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Commit04834e7

Browse files
author
Michael Paquier
committed
Page-level backup using block tracking in WAL records
This commit improves the performance of page-level, or differentialbackup, by not having to scan anymore all the pages of a relation file,something that can be very long on large data sets, but by scanning thelist of blocks changed by WAL records since the last full or differentialbackup.As a restriction and to avoid potential data corruption should hint-bitupdates occur on a page, backups can only be taken from a server that haswal_log_hints or data checksums enabled.Base patch by Yury Zhuravlev, heavily modified by me.
1 parent47d0b60 commit04834e7

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12 files changed

+578
-119
lines changed

12 files changed

+578
-119
lines changed

‎.gitignore

Lines changed: 5 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -25,3 +25,8 @@
2525
/regression.diffs
2626
/regression.out
2727
/results
28+
29+
# Extra files
30+
/datapagemap.c
31+
/datapagemap.h
32+
/xlogreader.c

‎Makefile

Lines changed: 32 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -14,11 +14,16 @@ OBJS = backup.o \
1414
util.o\
1515
validate.o\
1616
xlog.o\
17+
datapagemap.o\
18+
parsexlog.o\
19+
xlogreader.o\
1720
pgut/pgut.o\
1821
pgut/pgut-port.o
1922

2023
DOCS = doc/pg_arman.txt
2124

25+
EXTRA_CLEAN = datapagemap.c datapagemap.h xlogreader.c
26+
2227
# asciidoc and xmlto are present, so install the html documentation and man
2328
# pages as well. html is part of the vanilla documentation. Man pages need a
2429
# special handling at installation.
@@ -35,6 +40,27 @@ PG_LIBS = $(libpq_pgport)
3540

3641
REGRESS = init option show delete backup restore
3742

43+
all: checksrcdir docs datapagemap.h pg_arman
44+
45+
# This rule's only purpose is to give the user instructions on how to pass
46+
# the path to PostgreSQL source tree to the makefile.
47+
.PHONY: checksrcdir
48+
checksrcdir:
49+
ifndeftop_srcdir
50+
@echo "You must have PostgreSQL source tree available to compile."
51+
@echo "Pass the path to the PostgreSQL source tree to make, in the top_srcdir"
52+
@echo "variable: \"make top_srcdir=<path to PostgreSQL source tree>\""
53+
@exit 1
54+
endif
55+
56+
# Those files are symlinked from the PostgreSQL sources.
57+
xlogreader.c:% :$(top_srcdir)/src/backend/access/transam/%
58+
rm -f$@&&$(LN_S)$<.
59+
datapagemap.c:% :$(top_srcdir)/src/bin/pg_rewind/%
60+
rm -f$@&&$(LN_S)$<.
61+
datapagemap.h:% :$(top_srcdir)/src/bin/pg_rewind/%
62+
rm -f&&$(LN_S)$<.
63+
3864
PG_CONFIG = pg_config
3965
PGXS :=$(shell$(PG_CONFIG) --pgxs)
4066
include$(PGXS)
@@ -43,7 +69,6 @@ include $(PGXS)
4369
# Compile documentation as well is ASCIIDOC and XMLTO are defined
4470
ifneq ($(ASCIIDOC),)
4571
ifneq ($(XMLTO),)
46-
all: docs
4772
docs:
4873
$(MAKE) -C doc/
4974

@@ -53,7 +78,13 @@ install: install-man
5378
install-man:
5479
$(MKDIR_P)'$(DESTDIR)$(mandir)/man1/'
5580
$(INSTALL_DATA)$(man_DOCS)'$(DESTDIR)$(mandir)/man1/'
81+
else
82+
docs:
83+
@echo"No docs to build"
5684
endif# XMLTO
85+
else
86+
docs:
87+
@echo"No docs to build"
5788
endif# ASCIIDOC
5889

5990
# Clean up documentation as well

‎backup.c

Lines changed: 120 additions & 18 deletions
Original file line numberDiff line numberDiff line change
@@ -28,6 +28,9 @@ static int server_version = 0;
2828

2929
staticboolin_backup= false;/* TODO: more robust logic */
3030

31+
/* list of files contained in backup */
32+
parray*backup_files_list;
33+
3134
/*
3235
* Backup routines
3336
*/
@@ -48,6 +51,7 @@ static void create_file_list(parray *files,
4851
constchar*subdir,
4952
constchar*prefix,
5053
boolis_append);
54+
staticvoidwait_for_archive(pgBackup*backup,constchar*sql);
5155

