MySQL 8.0.30
Source Code Documentation
rpl_commit_stage_manager.h
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2
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21 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
22
23#ifndef RPL_COMMIT_STAGE_MANAGER
24#define RPL_COMMIT_STAGE_MANAGER
25
26#include <atomic>
27#include <utility>
28
29#include "my_dbug.h"
32#include "sql/sql_class.h"
33#include "thr_mutex.h"
34
35class THD;
36
37/**
38 Class for maintaining the commit stages for binary log group commit.
39 */
41 public:
44
45 public:
47
49
50 bool is_empty() const { return m_first == nullptr; }
51
52 /**
53 Append a linked list of threads to the queue.
54
55 @param[in] first Linked list of threads to be appended to queue
56
57 @retval true The queue was empty before this operation.
58 @retval false The queue was non-empty before this operation.
59 */
60 bool append(THD *first);
61
62 /**
63 Fetch the entire queue for a stage. It is a wrapper over
64 fetch_and_empty() and acquires queue lock before fetching
65 and emptying the queue threads.
66
67 @return Pointer to the first session of the queue.
68 */
70
71 /**
72 Fetch the entire queue for a stage. It is a wrapper over
73 fetch_and_empty(). The caller must acquire queue lock before
74 calling this function.
75
76 @return Pointer to the first session of the queue.
77 */
79
80 /**
81 Remove first member from the queue
82
83 @retval Returns std::pair<bool, THD *> object.
84 The first boolean value of pair if true determines queue
85 is not empty, and false determines queue is empty.
86 The second value returns the first removed member.
87 */
88 std::pair<bool, THD *> pop_front();
89
90 /**
91 Get number of elements in the queue.
92
93 @retval Returns number of element in the queue.
94 */
95 inline int32 get_size() { return m_size.load(); }
96
97 /**
98 Fetch the first thread of the queue.
99
100 @return first thread of the queue.
101 */
102 THD *get_leader() { return m_first; }
103
104 void lock() {
107 }
108
110
112
113 private:
114 /**
115 Fetch the entire queue for a stage.
116
117 @retval This will fetch the entire queue in one go.
118 */
120
121 /**
122 Pointer to the first thread in the queue, or nullptr if the queue is
123 empty.
124 */
126
127 /**
128 Pointer to the location holding the end of the queue.
129
130 This is either @c &first, or a pointer to the @c next_to_commit of
131 the last thread that is enqueued.
132 */
134
135 /** size of the queue */
136 std::atomic<int32> m_size;
137
138 /** Lock for protecting the queue. */
140
141 /*
142 This attribute did not have the desired effect, at least not according
143 to -fsanitize=undefined with gcc 5.2.1
144 */
145 }; // MY_ATTRIBUTE((aligned(CPU_LEVEL1_DCACHE_LINESIZE)));
146
147 private:
149
151
153
154 public:
155 /**
156 Fetch Commit_stage_manager class instance.
157
158 @return Reference to the Commit_stage_manager class instance.
159 */
161
162 /**
163 Constants for queues for different stages.
164 */
165 enum StageID {
171 };
172
173 /**
174 Initializes m_stage_cond_binlog, m_stage_cond_commit_order,
175 m_stage_cond_leader condition variables and m_lock_done mutex.
176
177 The binlog follower threads blocks on m_stage_cond_binlog condition
178 variable till signalled to wake up from leader thread. And similarly
179 commit order follower threads blocks on m_stage_cond_commit_order
180 condition variable till signalled to wake up from leader thread.
181
182 The first binlog thread supposed to be leader finds that commit order queue
183 is not empty then it blocks on m_stage_cond_leader till commit order leader
184 signals it to awake and become new leader.
185
186 m_lock_done mutex is shared by all three stages.
187
188 @param key_LOCK_flush_queue mutex instrumentation key
189 @param key_LOCK_sync_queue mutex instrumentation key
190 @param key_LOCK_commit_queue mutex instrumentation key
191 @param key_LOCK_done mutex instrumentation key
192 @param key_COND_done cond instrumentation key
193 @param key_COND_flush_queue cond instrumentation key
194 */
195 void init(PSI_mutex_key key_LOCK_flush_queue,
196 PSI_mutex_key key_LOCK_sync_queue,
197 PSI_mutex_key key_LOCK_commit_queue, PSI_mutex_key key_LOCK_done,
198 PSI_cond_key key_COND_done, PSI_cond_key key_COND_flush_queue);
199
200 /**
201 Deinitializes m_stage_cond_binlog, m_stage_cond_commit_order,
202 m_stage_cond_leader condition variables and m_lock_done mutex.
