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
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
|
/* Copyright (c) 2018, 2020, MariaDB Corporation.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; version 2 of the License.
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 General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA */
/*
Implementation of BACKUP STAGE, an interface for external backup tools.
TODO:
- At backup_start() we call ha_prepare_for_backup() for all active
storage engines. If someone tries to load a new storage engine
that requires prepare_for_backup() for it to work, that storage
engines has to be blocked from loading until backup finishes.
As we currently don't have any loadable storage engine that
requires this and we have not implemented that part.
This can easily be done by adding a
PLUGIN_CANT_BE_LOADED_WHILE_BACKUP_IS_RUNNING flag to
maria_declare_plugin and check this before calling
plugin_initialize()
*/
#include "mariadb.h"
#include "sql_class.h"
#include "sql_base.h" // flush_tables
#include "sql_insert.h" // kill_delayed_threads
#include "sql_handler.h" // mysql_ha_cleanup_no_free
#include <my_sys.h>
#include "wsrep_mysqld.h"
static const char *stage_names[]=
{"START", "FLUSH", "BLOCK_DDL", "BLOCK_COMMIT", "END", 0};
TYPELIB backup_stage_names=
{ array_elements(stage_names)-1, "", stage_names, 0 };
static MDL_ticket *backup_flush_ticket;
static bool backup_start(THD *thd);
static bool backup_flush(THD *thd);
static bool backup_block_ddl(THD *thd);
static bool backup_block_commit(THD *thd);
/**
Run next stage of backup
*/
void backup_init()
{
backup_flush_ticket= 0;
}
bool run_backup_stage(THD *thd, backup_stages stage)
{
backup_stages next_stage;
DBUG_ENTER("run_backup_stage");
if (thd->current_backup_stage == BACKUP_FINISHED)
{
if (stage != BACKUP_START)
{
my_error(ER_BACKUP_NOT_RUNNING, MYF(0));
DBUG_RETURN(1);
}
next_stage= BACKUP_START;
}
else
{
if ((uint) thd->current_backup_stage >= (uint) stage)
{
my_error(ER_BACKUP_WRONG_STAGE, MYF(0), stage_names[stage],
stage_names[thd->current_backup_stage]);
DBUG_RETURN(1);
}
if (stage == BACKUP_END)
{
/*
If end is given, jump directly to stage end. This is to allow one
to abort backup quickly.
*/
next_stage= stage;
}
else
{
/* Go trough all not used stages until we reach 'stage' */
next_stage= (backup_stages) ((uint) thd->current_backup_stage + 1);
}
}
do
{
bool res= false;
backup_stages previous_stage= thd->current_backup_stage;
thd->current_backup_stage= next_stage;
switch (next_stage) {
case BACKUP_START:
if (!(res= backup_start(thd)))
break;
/* Reset backup stage to start for next backup try */
previous_stage= BACKUP_FINISHED;
break;
case BACKUP_FLUSH:
res= backup_flush(thd);
break;
case BACKUP_WAIT_FOR_FLUSH:
res= backup_block_ddl(thd);
break;
case BACKUP_LOCK_COMMIT:
res= backup_block_commit(thd);
break;
case BACKUP_END:
res= backup_end(thd);
break;
case BACKUP_FINISHED:
DBUG_ASSERT(0);
}
if (res)
{
thd->current_backup_stage= previous_stage;
my_error(ER_BACKUP_STAGE_FAILED, MYF(0), stage_names[(uint) stage]);
DBUG_RETURN(1);
}
next_stage= (backup_stages) ((uint) next_stage + 1);
} while ((uint) next_stage <= (uint) stage);
DBUG_RETURN(0);
}
/**
Start the backup
- Wait for previous backup to stop running
- Start service to log changed tables (TODO)
- Block purge of redo files (Required at least for Aria)
- An handler can optionally do a checkpoint of all tables,
to speed up the recovery stage of the backup.
