Postgresql - Point In Time Recovery (PITR)

最新推荐文章于 2025-05-13 16:34:59 发布

原创最新推荐文章于 2025-05-13 16:34:59 发布 · 510 阅读

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#Postgresql #PITR #时间点恢复 #Point In Time Recovery

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博客介绍了数据库PITR技术，其原理是基于物理备份文件和wal预写日志模式备份进行恢复。并通过CentOS 7 + PG 10.8环境做实验，展示了从初始化数据库、配置参数、备份、测试数据，到模拟故障恢复、推进恢复进度，最后开启读写模式的完整过程。

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数据库的PITR是一般数据库都必须满足的技术。其原理是依据之前的物理备份文件加上wal的预写日志模式备份做的恢复。

直接拿实验说话：

环境 CentOS 7 + PG 10.8

0. 初始化数据库

initdb -D /usr/local/pgsql/data/
......
Success. You can now start the database server using:
    pg_ctl -D /usr/local/pgsql/data/ -l logfile start
service postgresql_5432 start

psql -U postgres

postgres=# create user dbadmin superuser ;
CREATE ROLE
postgres=# create user mytest superuser ;
CREATE ROLE
postgres=# create database mytest owner mytest;
CREATE DATABASE

1. 配置参数

vim postgresql.conf

archive_mode = on     
archive_command = 'cp %p /home/postgres/pg_wal/%f'   
archive_timeout = 3600
wal_level = replica

service postgresql_5432 restart

2. 备份

su - postgres
mkdir /home/postgres/backup/
pg_basebackup -Ft -X -D /home/postgres/backup/

3. 测试数据

mytest=# create table test (id serial primary key, col varchar(1000), ctime timestamp without time zone default now());
CREATE TABLE
insert into test (col) values ('a');
insert into test (col) values ('b');
insert into test (col) values ('c');

mytest=# select * from test;
 id | col |           ctime
----+-----+----------------------------
  1 | a   | 2019-06-18 03:57:12.767601
  2 | b   | 2019-06-18 03:57:12.772068
  3 | c   | 2019-06-18 03:57:13.572814
  4 | a   | 2019-06-18 03:57:14.982699
  5 | b   | 2019-06-18 03:57:14.985398
  6 | c   | 2019-06-18 03:57:16.181587
  7 | a   | 2019-06-18 03:57:20.958266
  8 | b   | 2019-06-18 03:57:20.960301
  9 | c   | 2019-06-18 03:57:21.653256
(9 rows)

mytest=# select pg_switch_wal();
 pg_switch_wal
---------------
 0/30251D0
(1 row)

4. 删除数据库

模拟数据库宕机或修改错误数据

service postgresql_5432 stop
rm -rf /usr/local/pgsql/data/*

5. 恢复

5.1 解压基础备份文件

找到备份文件

cd /home/postgres/backup/
tar xvf base.tar -C /usr/local/pgsql/data/
tar xvf pg_wal.tar -C /usr/local/pgsql/data/

5.2 配置恢复文件 recovery.conf

vim recovery.conf
restore_command = 'cp /home/postgres/pg_wal/%f %p'
recovery_target_time = '2019-06-18 03:57:13.572814'

chown -R postgres:postgres recovery.conf
chmod 700 /var/lib/pgsql/10/data
chmod 700 /usr/local/pgsql/data

5.3 启动

service postgresql_5432 start

6. 查看

mytest=# select * from test;
 id | col |           ctime
----+-----+----------------------------
  1 | a   | 2019-06-18 03:57:12.767601
  2 | b   | 2019-06-18 03:57:12.772068
(2 rows)

7. 向前推进

7.1

service postgresql_5432 stop
vim recovery.conf
restore_command = 'cp /home/postgres/pg_wal/%f %p'
recovery_target_time = '2019-06-18 03:57:14'

