背景
苹果推出了有史以来最受欢迎的一版iOS，为什么这么受欢迎？
最主要的还是使用了最新的APFS文件系统，这个文件系统几乎集成了ZFS,Btrfs的所有优良特性，比如最为好用的快照（块级增量）、压缩。使得苹果的操作系统一下子瘦了，而且备份占用空间也非常小。
对于数据库来说，备份也不是小事，如何实现高效的备份、节省空间的备份以及具备可以定义SLA的恢复(不会随着数据库的大小、REDO的多少而变化)。
对于商业数据库来说，备份的功能一般都非常的全面。
比如Oracle，它的备份工具rman是非常强大的，很多年前就已经支持全量、增量、归档的备份模式，支持压缩等。
还支持元数据存储到数据库中，管理也非常的方便，例如保留多少归档，备份集的管理也很方便，例如要恢复到什么时间点，将此前的备份清除等等。
对于开源数据库来说，支持向商业版本这么丰富更能的比较少，PostgreSQL算是非常完善的一个。
PostgreSQL作为最高级的开源数据库，备份方面已经向商业数据库看齐。
目前PostgreSQL已经支持类似Oracle的rman备份工具的功能，支持全量、增量、归档三种备份模式，支持压缩，支持备份集的管理等。
有了块级增量备份，对于那种非常庞大的数据库，备份起来就不像只支持全量和归档的模式那么吃力了。
PostgreSQL增量备份是怎么做到的呢？
一个数据页的框架如下
* +----------------+---------------------------------+
* | PageHeaderData | linp1 linp2 linp3 ... |
* +-----------+----+---------------------------------+
* | ... linpN | |
* +-----------+--------------------------------------+
* | ^ pd_lower |
* | |
* | v pd_upper |
* +-------------+------------------------------------+
* | | tupleN ... |
* +-------------+------------------+-----------------+
* | ... tuple3 tuple2 tuple1 | "special space" |
* +--------------------------------+-----------------+
AI 代码解读
数据页头部的数据结构
typedef struct PageHeaderData
{
/* XXX LSN is member of *any* block, not only page-organized ones */
PageXLogRecPtr pd_lsn; /* LSN: next byte after last byte of xlog
* record for last change to this page */
uint16 pd_checksum; /* checksum */
uint16 pd_flags; /* flag bits, see below */
LocationIndex pd_lower; /* offset to start of free space */
LocationIndex pd_upper; /* offset to end of free space */
LocationIndex pd_special; /* offset to start of special space */
uint16 pd_pagesize_version;
TransactionId pd_prune_xid; /* oldest prunable XID, or zero if none */
ItemIdData pd_linp[FLEXIBLE_ARRAY_MEMBER]; /* line pointer array */
} PageHeaderData;
AI 代码解读
因为如果对象是持久化的，那么它的所有变更都会记录REDO，数据页头部的pd_lsn表示该数据页最后一次变化时，变化产生的REDO在xlog file中的结束位置.
即如果xlog flush的xlog地址位 大于或等于 此页pd_lsn，那么这个页的更改就可以认为是可靠的。
* pd_lsn - identifies xlog record for last change to this page.
* pd_checksum - page checksum, if set.
* pd_flags - flag bits.
* pd_lower - offset to start of free space.
* pd_upper - offset to end of free space.
* pd_special - offset to start of special space.
* pd_pagesize_version - size in bytes and page layout version number.
* pd_prune_xid - oldest XID among potentially prunable tuples on page.