5256
/*
5357
* Take a backup of database and return the list of files backed up.
@@ -56,7 +60,6 @@ static parray *
5660
do_backup_database(parray*backup_list,pgBackupOptionbkupopt)
5761
{
5862
inti;
59-
parray*files;/* backup file list from non-snapshot */
6063
parray*prev_files=NULL;/* file list of previous database backup */
6164
FILE*fp;
6265
charpath[MAXPGPATH];
@@ -68,6 +71,7 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
6871

6972
/* repack the options */
7073
boolsmooth_checkpoint=bkupopt.smooth_checkpoint;
74+
pgBackup*prev_backup=NULL;
7175

7276
/* Block backup operations on a standby */
7377
if (pg_is_standby())
@@ -78,6 +82,9 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
7882
/* Initialize size summary */
7983
current.data_bytes=0;
8084

85+
/* do some checks on the node */
86+
sanityChecks();
87+
8188
/*
8289
* Obtain current timeline by scanning control file, theh LSN
8390
* obtained at output of pg_start_backup or pg_stop_backup does
@@ -123,8 +130,8 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
123130
* List directories and symbolic links with the physical path to make
124131
* mkdirs.sh, then sort them in order of path. Omit $PGDATA.
125132
*/
126-
files=parray_new();
127-
dir_list_file(files,pgdata,NULL, false, false);
133+
backup_files_list=parray_new();
134+
dir_list_file(backup_files_list,pgdata,NULL, false, false);
128135

129136
if (!check)
130137
{
@@ -133,26 +140,24 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
133140
if (fp==NULL)
134141
elog(ERROR_SYSTEM,"can't open make directory script \"%s\": %s",
135142
path,strerror(errno));
136-
dir_print_mkdirs_sh(fp,files,pgdata);
143+
dir_print_mkdirs_sh(fp,backup_files_list,pgdata);
137144
fclose(fp);
138145
if (chmod(path,DIR_PERMISSION)==-1)
139146
elog(ERROR_SYSTEM,"can't change mode of \"%s\": %s",path,
140147
strerror(errno));
141148
}
142149

143150
/* clear directory list */
144-
parray_walk(files,pgFileFree);
145-
parray_free(files);
146-
files=NULL;
151+
parray_walk(backup_files_list,pgFileFree);
152+
parray_free(backup_files_list);
153+
backup_files_list=NULL;
147154

148155
/*
149156
* To take differential backup, the file list of the last completed database
150157
* backup is needed.
151158
*/
152159
if (current.backup_mode==BACKUP_MODE_DIFF_PAGE)
153160
{
154-
pgBackup*prev_backup;
155-
156161
/* find last completed database backup */
157162
prev_backup=catalog_get_last_data_backup(backup_list,current.tli);
158163
pgBackupGetPath(prev_backup,prev_file_txt,lengthof(prev_file_txt),
@@ -167,26 +172,55 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
167172
(uint32) (*lsn >>32), (uint32)*lsn);
168173
}
169174

170-
/* initialize backup listfrom non-snapshot*/
171-
files=parray_new();
175+
/* initialize backup list */
176+
backup_files_list=parray_new();
172177

173178
/* list files with the logical path. omit $PGDATA */
174-
add_files(files,pgdata, false, true);
179+
add_files(backup_files_list,pgdata, false, true);
175180

176181
/* backup files */
177182
pgBackupGetPath(&current,path,lengthof(path),DATABASE_DIR);
178-
backup_files(pgdata,path,files,prev_files,lsn,NULL);
183+
184+
/*
185+
* Build page mapping in differential mode. When using this mode, the
186+
* list of blocks to be taken is known by scanning the WAL segments
187+
* present in archives up to the point where start backup has begun.
188+
* However, normally this segment is not yet available in the archives,
189+
* leading to failures when building the page map. Hence before doing
190+
* anything and in order to ensure that all the segments needed for the
191+
* scan are here, for a switch of the last segment with pg_switch_xlog.
192+
*/
193+
if (current.backup_mode==BACKUP_MODE_DIFF_PAGE)
194+
{
195+
/* Enforce archiving of last segment and wait for it to be here */
196+
wait_for_archive(&current,"SELECT * FROM pg_switch_xlog()");
197+
198+
/* Now build the page map */
199+
parray_qsort(backup_files_list,pgFileComparePathDesc);
200+
elog(LOG,"extractPageMap");
201+
elog(LOG,"current_tli:%X",current.tli);
202+
elog(LOG,"prev_backup->start_lsn: %X/%X",
203+
(uint32) (prev_backup->start_lsn >>32),
204+
(uint32) (prev_backup->start_lsn));
205+
elog(LOG,"current.start_lsn: %X/%X",
206+
(uint32) (current.start_lsn >>32),
207+
(uint32) (current.start_lsn));
208+
extractPageMap(arclog_path,prev_backup->start_lsn,current.tli,
209+
current.start_lsn);
210+
}
211+
212+
backup_files(pgdata,path,backup_files_list,prev_files,lsn,NULL);
179213

