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
|
/**
* 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 "mongo/base/status_with.h"
#include "mongo/executor/task_executor.h"
#include "mongo/platform/mutex.h"
namespace mongo {
namespace repl {
/**
* The RollbackChecker maintains a sync source and its baseline rollback ID (rbid). It
* contains methods to check if a rollback occurred by checking if the rbid has changed since
* the baseline was set.
*
* To use the RollbackChecker:
* 1) Create a RollbackChecker by passing in an executor, and a sync source to use. If the
* sync source changes, make a new RollbackChecker.
* 2) Call reset(), either synchronously or asynchronously, so that the RollbackChecker retrieves
* the state it needs from the sync source to check for rollbacks.
* 3) Call checkForRollback(), passing in a 'nextAction' callback. This checks if there was a
* rollback at the sync source. If there is a rollback or another error, the 'nextAction'
* callback will be invoked. This error could be an UnrecoverableRollbackError, when there is a
* rollback.
* The only case where 'nextAction' is not called is when checkForRollback fails because the
* task executor is unable to schedule the remote replSetGetRBID command. In this case,
* checkForRollback() returns the error from executorTaskExecutor::scheduleRemoteCommand().
* Alternatively, call hasHadRollback() which synchronously checks for a rollback and returns
* true if any error occurs. Checking for a rollback does not reset the baseline rbid.
* 4) Repeat steps 2 and 3 as needed.
*
*/
class RollbackChecker {
RollbackChecker(const RollbackChecker&) = delete;
RollbackChecker& operator=(const RollbackChecker&) = delete;
public:
// Rollback checker result - true if rollback occurred; false if rollback IDs
// were the same; Otherwise, error status indicating why rollback check failed.
using Result = StatusWith<bool>;
using CallbackFn = std::function<void(const Result& result)>;
using RemoteCommandCallbackFn = executor::TaskExecutor::RemoteCommandCallbackFn;
using CallbackHandle = executor::TaskExecutor::CallbackHandle;
RollbackChecker(executor::TaskExecutor* executor, HostAndPort syncSource);
virtual ~RollbackChecker();
// Checks whether the the sync source has had a rollback since the last time reset was called,
// and then calls the nextAction with the rollback checker result. An error status
// will be passed to the callback if the RBID cannot be determined or if
// the callback was canceled.
StatusWith<CallbackHandle> checkForRollback(const CallbackFn& nextAction);
// Synchronously checks if there has been a rollback and returns a boolean specifying if one
// has occurred.
Result hasHadRollback();
// Resets the state used to decide if a rollback occurs, and then calls the nextAction with a
// status specifying what should occur next. The status will either be OK if there was no
// error or another status if the command failed. The nextAction should account for
// each of these cases.
StatusWith<CallbackHandle> reset(const CallbackFn& nextAction);
// Synchronously calls reset and returns the Status of the command.
Status reset_sync();
// Returns the current baseline rbid.
int getBaseRBID();
// ================== Test Support API ===================
// Returns the last rbid seen.
int getLastRBID_forTest();
private:
// Assumes a lock has been taken. Returns if a rollback has occurred by comparing the remoteRBID
// provided and the stored baseline rbid. Sets _lastRBID to the remoteRBID provided.
bool _checkForRollback_inlock(int remoteRBID);
// Schedules a remote command to get the rbid at the sync source and then calls the nextAction.
// If there is an error scheduling the call, it returns the error from
// TaskExecutor::scheduleRemoteCommand().
StatusWith<CallbackHandle> _scheduleGetRollbackId(const RemoteCommandCallbackFn& nextAction);
// Assumes a lock has been taken. Sets the current rbid used as the baseline for rollbacks.
void _setRBID_inlock(int rbid);
// Not owned by us.
executor::TaskExecutor* const _executor;
// Protects member data of this RollbackChecker.
mutable Mutex _mutex = MONGO_MAKE_LATCH("RollbackChecker::_mutex");
// The sync source to check for rollbacks against.
HostAndPort _syncSource;
// The baseline rbid of the sync source to use when deciding if a rollback should occur.
int _baseRBID;
// The last rbid that we saw.
int _lastRBID;
};
} // namespace repl
} // namespace mongo
|