AI 代码解读
好了，既然每次块的变化都包含了LSN的修改，那么也即是说，我们可以通过第一次备份开始时的全局LSN，以及当前需要备份的数据的page LSN来判断此页是否发生过修改。
如果修改了就备份，没修改，就不需要备份， 从而实现数据库的块级增量备份。
pg_rman 介绍
pg_rman是一个开源的PostgreSQL备份管理软件，类似Oracle的RMAN。
https://github.com/ossc-db/pg_rman
http://ossc-db.github.io/pg_rman/index.html
pg_rman使用的是pg_start_backup(), copy, pg_stop_backup()的备份模式。
pg_rman跑的不是流复制协议，而是文件拷贝，所以pg_rman必须和数据库节点跑在一起。
如果在standby节点跑pg_rman，pg_rman则需要通过网络连接到主节点执行pg_start_backup和pg_stop_backup。
pg_rman的用法非常简单，支持以下几种运行模式。
init
Initialize a backup catalog.
backup
Take an online backup.
restore
Do restore.
show
Show backup history. The detail option shows with additional information of each backups.
validate
Validate backup files. Backups without validation cannot be used for restore and incremental backup.
delete
Delete backup files.
purge
Remove deleted backups from backup catalog.
AI 代码解读
使用pg_rman的前提
开启归档
配置csvlog
建议的配置
postgres=# show log_destination ;
log_destination
-----------------
csvlog
(1 row)
postgres=# SHOW log_directory ;
log_directory
---------------
pg_log
(1 row)
postgres=# SHOW archive_command ;
archive_command
--------------------------------------------
cp %p /data04/digoal/arc_log/%f
(1 row)
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初始化pg_rman backup catalog
首先需要初始化一个backup catalog，实际上就是需要一个目录，这个目录将用于存放备份的文件。
同时这个目录也会存放一些元数据，例如备份的配置文件，数据库的systemid，时间线文件历史等等。
初始化命令需要两个参数，分别为备份目标目录，以及数据库的$PGDATA
$ mkdir /data05/digoal/pgbbk
$ /home/digoal/pgsql9.5/bin/pg_rman init -B /data05/digoal/pgbbk -D /data04/digoal/pg_root
INFO: ARCLOG_PATH is set to '/data04/digoal/arc_log'
INFO: SRVLOG_PATH is set to '/data04/digoal/pg_root/pg_log'
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生成备份元数据如下
[digoal@iZ28tqoemgtZ ~]$ cd /data05/digoal/pgbbk/
[digoal@iZ28tqoemgtZ pgbbk]$ ll
total 16
drwx------ 4 digoal digoal 4096 Aug 26 19:29 backup
-rw-rw-r-- 1 digoal digoal 82 Aug 26 19:29 pg_rman.ini
-rw-rw-r-- 1 digoal digoal 40 Aug 26 19:29 system_identifier
drwx------ 2 digoal digoal 4096 Aug 26 19:29 timeline_history
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生成的配置文件
$ cat pg_rman.ini
ARCLOG_PATH='/data04/digoal/arc_log'
SRVLOG_PATH='/data04/digoal/pg_root/pg_log'
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你可以把将来要使用的配置写在这个配置文件中，或者写在pg_rman的命令行中。
我后面的测试会直接使用命令行参数。
生成的数据库system id，用于区分备份的数据库是不是一个数据库，防止被冲。
$ cat system_identifier
SYSTEM_IDENTIFIER='6318621837015461309'
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与控制文件中存储的system id一致。
注意
pg_rman只从postgresql.conf取log_directory和archive_command参数的值。
如果你的PostgreSQL的配置文件是include的或者配置在postgresql.auto.conf中。
这两个值将不准确。
所以建议你仅仅把参数配置在postgresql.conf中，而不要使用其他配置文件。
pg_rman 命令行用法
pg_rman manage backup/recovery of PostgreSQL database.
Usage:
pg_rman OPTION init
pg_rman OPTION backup
pg_rman OPTION restore
pg_rman OPTION show [DATE]
pg_rman OPTION show detail [DATE]
pg_rman OPTION validate [DATE]
pg_rman OPTION delete DATE
pg_rman OPTION purge
Common Options:
-D, --pgdata=PATH location of the database storage area
-A, --arclog-path=PATH location of archive WAL storage area
-S, --srvlog-path=PATH location of server log storage area
-B, --backup-path=PATH location of the backup storage area
-c, --check show what would have been done
-v, --verbose show what detail messages
-P, --progress show progress of processed files
Backup options:
-b, --backup-mode=MODE full, incremental, or archive
-s, --with-serverlog also backup server log files
-Z, --compress-data compress data backup with zlib
-C, --smooth-checkpoint do smooth checkpoint before backup
-F, --full-backup-on-error switch to full backup mode
if pg_rman cannot find validate full backup
on current timeline
NOTE: this option is only used in --backup-mode=incremental or archive.
