PostgreSQL的 PITR实战—运用 recovery_target_time

磨砺技术珠矶，践行数据之道，追求卓越价值

回到上一级页面： PostgreSQL基础知识与基本操作索引页回到顶级页面：PostgreSQL索引页

看了很多的例子，没有发现具体讲 recovery_target_time的例子，于是自己作一个吧

在开始之前，先把postgresql.conf的配置设置好：

wal_level = archive             # minimal, archive, or hot_standby
                                # (change requires restart) # - Archiving -                                            archive_mode = on               # allows archiving to be done
                                # (change requires restart) 
 
archive_command = 'cp %p /usr/local/pgsql/arch/%f'      # command to use to archive a logfile segment
#archive_timeout =             # force a logfile segment switch after this
                                # number of seconds;  disables

然后启动PostgreSQL：

[postgres@pg201 pgsql]$ ./bin/pg_ctl -D ./data start

在开始备份前，先作一条数据：此时，时间大约是13：40之前：

postgres=# create table test(id integer);
CREATE TABLE
postgres=# insert into test values(100);
INSERT 0 1

然后开始进行基础备份：

postgres=# select pg_start_backup('gao');
 pg_start_backup
-----------------
 0/2000020
(1 row)

tar命令打包：

tar -cvf ./base.tar ./data

结束基础备份：

postgres=# select pg_stop_backup();
NOTICE:  pg_stop_backup complete, all required WAL segments have been archived
 pg_stop_backup
----------------
 0/20000A0
(1 row)

此时大约是13：40左右，再插入一条数据：

postgres=# insert into test values(200);
INSERT 0 1

等待，到13：50左右，再插入一条数据：

postgres=# insert into test values(300);
INSERT 0 1

为了方便操作，进行一次强制的日志切换：

postgres=# select pg_switch_xlog();
 pg_switch_xlog
----------------
 0/30002A0
(1 row)                postgres=#

现在，模拟崩溃，强制杀掉进程：

[root@pg201 ~]# kill -s SIGQUIT Postmaster进程号

然后，原有data目录改名保存，开始恢复过程：

[postgres@pg201 pgsql]$ mv ./data ./data.bak

[postgres@pg201 pgsql]$ tar -xvf base.tar ./data

把崩溃时后的online wal log 也准备好：

[postgres@pg201 pgsql]$ rm -rf ./data/pg_xlog
[postgres@pg201 pgsql]$ cp -r ./data.bak/pg_xlog/ ./data
[postgres@pg201 pgsql]$ cd ./data/pg_xlog
[postgres@pg201 pg_xlog]$                    [postgres@pg201 archive_status]$ pwd
/usr/local/pgsql/data/pg_xlog/archive_status
[postgres@pg201 archive_status]$ rm -f *
[postgres@pg201 archive_status]$

作一个 recovery.conf文件，指明要恢复到13：45，也就是200数据已经出现，300数据尚未插入的时候

[postgres@pg201 data]$ pwd
/usr/local/pgsql/data    [postgres@pg201 data]$ cat recovery.conf
restore_command = 'cp /usr/local/pgsql/arch/%f %p'                    recovery_target_time = '2013-08-07 13:45:00+08'                        [postgres@pg201 data]$

再次启动PostgreSQL，发生了恢复：

[postgres@pg201 pgsql]$ ./bin/pg_ctl -D ./data start
pg_ctl: another server might be running; trying to start server anyway
server starting
[postgres@pg201 pgsql]$ LOG:  database system was interrupted; last known up at -- :: CST
LOG:  starting point-in-time recovery to -- ::+
LOG:  restored log file "" from archive
LOG:  redo starts at /
LOG:  consistent recovery state reached at /
LOG:  restored log file "" from archive
LOG:  recovery stopping before commit of transaction , time -- ::05.407695+
LOG:  redo done at /
LOG:  last completed transaction was at log time -- ::44.338862+
cp: cannot stat `/usr/local/pgsql/arch/.history': No such file or directory
LOG:  selected new timeline ID:
cp: cannot stat `/usr/local/pgsql/arch/.history': No such file or directory
LOG:  archive recovery complete
LOG:  autovacuum launcher started
LOG:  database system is ready to accept connections

验证：

[postgres@pg201 ~]$ cd /usr/local/pgsql
[postgres@pg201 pgsql]$ ./bin/psql
psql (9.1.2)
Type "help" for help.postgres=# select * from test;
 id
-----
 100
 200
(2 rows)postgres=# \q

回到上一级页面： PostgreSQL基础知识与基本操作索引页回到顶级页面：PostgreSQL索引页

磨砺技术珠矶，践行数据之道，追求卓越价值