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/**
* Copyright (C) 2021-present MongoDB, Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the Server Side Public License, version 1,
* as published by MongoDB, Inc.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* Server Side Public License for more details.
*
* You should have received a copy of the Server Side Public License
* along with this program. If not, see
* <http://www.mongodb.com/licensing/server-side-public-license>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the Server Side Public License in all respects for
* all of the code used other than as permitted herein. If you modify file(s)
* with this exception, you may extend this exception to your version of the
* file(s), but you are not obligated to do so. If you do not wish to do so,
* delete this exception statement from your version. If you delete this
* exception statement from all source files in the program, then also delete
* it in the license file.
*/
#pragma once
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/db/commands.h"
#include <vector>
namespace mongo {
/**
* Generalized version of OperationLatencyHistogram that can track latencies for any operation type
* with custom lower bounds. For some provided lower bounds {x,y} a number z will be counted in the
* x-y bucket if z ∈ [x, y). in the y-inf bucket if z ∈ [y, inf). and in the (-inf, x) bucket if z <
* x.
*/
template <std::size_t numLowerBounds>
class IntegerHistogram {
public:
const std::string kKey;
IntegerHistogram(std::string key, std::array<int64_t, numLowerBounds> lowerBounds)
: kKey(std::move(key)) {
invariant(!lowerBounds.empty(), "Lower bounds must not be empty");
_lowerBoundBuckets[0].lowerBound = std::numeric_limits<int64_t>::min();
int64_t prevVal = std::numeric_limits<int64_t>::min();
for (size_t i = 1; i < _lowerBoundBuckets.size(); ++i) {
auto lowerBoundVal = lowerBounds.at(i - 1);
invariant(lowerBoundVal > prevVal,
"Lower bounds must be strictly monotonically increasing");
_lowerBoundBuckets[i].lowerBound = lowerBoundVal;
prevVal = lowerBoundVal;
}
}
void append(BSONObjBuilder& builder, bool shouldAppendAdditionalInfo) const {
BSONObjBuilder histogramBuilder(builder.subobjStart(kKey));
auto offsetToString = [this](size_t offset) {
if (offset == 0)
return std::string("-inf");
if (offset < _lowerBoundBuckets.size())
return std::to_string(_lowerBoundBuckets[offset].lowerBound);
return std::string("inf");
};
for (size_t i = 0; i < _lowerBoundBuckets.size(); i++) {
auto count = _lowerBoundBuckets[i].count.load();
if (count == 0)
continue;
auto key = fmt::format("{} - {}", offsetToString(i), offsetToString(i + 1));
BSONObjBuilder entryBuilder(histogramBuilder.subobjStart(key));
entryBuilder.append("count", (long long)(count));
entryBuilder.doneFast();
}
auto totalCount = _entryCount.load();
histogramBuilder.append("ops", (long long)totalCount);
if (shouldAppendAdditionalInfo && totalCount != 0) {
auto sum = _sum.load();
histogramBuilder.append("sum", (long long)sum);
histogramBuilder.append("mean", static_cast<double>(sum) / totalCount);
}
histogramBuilder.doneFast();
}
void increment(int64_t data) {
auto insertionIndex = std::upper_bound(_lowerBoundBuckets.begin(),
_lowerBoundBuckets.end(),
data,
[](const int64_t a, const LowerBoundBucket& b) {
return a < b.lowerBound;
}) -
1;
insertionIndex->count.addAndFetch(1);
_entryCount.addAndFetch(1);
_sum.addAndFetch(data);
}
private:
struct LowerBoundBucket {
int64_t lowerBound;
AtomicWord<int64_t> count;
};
std::array<LowerBoundBucket, numLowerBounds + 1> _lowerBoundBuckets;
AtomicWord<int64_t> _entryCount;
AtomicWord<int64_t> _sum;
};
} // namespace mongo
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