--keep-data-generations=NUM keep NUM generations of full data backup
--keep-data-days=NUM keep enough data backup to recover to N days ago
--keep-arclog-files=NUM keep NUM of archived WAL
--keep-arclog-days=DAY keep archived WAL modified in DAY days
--keep-srvlog-files=NUM keep NUM of serverlogs
--keep-srvlog-days=DAY keep serverlog modified in DAY days
--standby-host=HOSTNAME standby host when taking backup from standby
--standby-port=PORT standby port when taking backup from standby
Restore options:
--recovery-target-time time stamp up to which recovery will proceed
--recovery-target-xid transaction ID up to which recovery will proceed
--recovery-target-inclusive whether we stop just after the recovery target
--recovery-target-timeline recovering into a particular timeline
--hard-copy copying archivelog not symbolic link
Catalog options:
-a, --show-all show deleted backup too
Delete options:
-f, --force forcibly delete backup older than given DATE
Connection options:
-d, --dbname=DBNAME database to connect
-h, --host=HOSTNAME database server host or socket directory
-p, --port=PORT database server port
-U, --username=USERNAME user name to connect as
-w, --no-password never prompt for password
-W, --password force password prompt
Generic options:
-q, --quiet don't show any INFO or DEBUG messages
--debug show DEBUG messages
--help show this help, then exit
--version output version information, then exit
Read the website for details. <http://github.com/ossc-db/pg_rman>
Report bugs to <http://github.com/ossc-db/pg_rman/issues>.
AI 代码解读
全量备份
输入必要的参数或option
$ export PGPASSWORD=postgres
$ /home/digoal/pgsql9.5/bin/pg_rman backup \
-B /data05/digoal/pgbbk \
-D /data04/digoal/pg_root \
-b full \
-s \
-Z \
-C \
--keep-data-days=10 \
--keep-arclog-files=15 \
--keep-arclog-days=10 \
--keep-srvlog-files=10 \
--keep-srvlog-days=15 \
-h 127.0.0.1 -p 1921 -U postgres -d postgres
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结果
INFO: copying database files
NOTICE: pg_stop_backup complete, all required WAL segments have been archived
INFO: copying archived WAL files
INFO: copying server log files
INFO: backup complete
HINT: Please execute 'pg_rman validate' to verify the files are correctly copied.
INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10)
INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00"
INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15)
INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00"
INFO: start deleting old backup (keep after = 2016-08-16 00:00:00)
INFO: does not include the backup just taken
WARNING: backup "2016-08-26 19:39:32" is not taken int account
DETAIL: This is not valid backup.