203 */
204 void deinit();
205
206 /**
207 Enroll a set of sessions for a stage.
208
209 This will queue the session thread for writing and flushing.
210
211 If the thread being queued is assigned as stage leader, it will
212 return immediately.
213
214 If wait_if_follower is true the thread is not the stage leader,
215 the thread will be wait for the queue to be processed by the
216 leader before it returns.
217 In DBUG-ON version the follower marks is preempt status as ready.
218
219 The session threads entering this function acquires mutexes, and few of
220 them are not released while exiting based on thread and stage type.
221 - A binlog leader (returning true when stage!=COMMIT_ORDER_FLUSH_STAGE) will
222 acquire the stage mutex in this function and not release it.
223 - A commit order leader of the flush stage (returning true when
224 stage==COMMIT_ORDER_FLUSH_STAGE) will acquire both the stage mutex and the
225 flush queue mutex in this function, and not release them.
226 - A follower (returning false) will release any mutexes it takes, before
227 returning from the function.
228
229 @param[in] stage Stage identifier for the queue to append to.
230 @param[in] first Queue to append.
231 @param[in] stage_mutex
232 Pointer to the currently held stage mutex, or nullptr if we're
233 not in a stage, that will be released when changing stage.
234 @param[in] enter_mutex
235 Pointer to the mutex that will be taken when changing stage.
236
237 @retval true Thread is stage leader.
238 @retval false Thread was not stage leader and processing has been done.
239 */
240 bool enroll_for(StageID stage, THD *first, mysql_mutex_t *stage_mutex,
241 mysql_mutex_t *enter_mutex);
242
243 /**
244 Remove first member from the queue for given stage
245
246 @retval Returns std::pair<bool, THD *> object.
247 The first boolean value of pair if true determines queue
248 is not empty, and false determines queue is empty.
249 The second value returns the first removed member.
250 */
251 std::pair<bool, THD *> pop_front(StageID stage) {
252 return m_queue[stage].pop_front();
253 }
254
255#ifndef NDEBUG
256 /**
257 The method ensures the follower's execution path can be preempted
258 by the leader's thread.
259 Preempt status of @c head follower is checked to engange the leader
260 into waiting when set.
261
262 @param head THD* of a follower thread
263 */
264 void clear_preempt_status(THD *head);
265#endif
266
267 /**
268 Fetch the entire queue and empty it. It acquires queue lock before fetching
269 and emptying the queue threads.
270
271 @param[in] stage Stage identifier for the queue to append to.
272
273 @return Pointer to the first session of the queue.
274 */
276
277 /**
278 Fetch the entire queue and empty it. The caller must acquire queue lock
279 before calling this function.
280
281 @param[in] stage Stage identifier for the queue to append to.
282
283 @return Pointer to the first session of the queue.
284 */
286
287 /**
288 Introduces a wait operation on the executing thread. The
289 waiting is done until the timeout elapses or count is
290 reached (whichever comes first).
291
292 If count == 0, then the session will wait until the timeout
293 elapses. If timeout == 0, then there is no waiting.
294
295 @param usec the number of microseconds to wait.
296 @param count wait for as many as count to join the queue the
297 session is waiting on
298 @param stage which stage queue size to compare count against.
299 */
300 void wait_count_or_timeout(ulong count, long usec, StageID stage);
301
302 /**
303 The function is called after follower thread are processed by leader,
304 to unblock follower threads.
305
306 @param queue the thread list which needs to ne unblocked
307 @param stage Stage identifier current thread belong to.
308 */
310
311 /**
312 This function gets called after transactions are flushed to the engine
313 i.e. after calling ha_flush_logs, to unblock commit order thread list
314 which are not needed to wait for other stages.
315
316 @param first the thread list which needs to ne unblocked
317 */
319
320 /**
321 Wrapper on Mutex_queue lock(), acquires lock on stage queue.
322
323 @param[in] stage Stage identifier for the queue to append to.
324 */
325 void lock_queue(StageID stage) { m_queue[stage].lock(); }
326
327 /**
328 Wrapper on Mutex_queue unlock(), releases lock on stage queue.
329
330 @param[in] stage Stage identifier for the queue to append to.
331 */
332 void unlock_queue(StageID stage) { m_queue[stage].unlock(); }
333
334 private:
335 /** check if Commit_stage_manager variables already initialized. */
337
338 /**
339 Queues for sessions.
340
341 We need four queues:
342 - Binlog flush queue: transactions that are going to be flushed to the
343 engine and written to the binary log.
344 - Commit order flush queue: transactions that are not going to write the
345 binlog at all, but participate in the beginning
346 of the group commit, up to and including the
347 engine flush.
