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231 lines (198 loc) · 6.07 KB
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#ifndef SRC_HISTOGRAM_INL_H_
#define SRC_HISTOGRAM_INL_H_
#if defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
#include "histogram.h"
#include "base_object-inl.h"
#include "node_internals.h"
namespace node {
void Histogram::UpdateEwma(double value) {
// Called inside a write lock. No-op when EWMA is disabled.
if (ewma_alpha_ <= 0) return;
if (!ewma_initialized_) {
ewma_mean_ = value;
ewma_variance_ = 0;
ewma_initialized_ = true;
if (threshold_ > 0) {
ewma_error_rate_ = (value > static_cast<double>(threshold_)) ? 1.0 : 0.0;
}
return;
}
double diff = value - ewma_mean_;
ewma_mean_ += ewma_alpha_ * diff;
ewma_variance_ =
(1.0 - ewma_alpha_) * (ewma_variance_ + ewma_alpha_ * diff * diff);
// Binary EWMA for SLO error rate: feed 1 if over threshold, 0 otherwise.
if (threshold_ > 0) {
double exceeded = (value > static_cast<double>(threshold_)) ? 1.0 : 0.0;
ewma_error_rate_ += ewma_alpha_ * (exceeded - ewma_error_rate_);
}
}
void Histogram::InvalidateRecordedSnapshot() {
mutation_generation_++;
recorded_snapshot_cache_.reset();
}
void Histogram::Reset() {
RwLock::ScopedWriteLock lock(mutex_);
hdr_reset(histogram_.get());
InvalidateRecordedSnapshot();
reset_count_++;
exceeds_ = 0;
prev_ = 0;
ewma_mean_ = 0;
ewma_variance_ = 0;
ewma_error_rate_ = 0;
ewma_initialized_ = false;
}
double Histogram::Add(const Histogram& other) {
auto do_add = [&]() {
exceeds_ += other.exceeds_;
if (other.prev_ > prev_) prev_ = other.prev_;
// hdr_add merges all bucket counts and total_count internally.
const double dropped =
static_cast<double>(hdr_add(histogram_.get(), other.histogram_.get()));
InvalidateRecordedSnapshot();
return dropped;
};
// When adding a histogram to itself, a single write lock suffices.
if (this == &other) {
RwLock::ScopedWriteLock lock(mutex_);
return do_add();
}
// Write-lock this (modified), read-lock other (only read).
// Lock in pointer order to prevent deadlock.
if (this < &other) {
RwLock::ScopedWriteLock lock1(mutex_);
RwLock::ScopedReadLock lock2(other.mutex_);
return do_add();
}
RwLock::ScopedReadLock lock1(other.mutex_);
RwLock::ScopedWriteLock lock2(mutex_);
return do_add();
}
size_t Histogram::Count() const {
RwLock::ScopedReadLock lock(mutex_);
return static_cast<size_t>(histogram_->total_count);
}
size_t Histogram::Exceeds() const {
RwLock::ScopedReadLock lock(mutex_);
return exceeds_;
}
uint64_t Histogram::ResetCount() const {
RwLock::ScopedReadLock lock(mutex_);
return reset_count_;
}
int64_t Histogram::Min() const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_min(histogram_.get());
}
int64_t Histogram::Max() const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_max(histogram_.get());
}
double Histogram::Mean() const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_mean(histogram_.get());
}
double Histogram::Stddev() const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_stddev(histogram_.get());
}
double Histogram::EwmaMean() const {
RwLock::ScopedReadLock lock(mutex_);
return ewma_initialized_ ? ewma_mean_ : 0;
}
double Histogram::EwmaStddev() const {
RwLock::ScopedReadLock lock(mutex_);
return ewma_initialized_ ? std::sqrt(ewma_variance_) : 0;
}
double Histogram::EwmaErrorRate() const {
RwLock::ScopedReadLock lock(mutex_);
return ewma_initialized_ ? ewma_error_rate_ : 0;
}
int64_t Histogram::Percentile(double percentile) const {
RwLock::ScopedReadLock lock(mutex_);
CHECK_GT(percentile, 0);
CHECK_LE(percentile, 100);
return hdr_value_at_percentile(histogram_.get(), percentile);
}
template <typename Iterator>
void Histogram::Percentiles(Iterator&& fn) const {
RwLock::ScopedReadLock lock(mutex_);
hdr_iter iter;
hdr_iter_percentile_init(&iter, histogram_.get(), 1);
while (hdr_iter_next(&iter)) {
double key = iter.specifics.percentiles.percentile;
fn(key, iter.value);
}
}
int64_t Histogram::CountAt(int64_t value) const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_count_at_value(histogram_.get(), value);
}
bool Histogram::RecordCorrected(int64_t value, int64_t expected_interval) {
RwLock::ScopedWriteLock lock(mutex_);
bool recorded =
hdr_record_corrected_value(histogram_.get(), value, expected_interval);
if (!recorded)
exceeds_++;
else {
InvalidateRecordedSnapshot();
UpdateEwma(static_cast<double>(value));
}
return recorded;
}
bool Histogram::Record(int64_t value) {
RwLock::ScopedWriteLock lock(mutex_);
bool recorded = hdr_record_value(histogram_.get(), value);
if (!recorded)
exceeds_++;
else {
InvalidateRecordedSnapshot();
UpdateEwma(static_cast<double>(value));
}
return recorded;
}
uint64_t Histogram::RecordDelta() {
RwLock::ScopedWriteLock lock(mutex_);
uint64_t time = uv_hrtime();
int64_t delta = 0;
if (prev_ > 0) {
CHECK_GE(time, prev_);
delta = time - prev_;
if (!hdr_record_value(histogram_.get(), delta))
exceeds_++;
else {
InvalidateRecordedSnapshot();
UpdateEwma(static_cast<double>(delta));
}
}
prev_ = time;
return delta;
}
size_t Histogram::GetMemorySize() const {
RwLock::ScopedReadLock lock(mutex_);
return hdr_get_memory_size(histogram_.get());
}
template <typename Iterator>
void Histogram::LinearBuckets(int64_t step_size, Iterator&& fn) const {
RwLock::ScopedReadLock lock(mutex_);
hdr_iter iter;
hdr_iter_linear_init(&iter, histogram_.get(), step_size);
while (hdr_iter_next(&iter)) {
fn(iter.value, iter.specifics.linear.count_added_in_this_iteration_step);
}
}
template <typename Iterator>
void Histogram::LogBuckets(int64_t first_bucket,
double log_base,
Iterator&& fn) const {
RwLock::ScopedReadLock lock(mutex_);
hdr_iter iter;
hdr_iter_log_init(&iter, histogram_.get(), first_bucket, log_base);
while (hdr_iter_next(&iter)) {
fn(iter.value, iter.specifics.log.count_added_in_this_iteration_step);
}
}
} // namespace node
#endif // defined(NODE_WANT_INTERNALS) && NODE_WANT_INTERNALS
#endif // SRC_HISTOGRAM_INL_H_