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校验备份集
备份时pg_rman会记录每个备份文件的crc，以便validate进行校验。
例如某个备份集
$ less /data05/digoal/pgbbk/20160826/195809/file_database.txt
.s.PGSQL.1921 ? 0 0 0777 2016-08-26 19:27:05
.s.PGSQL.1921.lock f 55 590164837 0600 2016-08-26 19:27:05
PG_VERSION f 12 3872055064 0600 2016-07-28 10:03:42
backup_label f 167 2985542389 0600 2016-08-26 19:58:42
backup_label.old f 155 4273989468 0600 2016-08-23 19:43:32
base d 0 0 0700 2016-08-23 10:28:32
base/1 d 0 0 0700 2016-08-24 16:17:02
base/1/112 f 57 1147028285 0600 2016-07-28 10:03:42
base/1/113 f 57 1147028285 0600 2016-07-28 10:03:42
base/1/1247 F 8178 1875285513 0600 2016-07-29 13:51:29
base/1/1247_fsm f 139 3668812536 0600 2016-07-28 10:03:43
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解释
路径，文件类型，大小，CRC校验值，权限，时间
第四列即crc校验值
每次备份完，必须要做一次校验，否则备份集不可用用来恢复，增量备份时也不会用它来做增量比较。
$ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk
INFO: validate: "2016-08-26 19:39:50" backup, archive log files and server log files by CRC
INFO: backup "2016-08-26 19:39:50" is valid
AI 代码解读
每个备份集都包含了一个备份状态文件，如下
cat /data05/digoal/pgbbk/20160826/201955/backup.ini
# configuration
BACKUP_MODE=INCREMENTAL
FULL_BACKUP_ON_ERROR=false
WITH_SERVERLOG=true
COMPRESS_DATA=true
# result
TIMELINEID=1
START_LSN=46/df000108
STOP_LSN=46/df000210
START_TIME='2016-08-26 20:19:55'
END_TIME='2016-08-26 20:20:48'
RECOVERY_XID=3896508593
RECOVERY_TIME='2016-08-26 20:20:47'
TOTAL_DATA_BYTES=6196524307
READ_DATA_BYTES=3199287520
READ_ARCLOG_BYTES=33554754
READ_SRVLOG_BYTES=0
WRITE_BYTES=125955
BLOCK_SIZE=8192
XLOG_BLOCK_SIZE=8192
STATUS=OK
AI 代码解读
这个文件中包含了很重要的信息，比如LSN，后面LSN将用于比对增量备份时对比数据块的LSN是否发生了变化，是否需要备份。
增量备份
$ export PGPASSWORD=postgres
$ /home/digoal/pgsql9.5/bin/pg_rman backup \
-B /data05/digoal/pgbbk \
-D /data04/digoal/pg_root \
-b incremental \
-s \
-Z \
-C \
--keep-data-days=10 \
--keep-arclog-files=15 \
--keep-arclog-days=10 \
--keep-srvlog-files=10 \
--keep-srvlog-days=15 \
-h 127.0.0.1 -p 1921 -U postgres -d postgres
AI 代码解读
增量备份输出
INFO: copying database files
NOTICE: pg_stop_backup complete, all required WAL segments have been archived
INFO: copying archived WAL files
INFO: copying server log files
INFO: backup complete
HINT: Please execute 'pg_rman validate' to verify the files are correctly copied.
INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10)
INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00"
INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15)
INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00"
INFO: start deleting old backup (keep after = 2016-08-16 00:00:00)
INFO: does not include the backup just taken
INFO: backup "2016-08-26 19:39:50" should be kept
DETAIL: This is taken after "2016-08-16 00:00:00".
WARNING: backup "2016-08-26 19:39:32" is not taken int account
DETAIL: This is not valid backup.
AI 代码解读
校验备份集
$ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk
INFO: validate: "2016-08-26 19:43:20" backup, archive log files and server log files by CRC
INFO: backup "2016-08-26 19:43:20" is valid
AI 代码解读
列出备份集
$ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk
==========================================================
StartTime Mode Duration Size TLI Status
==========================================================
2016-08-26 19:43:20 INCR 0m 54kB 1 OK
2016-08-26 19:39:50 FULL 1m 245MB 1 OK
AI 代码解读
可以看到增量非常小，因为很少变化的块。
接下来更新一张大表的某一条记录，再看看。
postgres=# \dt+
List of relations
Schema | Name | Type | Owner | Size | Description
--------+----------+-------+----------+---------+-------------
public | hll_test | table | postgres | 208 kB |
public | t | table | postgres | 3050 MB |
public | tbl1 | table | postgres | 226 MB |
public | tbl2 | table | postgres | 63 MB |
public | test | table | postgres | 120 MB |
(5 rows)
postgres=# with t1 as (select id from t where id between 1 and 1000 limit 10) update t set info='new' where id in (select * from t1);
UPDATE 10
AI 代码解读
更新后做一个增量备份
$ /home/digoal/pgsql9.5/bin/pg_rman backup -B /data05/digoal/pgbbk -D /data04/digoal/pg_root -b incremental -s -Z -C --keep-data-days=10 --keep-arclog-files=15 --keep-arclog-days=10 --keep-srvlog-files=10 --keep-srvlog-days=15 -h 127.0.0.1 -p 1921 -U postgres -d postgres
INFO: copying database files
NOTICE: pg_stop_backup complete, all required WAL segments have been archived
INFO: copying archived WAL files
INFO: copying server log files
INFO: backup complete
HINT: Please execute 'pg_rman validate' to verify the files are correctly copied.
