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histogram.cc
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histogram.cc
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#include "prometheus/histogram.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <iterator>
#include <limits>
#include <memory>
#include <stdexcept>
#include <utility>
namespace prometheus {
Histogram::Histogram(const BucketBoundaries& buckets)
: bucket_boundaries_{buckets},
bucket_counts_(buckets.size() + 1u, 0.0),
sum_{0.0} {
assert(std::is_sorted(std::begin(bucket_boundaries_),
std::end(bucket_boundaries_)));
}
void Histogram::Observe(const double value) {
// TODO: determine bucket list size at which binary search would be faster
const auto bucket_index = static_cast<std::size_t>(std::distance(
bucket_boundaries_.begin(),
std::find_if(
std::begin(bucket_boundaries_), std::end(bucket_boundaries_),
[value](const double boundary) { return boundary >= value; })));
std::lock_guard<std::mutex> lock(mutex_);
sum_ += value;
if (!(value < 0.0)) {
bucket_counts_[bucket_index]++;
}
}
void Histogram::ObserveMultiple(const std::vector<double>& bucket_increments,
const double sum_of_values) {
if (bucket_increments.size() != bucket_counts_.size()) {
throw std::length_error(
"The size of bucket_increments was not equal to"
"the number of buckets in the histogram.");
}
std::lock_guard<std::mutex> lock(mutex_);
sum_ += sum_of_values;
for (std::size_t i{0}; i < bucket_counts_.size(); ++i) {
if (!(bucket_increments[i] < 0.0)) {
bucket_counts_[i] += bucket_increments[i];
}
}
}
ClientMetric Histogram::Collect() const {
std::lock_guard<std::mutex> lock(mutex_);
auto metric = ClientMetric{};
auto cumulative_count = 0ULL;
metric.histogram.bucket.reserve(bucket_counts_.size());
for (std::size_t i{0}; i < bucket_counts_.size(); ++i) {
cumulative_count += bucket_counts_[i];
auto bucket = ClientMetric::Bucket{};
bucket.cumulative_count = cumulative_count;
bucket.upper_bound = (i == bucket_boundaries_.size()
? std::numeric_limits<double>::infinity()
: bucket_boundaries_[i]);
metric.histogram.bucket.push_back(std::move(bucket));
}
metric.histogram.sample_count = cumulative_count;
metric.histogram.sample_sum = sum_;
return metric;
}
} // namespace prometheus