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/**
* Copyright (C) 2019-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/logger/log_severity.h"
#include "mongo/logger/logstream_builder.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/unordered_map.h"
#include "mongo/util/time_support.h"
namespace mongo::logger {
/**
* A thread-safe widget to chose a lower severity for a given key once every T milliseconds.
*
* Note that this class is thread-safe but not global. You must maintain an instance to preserve the
* Date_t for the last time you were given the "limited" severity instead of the "normal" severity.
* The recommended method for this style of lifetime extension is via a static local variable.
* The MONGO_GET_LIMITED_SEVERITY macro below provides a relatively painless way to get the
* appropriate severity out of a LogSeverityLimiter initialized as a static local variable in a
* contained block scope.
*/
template <typename KeyT>
class LogSeverityLimiter {
public:
static constexpr auto kDefaultPeriod = Seconds{1};
static constexpr auto kDefaultLimitedDLevel = 0;
static constexpr auto kDefaultNormalDLevel = 2;
public:
/**
* Construct a LogSeverityLimiter
*
* @param normalDLevel The debug level to use most of the time
* @param limitedDLevel The debug level to use at most at a specified interval
* @param period The minimum period before getLogSeverityFor returns the limited severity
* again
*/
explicit LogSeverityLimiter(Milliseconds period, int limitedDLevel, int normalDLevel)
: _period{period},
_limitedLogSeverity{LogstreamBuilder::severityCast(limitedDLevel)},
_normalLogSeverity{LogstreamBuilder::severityCast(normalDLevel)} {
// This widget has no point if limited isn't a lower verbosity than normal
invariant(limitedDLevel < normalDLevel);
}
/**
* Return the appropriate LogSeverity for the key provided at this point in time
*
* @param key The key for this series of LogSeverity. This must have a copy ctor.
*/
LogSeverity nextFor(const KeyT& key) {
auto now = Date_t::now();
stdx::lock_guard<Latch> lk(_mutex);
auto& cutoff = _cutoffByKey[key];
if (now > cutoff) {
// This means that the next log batch at this level will be at least _period
// milliseconds after this one. This does effectively skew.
cutoff = now + _period;
return _limitedLogSeverity;
}
return _normalLogSeverity;
}
private:
Milliseconds _period;
LogSeverity _limitedLogSeverity;
LogSeverity _normalLogSeverity;
Mutex _mutex = MONGO_MAKE_LATCH("LogSeverityLimiter::_mutex");
stdx::unordered_map<KeyT, Date_t> _cutoffByKey;
};
#define MONGO_GET_LIMITED_SEVERITY(KEY, PERIOD, LIMITED, NORMAL) \
[&] { \
using KeyT = std::decay_t<decltype(KEY)>; \
static auto limiter = mongo::logger::LogSeverityLimiter<KeyT>(PERIOD, LIMITED, NORMAL); \
return limiter.nextFor(KEY); \
}()
} // namespace mongo::logger
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