*/
static bool backup_start(THD *thd)
{
MDL_request mdl_request;
DBUG_ENTER("backup_start");
thd->current_backup_stage= BACKUP_FINISHED; // For next test
if (thd->has_read_only_protection())
DBUG_RETURN(1);
thd->current_backup_stage= BACKUP_START;
if (thd->locked_tables_mode)
{
my_error(ER_LOCK_OR_ACTIVE_TRANSACTION, MYF(0));
DBUG_RETURN(1);
}
mdl_request.init(MDL_key::BACKUP, "", "", MDL_BACKUP_START, MDL_EXPLICIT);
if (thd->mdl_context.acquire_lock(&mdl_request,
thd->variables.lock_wait_timeout))
DBUG_RETURN(1);
backup_flush_ticket= mdl_request.ticket;
ha_prepare_for_backup();
DBUG_RETURN(0);
}
/**
backup_flush()
- FLUSH all changes for not active non transactional tables, except
for statistics and log tables. Close the tables, to ensure they
are marked as closed after backup.
- BLOCK all NEW write locks for all non transactional tables
(except statistics and log tables). Already granted locks are
not affected (Running statements with non transaction tables will
continue running).
- The following DDL's doesn't have to be blocked as they can't set
the table in a non consistent state:
CREATE, RENAME, DROP
*/
static bool backup_flush(THD *thd)
{
DBUG_ENTER("backup_flush");
/*
Lock all non transactional normal tables to be used in new DML's
*/
if (thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
MDL_BACKUP_FLUSH,
thd->variables.lock_wait_timeout))
DBUG_RETURN(1);
/*
Free unused tables and table shares so that mariabackup knows what
is safe to copy
*/
tc_purge(false);
tdc_purge(true);
DBUG_RETURN(0);
}
/**
backup_block_ddl()
- Kill all insert delay handlers, to ensure that all non transactional
tables are closed (can be improved in the future).
- Close handlers as other threads may wait for these, which can cause deadlocks.
- Wait for all statements using write locked non-transactional tables to end.
- Mark all not used active non transactional tables (except
statistics and log tables) to be closed with
handler->extra(HA_EXTRA_FLUSH)
- Block TRUNCATE TABLE, CREATE TABLE, DROP TABLE and RENAME
TABLE. Block also start of a new ALTER TABLE and the final rename
phase of ALTER TABLE. Running ALTER TABLES are not blocked. Both normal
and inline ALTER TABLE'S should be blocked when copying is completed but
before final renaming of the tables / new table is activated.
This will probably require a callback from the InnoDB code.
*/
static bool backup_block_ddl(THD *thd)
{
DBUG_ENTER("backup_block_ddl");
kill_delayed_threads();
mysql_ha_cleanup_no_free(thd);
/* Wait until all non trans statements has ended */
if (thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
MDL_BACKUP_WAIT_FLUSH,
thd->variables.lock_wait_timeout))
DBUG_RETURN(1);
/*
Remove not used tables from the table share. Flush all changes to
non transaction tables and mark those that are not in use in write
operations as closed. From backup purposes it's not critical if
flush_tables() returns an error. It's ok to continue with next
backup stage even if we got an error.
*/
(void) flush_tables(thd, FLUSH_NON_TRANS_TABLES);
thd->clear_error();
#ifdef WITH_WSREP
/*
We desync the node for BACKUP STAGE because applier threads
bypass backup MDL locks (see MDL_lock::can_grant_lock)
*/
if (WSREP_NNULL(thd))
{
Wsrep_server_state &server_state= Wsrep_server_state::instance();
if (server_state.desync_and_pause().is_undefined()) {
DBUG_RETURN(1);
}
thd->wsrep_desynced_backup_stage= true;
}
#endif /* WITH_WSREP */
/*
block new DDL's, in addition to all previous blocks
We didn't do this lock above, as we wanted DDL's to be executed while
we wait for non transactional tables (which may take a while).