348 - Sync queue: transactions that are going to be synced to disk
349 - Commit queue: transactions that are going to to be committed
350 (when binlog_order_commit=1).
351 */
353
354 /**
355 The binlog leader waits on this condition variable till it is indicated
356 to wake up. If binlog flush queue gets first thread in the queue but
357 by then commit order flush queue has already elected leader. The the
358 first thread of binlog queue waits on this condition variable and get
359 signalled to wake up from commit order flush queue leader later.
360 */
362
363 /**
364 Condition variable to indicate that the binlog threads can wake up
365 and continue.
366 */
368
369 /**
370 Condition variable to indicate that the flush to storage engine
371 is done and commit order threads can again wake up and continue.
372 */
374
375 /** Mutex used for the condition variable above */
377
378 /** Mutex used for the stage level locks */
380
381#ifndef NDEBUG
382 /** Save pointer to leader thread which is used later to awake leader */
384
385 /** Flag is set by Leader when it starts waiting for follower's all-clear */
387
388 /** Condition variable to indicate a follower started waiting for commit */
390#endif
391};
392
393#endif /*RPL_COMMIT_STAGE_MANAGER*/
Definition: rpl_commit_stage_manager.h:42
THD * fetch_and_empty_acquire_lock()
Fetch the entire queue for a stage.
Definition: rpl_commit_stage_manager.cc:336
THD * fetch_and_empty_skip_acquire_lock()
Fetch the entire queue for a stage.
Definition: rpl_commit_stage_manager.cc:343
std::atomic< int32 > m_size
size of the queue
Definition: rpl_commit_stage_manager.h:136
mysql_mutex_t * m_lock
Lock for protecting the queue.
Definition: rpl_commit_stage_manager.h:139
bool is_empty() const
Definition: rpl_commit_stage_manager.h:50
bool append(THD *first)
Append a linked list of threads to the queue.
Definition: rpl_commit_stage_manager.cc:36
void assert_owner()
Definition: rpl_commit_stage_manager.h:111
THD * get_leader()
Fetch the first thread of the queue.
Definition: rpl_commit_stage_manager.h:102
void init(mysql_mutex_t *lock)
Definition: rpl_commit_stage_manager.h:48
int32 get_size()
Get number of elements in the queue.
Definition: rpl_commit_stage_manager.h:95
void unlock()
Definition: rpl_commit_stage_manager.h:109
void lock()
Definition: rpl_commit_stage_manager.h:104
THD ** m_last
Pointer to the location holding the end of the queue.
Definition: rpl_commit_stage_manager.h:133
THD * fetch_and_empty()
Fetch the entire queue for a stage.
Definition: rpl_commit_stage_manager.cc:348
Mutex_queue()
Definition: rpl_commit_stage_manager.h:46
std::pair< bool, THD * > pop_front()
Remove first member from the queue.
Definition: rpl_commit_stage_manager.cc:70
THD * m_first
Pointer to the first thread in the queue, or nullptr if the queue is empty.
Definition: rpl_commit_stage_manager.h:125
Class for maintaining the commit stages for binary log group commit.
Definition: rpl_commit_stage_manager.h:40
const Commit_stage_manager & operator=(const Commit_stage_manager &)=delete
mysql_mutex_t m_lock_done
Mutex used for the condition variable above.
Definition: rpl_commit_stage_manager.h:376
std::pair< bool, THD * > pop_front(StageID stage)
Remove first member from the queue for given stage.
Definition: rpl_commit_stage_manager.h:251
mysql_cond_t m_stage_cond_leader
The binlog leader waits on this condition variable till it is indicated to wake up.
Definition: rpl_commit_stage_manager.h:361
void deinit()
Deinitializes m_stage_cond_binlog, m_stage_cond_commit_order, m_stage_cond_leader condition variables...
Definition: rpl_commit_stage_manager.cc:134
bool leader_await_preempt_status
Flag is set by Leader when it starts waiting for follower's all-clear.
Definition: rpl_commit_stage_manager.h:386
mysql_cond_t m_stage_cond_binlog
Condition variable to indicate that the binlog threads can wake up and continue.
Definition: rpl_commit_stage_manager.h:367
void clear_preempt_status(THD *head)
The method ensures the follower's execution path can be preempted by the leader's thread.
Definition: rpl_commit_stage_manager.cc:424
Mutex_queue m_queue[STAGE_COUNTER]
Queues for sessions.
Definition: rpl_commit_stage_manager.h:352
Commit_stage_manager(const Commit_stage_manager &)=delete
mysql_cond_t m_stage_cond_commit_order
Condition variable to indicate that the flush to storage engine is done and commit order threads can ...
