Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * parsexlog.c
4 : * Functions for reading Write-Ahead-Log
5 : *
6 : * Portions Copyright (c) 1996-2019, PostgreSQL Global Development Group
7 : * Portions Copyright (c) 1994, Regents of the University of California
8 : *
9 : *-------------------------------------------------------------------------
10 : */
11 :
12 : #include "postgres_fe.h"
13 :
14 : #include <unistd.h>
15 :
16 : #include "pg_rewind.h"
17 : #include "filemap.h"
18 :
19 : #include "access/rmgr.h"
20 : #include "access/xlog_internal.h"
21 : #include "access/xlogreader.h"
22 : #include "catalog/pg_control.h"
23 : #include "catalog/storage_xlog.h"
24 : #include "commands/dbcommands_xlog.h"
25 :
26 :
27 : /*
28 : * RmgrNames is an array of resource manager names, to make error messages
29 : * a bit nicer.
30 : */
31 : #define PG_RMGR(symname,name,redo,desc,identify,startup,cleanup,mask) \
32 : name,
33 :
34 : static const char *RmgrNames[RM_MAX_ID + 1] = {
35 : #include "access/rmgrlist.h"
36 : };
37 :
38 : static void extractPageInfo(XLogReaderState *record);
39 :
40 : static int xlogreadfd = -1;
41 : static XLogSegNo xlogreadsegno = -1;
42 : static char xlogfpath[MAXPGPATH];
43 :
44 : typedef struct XLogPageReadPrivate
45 : {
46 : const char *datadir;
47 : int tliIndex;
48 : } XLogPageReadPrivate;
49 :
50 : static int SimpleXLogPageRead(XLogReaderState *xlogreader,
51 : XLogRecPtr targetPagePtr,
52 : int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
53 : TimeLineID *pageTLI);
54 :
55 : /*
56 : * Read WAL from the datadir/pg_wal, starting from 'startpoint' on timeline
57 : * index 'tliIndex' in target timeline history, until 'endpoint'. Make note of
58 : * the data blocks touched by the WAL records, and return them in a page map.
59 : */
60 : void
61 16 : extractPageMap(const char *datadir, XLogRecPtr startpoint, int tliIndex,
62 : XLogRecPtr endpoint)
63 : {
64 : XLogRecord *record;
65 : XLogReaderState *xlogreader;
66 : char *errormsg;
67 : XLogPageReadPrivate private;
68 :
69 16 : private.datadir = datadir;
70 16 : private.tliIndex = tliIndex;
71 16 : xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
72 : &private);
73 16 : if (xlogreader == NULL)
74 0 : pg_fatal("out of memory");
75 :
76 : do
77 : {
78 81832 : record = XLogReadRecord(xlogreader, startpoint, &errormsg);
79 :
80 81832 : if (record == NULL)
81 : {
82 : XLogRecPtr errptr;
83 :
84 0 : errptr = startpoint ? startpoint : xlogreader->EndRecPtr;
85 :
86 0 : if (errormsg)
87 0 : pg_fatal("could not read WAL record at %X/%X: %s",
88 : (uint32) (errptr >> 32), (uint32) (errptr),
89 : errormsg);
90 : else
91 0 : pg_fatal("could not read WAL record at %X/%X",
92 : (uint32) (errptr >> 32), (uint32) (errptr));
93 : }
94 :
95 81832 : extractPageInfo(xlogreader);
96 :
97 81832 : startpoint = InvalidXLogRecPtr; /* continue reading at next record */
98 :
99 81832 : } while (xlogreader->ReadRecPtr != endpoint);
100 :
101 16 : XLogReaderFree(xlogreader);
102 16 : if (xlogreadfd != -1)
103 : {
104 16 : close(xlogreadfd);
105 16 : xlogreadfd = -1;
106 : }
107 16 : }
108 :
109 : /*
110 : * Reads one WAL record. Returns the end position of the record, without
111 : * doing anything with the record itself.
