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/**
* Copyright (C) 2022-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 <array>
#include <boost/optional.hpp>
#include <fmt/format.h>
#include "mongo/base/string_data.h"
#include "mongo/bson/bsonobjbuilder.h"
#include "mongo/logv2/log.h"
#include "mongo/util/duration.h"
#include "mongo/util/timer.h"
#define MONGO_LOGV2_DEFAULT_COMPONENT ::mongo::logv2::LogComponent::kNetwork
namespace mongo {
namespace split_timer_detail {
/**
* Takes an invokable `f` and a pack of optionals `as...`.
* Invokes `f(*as...)`, returning the result as an optional.
* If any of `as...` are disengaged, then `f` is not
* invoked, and a disengaged result is returned.
*/
template <typename F,
typename... As,
typename R = std::invoke_result_t<F, decltype(*std::declval<As>())...>>
boost::optional<R> applyViaOptionals(F&& f, As&&... as) {
if (!(as && ...))
return {};
return std::invoke(f, *as...);
}
/** Rule of Zero utility. Starts true, becomes false when moved from or dismissed. */
class UniqueActive {
public:
UniqueActive() = default;
UniqueActive(UniqueActive&& other) noexcept : _active{other.dismiss()} {}
UniqueActive& operator=(UniqueActive&& other) noexcept {
if (this != &other)
_active = other.dismiss();
return *this;
}
explicit operator bool() const {
return _active;
}
/** Returns true if dismiss changed this object's state. */
bool dismiss() {
return std::exchange(_active, false);
}
private:
bool _active = true;
};
} // namespace split_timer_detail
/**
* Acts as a split timer which captures times elapsed at various points throughout a single
* SessionWorkflow loop. The SessionWorkflow loop is expected to construct this
* object when timing should begin, call this object's `notify` function at
* appropriate times throughout the workflow, and destroy it when the loop work is done.
*
* Requirements on Policy:
* - TimeSplitIdType and IntervalIdType packed enums.
* - static constexpr properties:
* - size_t numIntervalIds and numTimesplitIds for enum extents.
* - toIdx(e) to convert these enums to size_t.
* - getName(e) to convert these enums to StringData (intervals should end in "Millis").
* - TimeSplitIdType getStartSplit(IntervalIdType).
* - TimeSplitIdType getEndSplit(IntervalIdType).
* - nonstatic onStart and onFinish member functions, taking a pointer to this SplitTimer.
* - nonstatic makeTimer to initialize Timer.
*/
template <typename Policy>
class SplitTimer {
private:
template <typename E>
static constexpr size_t _idx(E e) {
return Policy::toIdx(e);
}
public:
using TimeSplitIdType = typename Policy::TimeSplitIdType;
using IntervalIdType = typename Policy::IntervalIdType;
SplitTimer() : SplitTimer{Policy{}} {}
SplitTimer(Policy policy) : _policy{std::move(policy)} {
_policy.onStart(this);
}
SplitTimer& operator=(SplitTimer&&) = default;
SplitTimer(SplitTimer&&) = default;
/**
* Idempotent: if already inactive (moved-from), does nothing.
* If active: sets to inactive, captures the elapsed time for the `done`
* TimeSplitId, logs any necessary metrics.
*/
~SplitTimer() {
if (!_active)
return;
_policy.onFinish(this);
}
/**
* Captures the elapsed time and associates it with `split`. A second call with the same `split`
* will overwrite the previous. It is expected that this gets called for all splits other than
* TimerSplit::start and TimerSplit::done.
*/
void notify(TimeSplitIdType split) {
using namespace fmt::literals;
invariant(!_topSplit || _idx(*_topSplit) <= _idx(split),
"Notify out of order: {} then {}"_format(_policy.getName(*_topSplit),
_policy.getName(split)));
_topSplit = split;
_splits[_idx(split)] = _timer.elapsed();
}
/**
* Returns the time elapsed between the two splits corresponding to `start` and `end`.
* If either is disengaged, a disengaged optional will be returned.
*/
boost::optional<Microseconds> getSplitInterval(IntervalIdType id) const {
return split_timer_detail::applyViaOptionals(std::minus<>{},
_splits[_idx(_policy.getEndSplit(id))],
_splits[_idx(_policy.getStartSplit(id))]);
}
/**
* Appends the intervals defined in Policy::intervalDefs to `builder`.
* Logs the whole builder if there's a problem.
*/
void appendIntervals(BSONObjBuilder& builder) const {
using namespace fmt::literals;
for (size_t i = 0; i != Policy::numIntervalIds; ++i) {
IntervalIdType iId{i};
auto dt = getSplitInterval(iId);
if (!dt)
continue;
if (*dt < Microseconds{0})
LOGV2_FATAL(6983001,
"Negative time interval",
"dt"_attr = dt->toString(),
"splits"_attr = _splitsToBSON());
builder.append(_policy.getName(iId), durationCount<Milliseconds>(*dt));
}
}
private:
using SplitsArray = std::array<boost::optional<Microseconds>, Policy::numTimeSplitIds>;
BSONObj _splitsToBSON() const {
BSONObjBuilder bob;
for (size_t i = 0; i != Policy::numTimeSplitIds; ++i) {
TimeSplitIdType ts{i};
auto&& t = _splits[_idx(ts)];
bob.append(_policy.getName(ts), t ? t->toString() : "");
}
return bob.obj();
}
Policy _policy;
split_timer_detail::UniqueActive _active;
Timer _timer = _policy.makeTimer();
SplitsArray _splits;
boost::optional<TimeSplitIdType> _topSplit;
};
} // namespace mongo
#undef MONGO_LOGV2_DEFAULT_COMPONENT
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