INFO: start deleting old archived WAL files from ARCLOG_PATH (keep files = 15, keep days = 10)
INFO: the threshold timestamp calculated by keep days is "2016-08-16 00:00:00"
INFO: start deleting old server files from SRVLOG_PATH (keep files = 10, keep days = 15)
INFO: the threshold timestamp calculated by keep days is "2016-08-11 00:00:00"
INFO: start deleting old backup (keep after = 2016-08-16 00:00:00)
INFO: does not include the backup just taken
INFO: backup "2016-08-26 19:58:09" should be kept
DETAIL: This is taken after "2016-08-16 00:00:00".
WARNING: backup "2016-08-26 19:56:54" is not taken int account
DETAIL: This is not valid backup.
INFO: backup "2016-08-26 19:43:20" should be kept
DETAIL: This is taken after "2016-08-16 00:00:00".
INFO: backup "2016-08-26 19:39:50" should be kept
DETAIL: This is taken after "2016-08-16 00:00:00".
WARNING: backup "2016-08-26 19:39:32" is not taken int account
DETAIL: This is not valid backup.
AI 代码解读
校验备份集
[digoal@iZ28tqoemgtZ pg_rman]$ /home/digoal/pgsql9.5/bin/pg_rman validate -B /data05/digoal/pgbbk
INFO: validate: "2016-08-26 20:19:55" backup, archive log files and server log files by CRC
INFO: backup "2016-08-26 20:19:55" is valid
AI 代码解读
输出当前备份
[digoal@iZ28tqoemgtZ pg_rman]$ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk
==========================================================
StartTime Mode Duration Size TLI Status
==========================================================
2016-08-26 20:19:55 INCR 0m 125kB 1 OK
2016-08-26 19:58:09 FULL 11m 3094MB 1 OK
2016-08-26 19:56:54 FULL 1m 0B 0 ERROR
2016-08-26 19:43:20 INCR 0m 54kB 1 OK
2016-08-26 19:39:50 FULL 1m 245MB 1 OK
2016-08-26 19:39:32 FULL 0m 0B 0 ERROR
AI 代码解读
增量备份的文件非常小，因为变化的数据块很少。
按指定时间从catalog删除备份集
例如我只需要我的备份集能恢复到2016-08-26 19:59:00，在这个时间点以前，不需要用来恢复到这个时间点的备份全删掉。
$ /home/digoal/pgsql9.5/bin/pg_rman delete "2016-08-26 19:59:00" -B /data05/digoal/pgbbk
WARNING: cannot delete backup with start time "2016-08-26 19:58:09"
DETAIL: This is the latest full backup necessary for successful recovery.
INFO: delete the backup with start time: "2016-08-26 19:56:54"
INFO: delete the backup with start time: "2016-08-26 19:43:20"
INFO: delete the backup with start time: "2016-08-26 19:39:50"
INFO: delete the backup with start time: "2016-08-26 19:39:32"
AI 代码解读
保留的备份集合可以将数据库恢复到2016-08-26 19:59:00
$ /home/digoal/pgsql9.5/bin/pg_rman show -B /data05/digoal/pgbbk
==========================================================
StartTime Mode Duration Size TLI Status
==========================================================
2016-08-26 20:19:55 INCR 0m 125kB 1 OK
2016-08-26 19:58:09 FULL 11m 3094MB 1 OK
AI 代码解读
物理删除已从catalog删除的备份集
$ /home/digoal/pgsql9.5/bin/pg_rman purge -B /data05/digoal/pgbbk
INFO: DELETED backup "2016-08-26 19:56:54" is purged
INFO: DELETED backup "2016-08-26 19:43:20" is purged
INFO: DELETED backup "2016-08-26 19:39:50" is purged
INFO: DELETED backup "2016-08-26 19:39:32" is purged
AI 代码解读
恢复
后续在写
pg_rman 源码浅析
1. 增量备份代码
上次备份以来，数据块的LSN是否发生了变化，如果自从上次备份的start_lsn以来没有发生变化，则不备份。
代码举例
else
{
pgBackupGetPath(prev_backup, prev_file_txt, lengthof(prev_file_txt),
DATABASE_FILE_LIST);
prev_files = dir_read_file_list(pgdata, prev_file_txt);
/*
* Do backup only pages having larger LSN than previous backup.