112 : */
113 : XLogRecPtr
114 0 : readOneRecord(const char *datadir, XLogRecPtr ptr, int tliIndex)
115 : {
116 : XLogRecord *record;
117 : XLogReaderState *xlogreader;
118 : char *errormsg;
119 : XLogPageReadPrivate private;
120 : XLogRecPtr endptr;
121 :
122 0 : private.datadir = datadir;
123 0 : private.tliIndex = tliIndex;
124 0 : xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
125 : &private);
126 0 : if (xlogreader == NULL)
127 0 : pg_fatal("out of memory");
128 :
129 0 : record = XLogReadRecord(xlogreader, ptr, &errormsg);
130 0 : if (record == NULL)
131 : {
132 0 : if (errormsg)
133 0 : pg_fatal("could not read WAL record at %X/%X: %s",
134 : (uint32) (ptr >> 32), (uint32) (ptr), errormsg);
135 : else
136 0 : pg_fatal("could not read WAL record at %X/%X",
137 : (uint32) (ptr >> 32), (uint32) (ptr));
138 : }
139 0 : endptr = xlogreader->EndRecPtr;
140 :
141 0 : XLogReaderFree(xlogreader);
142 0 : if (xlogreadfd != -1)
143 : {
144 0 : close(xlogreadfd);
145 0 : xlogreadfd = -1;
146 : }
147 :
148 0 : return endptr;
149 : }
150 :
151 : /*
152 : * Find the previous checkpoint preceding given WAL location.
153 : */
154 : void
155 16 : findLastCheckpoint(const char *datadir, XLogRecPtr forkptr, int tliIndex,
156 : XLogRecPtr *lastchkptrec, TimeLineID *lastchkpttli,
157 : XLogRecPtr *lastchkptredo)
158 : {
159 : /* Walk backwards, starting from the given record */
160 : XLogRecord *record;
161 : XLogRecPtr searchptr;
162 : XLogReaderState *xlogreader;
163 : char *errormsg;
164 : XLogPageReadPrivate private;
165 :
166 : /*
167 : * The given fork pointer points to the end of the last common record,
168 : * which is not necessarily the beginning of the next record, if the
169 : * previous record happens to end at a page boundary. Skip over the page
170 : * header in that case to find the next record.
171 : */
172 16 : if (forkptr % XLOG_BLCKSZ == 0)
173 : {
174 4 : if (XLogSegmentOffset(forkptr, WalSegSz) == 0)
175 4 : forkptr += SizeOfXLogLongPHD;
176 : else
177 0 : forkptr += SizeOfXLogShortPHD;
178 : }
179 :
180 16 : private.datadir = datadir;
181 16 : private.tliIndex = tliIndex;
182 16 : xlogreader = XLogReaderAllocate(WalSegSz, &SimpleXLogPageRead,
183 : &private);
184 16 : if (xlogreader == NULL)
185 0 : pg_fatal("out of memory");
186 :
187 16 : searchptr = forkptr;
188 : for (;;)
189 208 : {
190 : uint8 info;
191 :
192 224 : record = XLogReadRecord(xlogreader, searchptr, &errormsg);
193 :
194 224 : if (record == NULL)
195 : {
196 0 : if (errormsg)
197 0 : pg_fatal("could not find previous WAL record at %X/%X: %s",
198 : (uint32) (searchptr >> 32), (uint32) (searchptr),
199 : errormsg);
200 : else
201 0 : pg_fatal("could not find previous WAL record at %X/%X",
202 : (uint32) (searchptr >> 32), (uint32) (searchptr));
203 : }
204 :
205 : /*
206 : * Check if it is a checkpoint record. This checkpoint record needs to
207 : * be the latest checkpoint before WAL forked and not the checkpoint
208 : * where the master has been stopped to be rewinded.