*/
if (thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
MDL_BACKUP_WAIT_DDL,
thd->variables.lock_wait_timeout))
{
/*
Could be a timeout. Downgrade lock to what is was before this function
was called so that this function can be called again
*/
backup_flush_ticket->downgrade_lock(MDL_BACKUP_FLUSH);
DBUG_RETURN(1);
}
DBUG_RETURN(0);
}
/**
backup_block_commit()
Block commits, writes to log and statistics tables and binary log
*/
static bool backup_block_commit(THD *thd)
{
DBUG_ENTER("backup_block_commit");
if (thd->mdl_context.upgrade_shared_lock(backup_flush_ticket,
MDL_BACKUP_WAIT_COMMIT,
thd->variables.lock_wait_timeout))
DBUG_RETURN(1);
/* We can ignore errors from flush_tables () */
(void) flush_tables(thd, FLUSH_SYS_TABLES);
if (mysql_bin_log.is_open())
{
mysql_mutex_lock(mysql_bin_log.get_log_lock());
mysql_file_sync(mysql_bin_log.get_log_file()->file,
MYF(MY_WME|MY_SYNC_FILESIZE));
mysql_mutex_unlock(mysql_bin_log.get_log_lock());
}
thd->clear_error();
DBUG_RETURN(0);
}
/**
backup_end()
Safe to run, even if backup has not been run by this thread.
This is for example the case when a THD ends.
*/
bool backup_end(THD *thd)
{
DBUG_ENTER("backup_end");
if (thd->current_backup_stage != BACKUP_FINISHED)
{
ha_end_backup();
thd->current_backup_stage= BACKUP_FINISHED;
thd->mdl_context.release_lock(backup_flush_ticket);
#ifdef WITH_WSREP
if (WSREP_NNULL(thd) && thd->wsrep_desynced_backup_stage)
{
Wsrep_server_state &server_state= Wsrep_server_state::instance();
server_state.resume_and_resync();
thd->wsrep_desynced_backup_stage= false;
}
#endif /* WITH_WSREP */
}
DBUG_RETURN(0);
}
/**
backup_set_alter_copy_lock()
@param thd
@param table From table that is part of ALTER TABLE. This is only used
for the assert to ensure we use this function correctly.
Downgrades the MDL_BACKUP_DDL lock to MDL_BACKUP_ALTER_COPY to allow
copy of altered table to proceed under MDL_BACKUP_WAIT_DDL
Note that in some case when using non transactional tables,
the lock may be of type MDL_BACKUP_DML.
*/
void backup_set_alter_copy_lock(THD *thd, TABLE *table)
{
MDL_ticket *ticket= thd->mdl_backup_ticket;
/* Ticket maybe NULL in case of LOCK TABLES or for temporary tables*/
DBUG_ASSERT(ticket || thd->locked_tables_mode ||
table->s->tmp_table != NO_TMP_TABLE);
if (ticket)
ticket->downgrade_lock(MDL_BACKUP_ALTER_COPY);
}
/**
backup_reset_alter_copy_lock
Upgrade the lock of the original ALTER table MDL_BACKUP_DDL
Can fail if MDL lock was killed
*/
bool backup_reset_alter_copy_lock(THD *thd)
{
bool res= 0;
MDL_ticket *ticket= thd->mdl_backup_ticket;
/* Ticket maybe NULL in case of LOCK TABLES or for temporary tables*/
if (ticket)
res= thd->mdl_context.upgrade_shared_lock(ticket, MDL_BACKUP_DDL,
thd->variables.lock_wait_timeout);
return res;
}
/*****************************************************************************
Backup locks
These functions are used by maria_backup to ensure that there are no active
ddl's on the object the backup is going to copy
*****************************************************************************/
bool backup_lock(THD *thd, TABLE_LIST *table)
{
/* We should leave the previous table unlocked in case of errors */
backup_unlock(thd);
if (thd->locked_tables_mode)
{
my_error(ER_LOCK_OR_ACTIVE_TRANSACTION, MYF(0));
return 1;
}
table->mdl_request.duration= MDL_EXPLICIT;
if (thd->mdl_context.acquire_lock(&table->mdl_request,
thd->variables.lock_wait_timeout))
return 1;
thd->mdl_backup_lock= table->mdl_request.ticket;
return 0;
}
/* Release old backup lock if it exists */
void backup_unlock(THD *thd)
{
if (thd->mdl_backup_lock)
thd->mdl_context.release_lock(thd->mdl_backup_lock);
thd->mdl_backup_lock= 0;
}
|