1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
/**
* 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 <string>
#include "mongo/base/status.h"
#include "mongo/executor/task_executor.h"
#include "mongo/util/time_support.h"
namespace mongo {
namespace repl {
/**
* The DelayableTimeoutCallback is a utility class which allows a callback to be scheduled on an
* executor at a given time, and then that time pushed back (later) arbitrarily often without
* rescheduling the call on the executor. The callback is never called with CallbackCanceled or
* ShutdownInProgress.
*
* All methods are thread safe, though isActive() and getNextCall() may return stale information
* if external synchronization is not used. The callback is called without any locks held.
*/
class DelayableTimeoutCallback {
public:
/**
* Creates a DelayableTimeoutCallback with the given executor and callback function. The
* DelayableTimeoutCallback is inactive (the callback is not scheduled) when constructed.
*/
DelayableTimeoutCallback(executor::TaskExecutor* executor,
executor::TaskExecutor::CallbackFn callback,
std::string timerName = std::string())
: _executor(executor), _callback(std::move(callback)), _timerName(std::move(timerName)){};
~DelayableTimeoutCallback();
/**
* If the timeout is scheduled, cancel it. The callback function will not be called.
*/
void cancel();
/**
* Schedule the timeout to occur at "when", regardless of if or when it is already scheduled.
* If it is already scheduled to occur after "when", it is canceled and rescheduled
*
* Returns status of the attempt to schedule on the executor.
*/
Status scheduleAt(Date_t when);
/**
* Schedule the timeout to occur at "when" if it is not scheduled or scheduled to occur before
* "when". If it is already scheduled to occur before "when", this call has no effect.
*
* Returns status of the attempt to schedule on the executor.
*/
Status delayUntil(Date_t when);
/**
* Returns whether the callback is scheduled at all.
*/
bool isActive() const;
/**
* Returns when the next call to the passed-in callback will be made, or Date_t() if inactive.
*/
Date_t getNextCall() const;
protected:
void _cancel(WithLock);
Status _scheduleAt(WithLock, Date_t when);
Status _delayUntil(WithLock, Date_t when);
executor::TaskExecutor* _getExecutor() {
return _executor;
}
mutable Mutex _mutex = MONGO_MAKE_LATCH("DelayableTimeoutCallback");
private:
void _handleTimeout(const executor::TaskExecutor::CallbackArgs& cbData);
Status _reschedule(WithLock, Date_t when);
executor::TaskExecutor* _executor;
executor::TaskExecutor::CallbackHandle _cbHandle;
const executor::TaskExecutor::CallbackFn _callback;
Date_t _nextCall;
// Timer name is used only for logging.
const std::string _timerName;
};
/**
* DelayableTimeoutCallbackWithJitter is a slight variation on DelayableTimeoutCallback
* which adds some additional random time to delays. Since the callback may be delayed at
* intervals much shorter than the random time, this would naively result in the timeout
* either being moved backwards often, or if we forbid moving it backwards, ending up quickly
* moving to the maximum jitter (which isn't very random). To avoid that, we only recompute
* the jitter every maximum jitter interval -- e.g. if the max jitter is 10 seconds and we
* add 3 seconds jitter at time T, we will add 3 seconds jitter to every subsequent call until
* time T + 10.
*
* The typical purpose of the jitter is to prevent two timers receiving delay calls at the same
* times from firing at the same time.
*
* Synchronization of the randomSource is up to the caller; it is provided externally to
* avoid having a separate random number generator per timer. The randomSource function will
* be called with the maximum jitter value passed to delayUntilWithJitter; it should return
* a value in the range [0, maxJitter) or [0, maxJitter] depending on what you want the
* actual jitter range to be.
*/
class DelayableTimeoutCallbackWithJitter : public DelayableTimeoutCallback {
public:
using RandomSource = std::function<int64_t(int64_t)>;
DelayableTimeoutCallbackWithJitter(executor::TaskExecutor* executor,
executor::TaskExecutor::CallbackFn callback,
RandomSource randomSource,
std::string timerName = std::string())
: DelayableTimeoutCallback(executor, std::move(callback), timerName),
_randomSource(std::move(randomSource)) {}
Status scheduleAt(Date_t when);
Status delayUntil(Date_t when);
Status delayUntilWithJitter(Date_t when, Milliseconds maxJitter);
private:
void _resetRandomization(WithLock);
RandomSource _randomSource;
Date_t _lastRandomizationTime;
Milliseconds _currentJitter;
};
} // namespace repl
} // namespace mongo
|