209 : */
210 224 : info = XLogRecGetInfo(xlogreader) & ~XLR_INFO_MASK;
211 432 : if (searchptr < forkptr &&
212 240 : XLogRecGetRmid(xlogreader) == RM_XLOG_ID &&
213 32 : (info == XLOG_CHECKPOINT_SHUTDOWN ||
214 : info == XLOG_CHECKPOINT_ONLINE))
215 : {
216 : CheckPoint checkPoint;
217 :
218 16 : memcpy(&checkPoint, XLogRecGetData(xlogreader), sizeof(CheckPoint));
219 16 : *lastchkptrec = searchptr;
220 16 : *lastchkpttli = checkPoint.ThisTimeLineID;
221 16 : *lastchkptredo = checkPoint.redo;
222 16 : break;
223 : }
224 :
225 : /* Walk backwards to previous record. */
226 208 : searchptr = record->xl_prev;
227 : }
228 :
229 16 : XLogReaderFree(xlogreader);
230 16 : if (xlogreadfd != -1)
231 : {
232 16 : close(xlogreadfd);
233 16 : xlogreadfd = -1;
234 : }
235 16 : }
236 :
237 : /* XLogReader callback function, to read a WAL page */
238 : static int
239 1340 : SimpleXLogPageRead(XLogReaderState *xlogreader, XLogRecPtr targetPagePtr,
240 : int reqLen, XLogRecPtr targetRecPtr, char *readBuf,
241 : TimeLineID *pageTLI)
242 : {
243 1340 : XLogPageReadPrivate *private = (XLogPageReadPrivate *) xlogreader->private_data;
244 : uint32 targetPageOff;
245 : XLogRecPtr targetSegEnd;
246 : XLogSegNo targetSegNo;
247 : int r;
248 :
249 1340 : XLByteToSeg(targetPagePtr, targetSegNo, WalSegSz);
250 1340 : XLogSegNoOffsetToRecPtr(targetSegNo + 1, 0, WalSegSz, targetSegEnd);
251 1340 : targetPageOff = XLogSegmentOffset(targetPagePtr, WalSegSz);
252 :
253 : /*
254 : * See if we need to switch to a new segment because the requested record
255 : * is not in the currently open one.
256 : */
257 2648 : if (xlogreadfd >= 0 &&
258 1308 : !XLByteInSeg(targetPagePtr, xlogreadsegno, WalSegSz))
259 : {
260 8 : close(xlogreadfd);
261 8 : xlogreadfd = -1;
262 : }
263 :
264 1340 : XLByteToSeg(targetPagePtr, xlogreadsegno, WalSegSz);
265 :
266 1340 : if (xlogreadfd < 0)
267 : {
268 : char xlogfname[MAXFNAMELEN];
269 :
270 : /*
271 : * Since incomplete segments are copied into next timelines, switch to
272 : * the timeline holding the required segment. Assuming this scan can
273 : * be done both forward and backward, consider also switching timeline
274 : * accordingly.
275 : */
276 80 : while (private->tliIndex < targetNentries - 1 &&
277 0 : targetHistory[private->tliIndex].end < targetSegEnd)
278 0 : private->tliIndex++;
279 80 : while (private->tliIndex > 0 &&
280 0 : targetHistory[private->tliIndex].begin >= targetSegEnd)
281 0 : private->tliIndex--;
282 :
283 40 : XLogFileName(xlogfname, targetHistory[private->tliIndex].tli,
284 : xlogreadsegno, WalSegSz);
285 :
286 40 : snprintf(xlogfpath, MAXPGPATH, "%s/" XLOGDIR "/%s", private->datadir, xlogfname);
287 :
288 40 : xlogreadfd = open(xlogfpath, O_RDONLY | PG_BINARY, 0);
289 :
290 40 : if (xlogreadfd < 0)
291 : {
292 0 : pg_log_error("could not open file \"%s\": %m", xlogfpath);
293 0 : return -1;
294 : }
295 : }
296 :
297 : /*
298 : * At this point, we have the right segment open.