观察日志

2019-06-18 04:10:29.787 EDT [24681] LOG:  database system was shut down in recovery at 2019-06-18 04:09:37 EDT
2019-06-18 04:10:29.788 EDT [24681] LOG:  starting point-in-time recovery to 2019-06-18 03:57:14-04
2019-06-18 04:10:29.841 EDT [24681] LOG:  restored log file "000000010000000000000002" from archive
2019-06-18 04:10:29.895 EDT [24681] LOG:  redo starts at 0/2000060
2019-06-18 04:10:29.943 EDT [24681] LOG:  restored log file "000000010000000000000003" from archive
2019-06-18 04:10:29.996 EDT [24681] LOG:  consistent recovery state reached at 0/3024D00
2019-06-18 04:10:29.996 EDT [24681] LOG:  recovery stopping before commit of transaction 568, time 2019-06-18 03:57:14.983236-04
2019-06-18 04:10:29.996 EDT [24681] LOG:  recovery has paused
2019-06-18 04:10:29.996 EDT [24681] HINT:  Execute pg_wal_replay_resume() to continue.
2019-06-18 04:10:29.998 EDT [24679] LOG:  database system is ready to accept read only connections

7.2

mytest=# select * from test;
 id | col |           ctime
----+-----+----------------------------
  1 | a   | 2019-06-18 03:57:12.767601
  2 | b   | 2019-06-18 03:57:12.772068
  3 | c   | 2019-06-18 03:57:13.572814
(3 rows)

7.3 继续推进

service postgresql_5432 stop

vim recovery.conf
restore_command = 'cp /home/postgres/pg_wal/%f %p'
recovery_target_time = '2019-06-18 03:57:17'

service postgresql_5432 start

mytest=# select * from test;
 id | col |           ctime
----+-----+----------------------------
  1 | a   | 2019-06-18 03:57:12.767601
  2 | b   | 2019-06-18 03:57:12.772068
  3 | c   | 2019-06-18 03:57:13.572814
  4 | a   | 2019-06-18 03:57:14.982699
  5 | b   | 2019-06-18 03:57:14.985398
  6 | c   | 2019-06-18 03:57:16.181587
(6 rows)

log

2019-06-18 04:13:27.951 EDT [25020] LOG:  database system was shut down in recovery at 2019-06-18 04:13:16 EDT
2019-06-18 04:13:27.952 EDT [25020] LOG:  starting point-in-time recovery to 2019-06-18 03:57:17-04
2019-06-18 04:13:27.997 EDT [25020] LOG:  restored log file "000000010000000000000002" from archive
2019-06-18 04:13:28.054 EDT [25020] LOG:  redo starts at 0/2000060
2019-06-18 04:13:28.103 EDT [25020] LOG:  restored log file "000000010000000000000003" from archive
2019-06-18 04:13:28.157 EDT [25020] LOG:  consistent recovery state reached at 0/3024DB0
2019-06-18 04:13:28.158 EDT [25020] LOG:  recovery stopping before commit of transaction 571, time 2019-06-18 03:57:20.958823-04
2019-06-18 04:13:28.158 EDT [25020] LOG:  recovery has paused
2019-06-18 04:13:28.158 EDT [25020] HINT:  Execute pg_wal_replay_resume() to continue.
2019-06-18 04:13:28.159 EDT [25018] LOG:  database system is ready to accept read only connections

8. 开启读写模式

如果我们确定恢复完成之后，可以打开读写模式了。只需要执行 pg_wal_replay_resume()

mytest=# create table test0618 (id int);
ERROR:  cannot execute CREATE TABLE in a read-only transaction

mytest=# select pg_is_in_recovery();
 pg_is_in_recovery
-------------------
 t
(1 row)
mytest=# select * from pg_wal_replay_resume();
 pg_wal_replay_resume
----------------------
(1 row)
mytest=# select pg_is_in_recovery();
 pg_is_in_recovery
-------------------
 f
(1 row)
mytest=#  create table test0618 (id int);
CREATE TABLE