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
|
/**
* 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/bson/bsonobjbuilder.h"
#include "mongo/platform/atomic_word.h"
#include "mongo/platform/mutex.h"
#include "mongo/stdx/condition_variable.h"
namespace mongo {
class OperationContext;
class ServiceContext;
/**
* This class is fundamentally a semaphore, but allows a caller to increment by X in constant time.
*
* Its expected usage maybe differs from a classic resource management protocol. Typically a client
* would acquire a ticket when it begins an operation and release the ticket to the pool when the
* operation is completed.
*
* In the context of flow control, clients take a ticket and do not return them to the pool. There
* is an external service that calculates the maximum number of tickets that should be allotted for
* the next time period (one second). The consumers will call `getTicket` and the producer will call
* `refreshTo`.
*/
class FlowControlTicketholder {
public:
/**
* A structure to accommodate curop reporting.
*/
struct CurOp {
bool waiting = false;
long long ticketsAcquired = 0;
long long acquireWaitCount = 0;
long long timeAcquiringMicros = 0;
/**
* Create a sub-object "flowControlStats" on the input builder and write in the structure's
* fields.
*/
void writeToBuilder(BSONObjBuilder& infoBuilder);
};
FlowControlTicketholder(int startTickets) : _tickets(startTickets), _inShutdown(false) {
_totalTimeAcquiringMicros.store(0);
}
static FlowControlTicketholder* get(ServiceContext* service);
static FlowControlTicketholder* get(ServiceContext& service);
static FlowControlTicketholder* get(OperationContext* opCtx);
static void set(ServiceContext* service, std::unique_ptr<FlowControlTicketholder> flowControl);
void refreshTo(int numTickets);
void getTicket(OperationContext* opCtx, FlowControlTicketholder::CurOp* stats);
std::int64_t totalTimeAcquiringMicros() const {
return _totalTimeAcquiringMicros.load();
}
void setInShutdown();
private:
// Use an int64_t as this is serialized to bson which does not support unsigned 64-bit numbers.
AtomicWord<std::int64_t> _totalTimeAcquiringMicros;
Mutex _mutex = MONGO_MAKE_LATCH("FlowControlTicketHolder::_mutex");
stdx::condition_variable _cv;
int _tickets;
bool _inShutdown; // used to synchronize shutdown of the ticket refresher job
};
} // namespace mongo
|
