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
160
161
162
|
/**
* Copyright (C) 2015 MongoDB Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* 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
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* 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 GNU Affero General 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.
*/
#include <memory>
#include <boost/optional.hpp>
#include <utility>
#include <vector>
#include "mongo/executor/task_executor.h"
#include "mongo/stdx/condition_variable.h"
#include "mongo/stdx/future.h"
#include "mongo/stdx/mutex.h"
#include "mongo/util/concurrency/thread_pool_interface.h"
namespace mongo {
namespace executor {
/**
* A mock class mimicking TaskExecutor::CallbackState, does nothing.
*/
class MockCallbackState final : public TaskExecutor::CallbackState {
public:
MockCallbackState() = default;
void cancel() override {}
void waitForCompletion() override {}
bool isCanceled() const override {
return false;
}
};
TaskExecutor::CallbackHandle makeCallbackHandle() {
return TaskExecutor::CallbackHandle(std::make_shared<MockCallbackState>());
}
/**
* Simple future-like utility for waiting for the result of startCommand.
*/
template <typename T>
class Deferred {
public:
template <typename... Args>
void emplace(Args&&... args) {
_emplace(_state.get(), std::forward<Args>(args)...);
}
T& get() {
return _get(_state.get());
}
bool hasCompleted() {
stdx::unique_lock<stdx::mutex> lk(_state->mtx);
return _state->thing.is_initialized();
}
template <typename Continuation>
auto then(ThreadPoolInterface* pool, Continuation&& continuation)
-> Deferred<decltype(continuation(std::declval<Deferred<T>>().get()))> {
// XXX: The ugliness of the above type signature is because you can't refer to 'this' in
// a template parameter, at least on g++-4.8.2.
auto state = _state;
Deferred<decltype(continuation(get()))> thenDeferred;
pool->schedule([this, thenDeferred, continuation, state]() mutable {
thenDeferred.emplace(continuation(_get(state.get())));
});
return thenDeferred;
}
private:
struct State {
stdx::mutex mtx;
stdx::condition_variable cv;
boost::optional<T> thing;
};
template <typename... Args>
void _emplace(State* state, Args&&... args) {
stdx::lock_guard<stdx::mutex> lk(_state->mtx);
invariant(!state->thing.is_initialized());
state->thing.emplace(std::forward<T>(args)...);
state->cv.notify_one();
}
T& _get(State* state) {
stdx::unique_lock<stdx::mutex> lk(state->mtx);
state->cv.wait(lk, [state] { return state->thing.is_initialized(); });
return *state->thing;
}
private:
std::shared_ptr<State> _state = std::make_shared<State>();
};
namespace helpers {
template <typename T>
static Deferred<std::vector<T>> collect(std::vector<Deferred<T>>& ds, ThreadPoolInterface* pool) {
Deferred<std::vector<T>> out;
struct CollectState {
// hack to avoid requiring U to be default constructible.
std::vector<boost::optional<T>> mem{};
std::size_t numFinished = 0;
std::size_t goal = 0;
stdx::mutex mtx;
};
auto collectState = std::make_shared<CollectState>();
collectState->goal = ds.size();
collectState->mem.resize(collectState->goal);
for (std::size_t i = 0; i < ds.size(); ++i) {
ds[i].then(pool,
[collectState, out, i](T res) mutable {
// The bool return is unused.
stdx::lock_guard<stdx::mutex> lk(collectState->mtx);
collectState->mem[i] = std::move(res);
// If we're done.
if (collectState->goal == ++collectState->numFinished) {
std::vector<T> outInitialized;
outInitialized.reserve(collectState->mem.size());
for (auto&& mem_entry : collectState->mem) {
outInitialized.emplace_back(std::move(*mem_entry));
}
out.emplace(outInitialized);
}
return true;
});
}
return out;
}
} // namespace helpers
} // namespace executor
} // namespace mongo
|