*/
lsn = &prev_backup->start_lsn;
xlogid = (uint32) (*lsn >> 32);
xrecoff = (uint32) *lsn;
elog(DEBUG, _("backup only the page updated after LSN(%X/%08X)"),
xlogid, xrecoff);
}
...
/* backup files from non-snapshot */
pgBackupGetPath(¤t, path, lengthof(path), DATABASE_DIR);
backup_files(pgdata, path, files, prev_files, lsn, current.compress_data, NULL);
AI 代码解读
2. 备份结果backup.ini相关代码
# configuration
BACKUP_MODE=FULL
FULL_BACKUP_ON_ERROR=false
WITH_SERVERLOG=true
COMPRESS_DATA=true
# result
TIMELINEID=1
START_LSN=43/d5000028
STOP_LSN=43/d5000168
START_TIME='2016-08-26 15:43:39'
END_TIME='2016-08-26 15:44:27'
RECOVERY_XID=3896508572
RECOVERY_TIME='2016-08-26 15:44:18'
TOTAL_DATA_BYTES=823571731
READ_DATA_BYTES=823571731
READ_ARCLOG_BYTES=234881668
READ_SRVLOG_BYTES=218248
WRITE_BYTES=206009921
BLOCK_SIZE=8192
XLOG_BLOCK_SIZE=8192
STATUS=OK
AI 代码解读
对应的数据结构
/*
* pg_rman takes backup into the directory $BACKUP_PATH/<date>/<time>.
*
* status == -1 indicates the pgBackup is invalid.
*/
typedef struct pgBackup
{
/* Backup Level */
BackupMode backup_mode;
bool with_serverlog;
bool compress_data;
bool full_backup_on_error;
/* Status - one of BACKUP_STATUS_xxx */
BackupStatus status;
/* Timestamp, etc. */
TimeLineID tli;
XLogRecPtr start_lsn;
XLogRecPtr stop_lsn;
time_t start_time;
time_t end_time;
time_t recovery_time;
uint32 recovery_xid;
/* Size (-1 means not-backup'ed) */
int64 total_data_bytes;
int64 read_data_bytes;
int64 read_arclog_bytes;
int64 read_srvlog_bytes;
int64 write_bytes;
/* data/wal block size for compatibility check */
uint32 block_size;
uint32 wal_block_size;
/* if backup from standby or not */
bool is_from_standby;
} pgBackup;
AI 代码解读
备份开始时记录pg_start_backup调用返回的lsn，写入backup->start_lsn
/*
* Notify start of backup to PostgreSQL server.
*/
static void
pg_start_backup(const char *label, bool smooth, pgBackup *backup)
{
PGresult *res;
const char *params[2];
params[0] = label;
elog(DEBUG, "executing pg_start_backup()");
reconnect();
/* Assumes PG version >= 8.4 */
/* 2nd argument is 'fast' (IOW, !smooth) */
params[1] = smooth ? "false" : "true";
res = execute("SELECT * from pg_xlogfile_name_offset(pg_start_backup($1, $2))", 2, params);
if (backup != NULL)
get_lsn(res, &backup->tli, &backup->start_lsn);
elog(DEBUG, "backup start point is (WAL file: %s, xrecoff: %s)",
PQgetvalue(res, 0, 0), PQgetvalue(res, 0, 1));
PQclear(res);
disconnect();
}
AI 代码解读
备份停止，调用pg_stop_backup，从返回结果中取出LSN，写入backup->stop_lsn
/*
* Notify end of backup to PostgreSQL server.