180214
/* notify end of backup */
181215
pg_stop_backup(&current);
182216

183217
/* create file list */
184-
create_file_list(files,pgdata,DATABASE_FILE_LIST,NULL, false);
218+
create_file_list(backup_files_list,pgdata,DATABASE_FILE_LIST,NULL, false);
185219

186220
/* print summary of size of backup mode files */
187-
for (i=0;i<parray_num(files);i++)
221+
for (i=0;i<parray_num(backup_files_list);i++)
188222
{
189-
pgFile*file= (pgFile*)parray_get(files,i);
223+
pgFile*file= (pgFile*)parray_get(backup_files_list,i);
190224
if (!S_ISREG(file->mode))
191225
continue;
192226
/*
@@ -204,7 +238,7 @@ do_backup_database(parray *backup_list, pgBackupOption bkupopt)
204238
current.data_bytes);
205239
elog(LOG,"========================================");
206240

207-
returnfiles;
241+
returnbackup_files_list;
208242
}
209243

210244

@@ -654,7 +688,6 @@ backup_files(const char *from_root,
654688
}
655689
else
656690
{
657-
elog(LOG,"\n");
658691
elog(ERROR_SYSTEM,
659692
"can't stat backup mode. \"%s\": %s",
660693
file->path,strerror(errno));
@@ -825,3 +858,72 @@ create_file_list(parray *files,
825858
fclose(fp);
826859
}
827860
}
861+
862+
/*
863+
* A helper function to create the path of a relation file and segment.
864+
*
865+
* The returned path is palloc'd
866+
*/
867+
staticchar*
868+
datasegpath(RelFileNodernode,ForkNumberforknum,BlockNumbersegno)
869+
{
870+
char*path;
871+
char*segpath;
872+
873+
path=relpathperm(rnode,forknum);
874+
if (segno>0)
875+
{
876+
segpath=psprintf("%s.%u",path,segno);
877+
pfree(path);
878+
returnsegpath;
879+
}
880+
else
881+
returnpath;
882+
}
883+
884+
/*
885+
* This routine gets called while reading WAL segments from the WAL archive,
886+
* for every block that have changed in the target system. It makes note of
887+
* all the changed blocks in the pagemap of the file and adds them in the
888+
* things to track for the backup.
889+
*/
890+
void
891+
process_block_change(ForkNumberforknum,RelFileNodernode,BlockNumberblkno)
892+
{
893+
char*path;
894+
char*rel_path;
895+
BlockNumberblkno_inseg;
896+
intsegno;
897+
pgFile*file_item=NULL;
898+
intj;
899+
900+
segno=blkno /RELSEG_SIZE;
901+
blkno_inseg=blkno %RELSEG_SIZE;
902+
903+
rel_path=datasegpath(rnode,forknum,segno);
904+
path=pg_malloc(strlen(rel_path)+strlen(pgdata)+2);
905+
sprintf(path,"%s/%s",pgdata,rel_path);
906+
907+
for (j=0;j<parray_num(backup_files_list);j++)
908+
{
909+
pgFile*p= (pgFile*)parray_get(backup_files_list,j);
910+
911+
if (strcmp(p->path,path)==0)
912+
{
913+
file_item=p;
914+
break;
915+
}
916+
}
917+
918+
/*
919+
* If we don't have any record of this file in the file map, it means
920+
* that it's a relation that did not have much activity since the last
921+
* backup. We can safely ignore it. If it is a new relation file, the
922+
* backup would simply copy it as-is.
923+
*/
924+
if (file_item)
925+
datapagemap_add(&file_item->pagemap,blkno_inseg);
926+
927+
pg_free(path);
928+
pg_free(rel_path);
929+
}

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