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
|
/**
* Copyright (C) 2018-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 <boost/optional.hpp>
#include <functional>
#include "mongo/stdx/mutex.h"
#include "mongo/util/assert_util.h"
namespace mongo {
namespace repl {
/**
* RAII type that stores the result of callbacks written using the executor::TaskExecutor framework.
* Only the first result passed to setResultAndCancelRemainingWork_inlock() is saved.
* Calls '_onCompletion' on destruction with result.
* We use an invariant to ensure that a result has been provided by the caller at destruction.
*/
template <typename Result>
class CallbackCompletionGuard {
public:
/**
* Function to cancel remaining work in caller after setting '_result'.
* This function must be called while holding a lock on the caller's mutex.
*/
using CancelRemainingWorkInLockFn = std::function<void()>;
/**
* Callback function to pass result to caller at destruction.
*/
typedef std::function<void(const Result& result)> OnCompletionFn;
/**
* Constructor for this completion guard.
* 'cancelRemainingWorkInLock' is called after setting the result to cancel any outstanding
* work in the caller. 'cancelRemainingWorkInLock' must be called while holding a lock on the
* caller's mutex.
* 'onCompletion' is called with the result at destruction.
*/
CallbackCompletionGuard(const CancelRemainingWorkInLockFn& cancelRemainingWorkInLock,
const OnCompletionFn& onCompletion);
/**
* Invokes '_onCompletion' with the result.
* Aborts if:
* result is not set; or
* '_onCompletion' throws an exception.
*/
~CallbackCompletionGuard();
/**
* Sets result if called for the first time.
* Cancels remaining work in caller.
* Requires either a unique_lock or lock_guard to be passed in to ensure that we call
* _cancelRemainingWork_inlock()) while we have a lock on the callers's mutex.
*/
void setResultAndCancelRemainingWork_inlock(const stdx::lock_guard<stdx::mutex>& lock,
const Result& result);
void setResultAndCancelRemainingWork_inlock(const stdx::unique_lock<stdx::mutex>& lock,
const Result& result);
private:
/**
* Once we verified that we have the caller's lock, this function is called by both
* versions of setResultAndCancelRemainingWork_inlock() to set the result and cancel any
* remaining work in the caller.
*/
void _setResultAndCancelRemainingWork_inlock(const Result& result);
// Called at most once after setting '_result'.
const CancelRemainingWorkInLockFn _cancelRemainingWorkInLock;
// Called at destruction with '_result'.
const OnCompletionFn _onCompletion;
// _result is guarded by the mutex of the caller instance that owns this guard object.
boost::optional<Result> _result;
};
template <typename Result>
CallbackCompletionGuard<Result>::CallbackCompletionGuard(
const CancelRemainingWorkInLockFn& cancelRemainingWorkInLock,
const OnCompletionFn& onCompletion)
: _cancelRemainingWorkInLock(cancelRemainingWorkInLock), _onCompletion(onCompletion) {}
template <typename Result>
CallbackCompletionGuard<Result>::~CallbackCompletionGuard() {
invariant(_result);
// _onCompletion() must be called outside the caller's lock to avoid a deadlock.
// If '_onCompletion' throws an exception, the exception will be logged (by the terminate hook)
// and the program will abort.
_onCompletion(*_result);
}
template <typename Result>
void CallbackCompletionGuard<Result>::setResultAndCancelRemainingWork_inlock(
const stdx::lock_guard<stdx::mutex>& lock, const Result& result) {
_setResultAndCancelRemainingWork_inlock(result);
}
template <typename Result>
void CallbackCompletionGuard<Result>::setResultAndCancelRemainingWork_inlock(
const stdx::unique_lock<stdx::mutex>& lock, const Result& result) {
invariant(lock.owns_lock());
_setResultAndCancelRemainingWork_inlock(result);
}
template <typename Result>
void CallbackCompletionGuard<Result>::_setResultAndCancelRemainingWork_inlock(
const Result& result) {
if (_result) {
return;
}
_result = result;
// This is called at most once.
_cancelRemainingWorkInLock();
}
} // namespace repl
} // namespace mongo
|
