // Prometheus can't handle “-nan”.
 323                         ss << Metrics::serialize_name(name, quantile_labels) << " NaN\n";
 324                 } else {
 325                         ss << Metrics::serialize_name(name, quantile_labels) << " " << val << "\n";
 326                 }
 327         }
 328
 329         ss << Metrics::serialize_name(name + "_sum", labels) << " " << sum.load() << "\n";
 330         ss << Metrics::serialize_name(name + "_count", labels) << " " << count.load() << "\n";
 331         return ss.str();
 332 }