*/
static void
pg_stop_backup(pgBackup *backup)
{
elog(DEBUG, "executing pg_stop_backup()");
wait_for_archive(backup,
"SELECT * FROM pg_xlogfile_name_offset(pg_stop_backup())");
}
static void
wait_for_archive(pgBackup *backup, const char *sql)
{
PGresult *res;
char ready_path[MAXPGPATH];
int try_count;
reconnect();
res = execute(sql, 0, NULL);
if (backup != NULL)
{
get_lsn(res, &backup->tli, &backup->stop_lsn);
elog(DEBUG, "backup end point is (WAL file: %s, xrecoff: %s)",
PQgetvalue(res, 0, 0), PQgetvalue(res, 0, 1));
}
/* get filename from the result of pg_xlogfile_name_offset() */
elog(DEBUG, "waiting for %s is archived", PQgetvalue(res, 0, 0));
snprintf(ready_path, lengthof(ready_path),
"%s/pg_xlog/archive_status/%s.ready", pgdata, PQgetvalue(res, 0, 0));
PQclear(res);
res = execute(TXID_CURRENT_SQL, 0, NULL);
if(backup != NULL)
{
get_xid(res, &backup->recovery_xid);
backup->recovery_time = time(NULL);
}
disconnect();
/* wait until switched WAL is archived */
try_count = 0;
while (fileExists(ready_path))
{
sleep(1);
if (interrupted)
ereport(FATAL,
(errcode(ERROR_INTERRUPTED),
errmsg("interrupted during waiting for WAL archiving")));
try_count++;
if (try_count > TIMEOUT_ARCHIVE)
ereport(ERROR,
(errcode(ERROR_ARCHIVE_FAILED),
errmsg("switched WAL could not be archived in %d seconds",
TIMEOUT_ARCHIVE)));
}
elog(DEBUG, "WAL file contains backup end point is archived after %d seconds waiting",
try_count);
}
AI 代码解读
validate 时，改backup.ini的STATUS字段
validate.c
for (i = 0; i < parray_num(backup_list); i++)
{
pgBackup *backup = (pgBackup *)parray_get(backup_list, i);
/* clean extra backups (switch STATUS to ERROR) */
if(!another_pg_rman &&
(backup->status == BACKUP_STATUS_RUNNING ||
backup->status == BACKUP_STATUS_DELETING))
{
backup->status = BACKUP_STATUS_ERROR;
pgBackupWriteIni(backup);
}
/* Validate completed backups only. */
if (backup->status != BACKUP_STATUS_DONE)
continue;
/* validate with CRC value and update status to OK */
pgBackupValidate(backup, false, false, (HAVE_DATABASE(backup)));
}
...
/* update status to OK */
if (corrupted)
backup->status = BACKUP_STATUS_CORRUPT;
else
backup->status = BACKUP_STATUS_OK;
pgBackupWriteIni(backup);
AI 代码解读
注意
1.
备份参数 -C 表示无缝checkpoint, 所以可能很慢，视checkpoint_completion_target和segment_size的配置。
如果你发现pg_rman开始很慢，可以把-C去掉，速度就快了，但是可能在高峰时，造成冲击。
建议高峰是不要备份。
2.
BUG
unix socket 是$PGDATA时, validate会报错
pg_rman validate
INFO: validate: "2016-08-26 16:19:25" backup, archive log files and server log files by CRC
ERROR: invalid type '?' found in "/data05/digoal/pgbak/20160826/161925/file_database.txt"
vi /data05/digoal/pgbak/20160826/161925/file_database.txt
.s.PGSQL.1921 ? 0 0 0777 2016-08-26 15:35:05
AI 代码解读
修改一下dir.c的代码即可修复这个问题，修改如下
if (strncmp(path, ".s.PGSQL", 7) != 0 && type != 'f' && type != 'F' && type != 'd' && type != 'l')
ereport(ERROR,
(errcode(ERROR_CORRUPTED),
errmsg("invalid type '%c' found in \"%s\"", type, file_txt)));
AI 代码解读