Definition: rpl_commit_stage_manager.h:373
mysql_mutex_t m_queue_lock[STAGE_COUNTER - 1]
Mutex used for the stage level locks.
Definition: rpl_commit_stage_manager.h:379
StageID
Constants for queues for different stages.
Definition: rpl_commit_stage_manager.h:165
@ COMMIT_ORDER_FLUSH_STAGE
Definition: rpl_commit_stage_manager.h:169
@ COMMIT_STAGE
Definition: rpl_commit_stage_manager.h:168
@ BINLOG_FLUSH_STAGE
Definition: rpl_commit_stage_manager.h:166
@ SYNC_STAGE
Definition: rpl_commit_stage_manager.h:167
@ STAGE_COUNTER
Definition: rpl_commit_stage_manager.h:170
static Commit_stage_manager & get_instance()
Fetch Commit_stage_manager class instance.
Definition: rpl_commit_stage_manager.cc:437
THD * fetch_queue_acquire_lock(StageID stage)
Fetch the entire queue and empty it.
Definition: rpl_commit_stage_manager.cc:389
bool m_is_initialized
check if Commit_stage_manager variables already initialized.
Definition: rpl_commit_stage_manager.h:336
Commit_stage_manager()
Definition: rpl_commit_stage_manager.h:148
void wait_count_or_timeout(ulong count, long usec, StageID stage)
Introduces a wait operation on the executing thread.
Definition: rpl_commit_stage_manager.cc:366
void lock_queue(StageID stage)
Wrapper on Mutex_queue lock(), acquires lock on stage queue.
Definition: rpl_commit_stage_manager.h:325
THD * leader_thd
Save pointer to leader thread which is used later to awake leader.
Definition: rpl_commit_stage_manager.h:383
void process_final_stage_for_ordered_commit_group(THD *first)
This function gets called after transactions are flushed to the engine i.e.
Definition: rpl_commit_stage_manager.cc:399
THD * fetch_queue_skip_acquire_lock(StageID stage)
Fetch the entire queue and empty it.
Definition: rpl_commit_stage_manager.cc:394
mysql_cond_t m_cond_preempt
Condition variable to indicate a follower started waiting for commit.
Definition: rpl_commit_stage_manager.h:389
void signal_done(THD *queue, StageID stage=BINLOG_FLUSH_STAGE)
The function is called after follower thread are processed by leader, to unblock follower threads.
Definition: rpl_commit_stage_manager.cc:407
void init(PSI_mutex_key key_LOCK_flush_queue, PSI_mutex_key key_LOCK_sync_queue, PSI_mutex_key key_LOCK_commit_queue, PSI_mutex_key key_LOCK_done, PSI_cond_key key_COND_done, PSI_cond_key key_COND_flush_queue)
Initializes m_stage_cond_binlog, m_stage_cond_commit_order, m_stage_cond_leader condition variables a...
Definition: rpl_commit_stage_manager.cc:95
void unlock_queue(StageID stage)
Wrapper on Mutex_queue unlock(), releases lock on stage queue.
Definition: rpl_commit_stage_manager.h:332
bool enroll_for(StageID stage, THD *first, mysql_mutex_t *stage_mutex, mysql_mutex_t *enter_mutex)
Enroll a set of sessions for a stage.
Definition: rpl_commit_stage_manager.cc:146
For each client connection we create a separate thread with THD serving as a thread/connection descri...
Definition: sql_class.h:922
#define mysql_mutex_lock(M)
Definition: mysql_mutex.h:49
#define mysql_mutex_unlock(M)
Definition: mysql_mutex.h:56
Fido Client Authentication nullptr
Definition: fido_client_plugin.cc:221
unsigned int PSI_cond_key
Instrumented cond key.
Definition: psi_cond_bits.h:43
unsigned int PSI_mutex_key
Instrumented mutex key.
Definition: psi_mutex_bits.h:51
#define mysql_mutex_assert_not_owner(M)
Wrapper, to use safe_mutex_assert_not_owner with instrumented mutexes.
Definition: mysql_mutex.h:125
#define mysql_mutex_assert_owner(M)
Wrapper, to use safe_mutex_assert_owner with instrumented mutexes.
Definition: mysql_mutex.h:111
int32_t int32
Definition: my_inttypes.h:65
static int count
Definition: myisam_ftdump.cc:42
static QUEUE queue
Definition: myisampack.cc:206
Provides atomic access in shared-exclusive modes.
Definition: shared_spin_lock.h:78
Instrumentation helpers for conditions.
Instrumentation helpers for mutexes.
An instrumented cond structure.
Definition: mysql_cond_bits.h:49
An instrumented mutex structure.
Definition: mysql_mutex_bits.h:49
MySQL mutex implementation.