299 : */
300 : Assert(xlogreadfd != -1);
301 :
302 : /* Read the requested page */
303 1340 : if (lseek(xlogreadfd, (off_t) targetPageOff, SEEK_SET) < 0)
304 : {
305 0 : pg_log_error("could not seek in file \"%s\": %m", xlogfpath);
306 0 : return -1;
307 : }
308 :
309 :
310 1340 : r = read(xlogreadfd, readBuf, XLOG_BLCKSZ);
311 1340 : if (r != XLOG_BLCKSZ)
312 : {
313 0 : if (r < 0)
314 0 : pg_log_error("could not read file \"%s\": %m", xlogfpath);
315 : else
316 0 : pg_log_error("could not read file \"%s\": read %d of %zu",
317 : xlogfpath, r, (Size) XLOG_BLCKSZ);
318 :
319 0 : return -1;
320 : }
321 :
322 : Assert(targetSegNo == xlogreadsegno);
323 :
324 1340 : *pageTLI = targetHistory[private->tliIndex].tli;
325 1340 : return XLOG_BLCKSZ;
326 : }
327 :
328 : /*
329 : * Extract information on which blocks the current record modifies.
330 : */
331 : static void
332 81832 : extractPageInfo(XLogReaderState *record)
333 : {
334 : int block_id;
335 81832 : RmgrId rmid = XLogRecGetRmid(record);
336 81832 : uint8 info = XLogRecGetInfo(record);
337 81832 : uint8 rminfo = info & ~XLR_INFO_MASK;
338 :
339 : /* Is this a special record type that I recognize? */
340 :
341 81832 : if (rmid == RM_DBASE_ID && rminfo == XLOG_DBASE_CREATE)
342 : {
343 : /*
344 : * New databases can be safely ignored. It won't be present in the
345 : * source system, so it will be deleted. There's one corner-case,
346 : * though: if a new, different, database is also created in the source
347 : * system, we'll see that the files already exist and not copy them.
348 : * That's OK, though; WAL replay of creating the new database, from
349 : * the source systems's WAL, will re-copy the new database,
350 : * overwriting the database created in the target system.
351 : */
352 : }
353 81828 : else if (rmid == RM_DBASE_ID && rminfo == XLOG_DBASE_DROP)
354 : {
355 : /*
356 : * An existing database was dropped. We'll see that the files don't
357 : * exist in the target data dir, and copy them in toto from the source
358 : * system. No need to do anything special here.
359 : */
360 : }
361 81828 : else if (rmid == RM_SMGR_ID && rminfo == XLOG_SMGR_CREATE)
362 : {
363 : /*
364 : * We can safely ignore these. The file will be removed from the
365 : * target, if it doesn't exist in source system. If a file with same
366 : * name is created in source system, too, there will be WAL records
367 : * for all the blocks in it.
368 : */
369 : }
370 81820 : else if (rmid == RM_SMGR_ID && rminfo == XLOG_SMGR_TRUNCATE)
371 : {
372 : /*
373 : * We can safely ignore these. When we compare the sizes later on,
374 : * we'll notice that they differ, and copy the missing tail from
375 : * source system.
376 : */
377 : }
378 81816 : else if (info & XLR_SPECIAL_REL_UPDATE)
379 : {
380 : /*
381 : * This record type modifies a relation file in some special way, but
382 : * we don't recognize the type. That's bad - we don't know how to
383 : * track that change.
384 : */
385 0 : pg_fatal("WAL record modifies a relation, but record type is not recognized: "
386 : "lsn: %X/%X, rmgr: %s, info: %02X",
387 : (uint32) (record->ReadRecPtr >> 32), (uint32) (record->ReadRecPtr),
388 : RmgrNames[rmid], info);
389 : }
390 :
391 163880 : for (block_id = 0; block_id <= record->max_block_id; block_id++)
392 : {
393 : RelFileNode rnode;
394 : ForkNumber forknum;
395 : BlockNumber blkno;
396 :
397 82048 : if (!XLogRecGetBlockTag(record, block_id, &rnode, &forknum, &blkno))
398 368 : continue;
399 :
400 : /* We only care about the main fork; others are copied in toto */
401 82048 : if (forknum != MAIN_FORKNUM)
402 368 : continue;
403 :
404 81680 : process_block_change(forknum, rnode, blkno);
405 : }
406 81832 : }
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