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postgres的增量恢复

DBA童鞋对增量恢复的概念一定很熟悉，与MySQL的增量恢复类似，使用“t1时刻的全备”+“t1至t2时刻的wal日志”，即可将postgres恢复至t2时刻。

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前期准备：
配置postgres.conf：
wal_level=archive 或 hot_standby 或 更高级别
archive_mode = on
archive_command='DATE=date +%Y%m%d;DIR="/paic/pg6666/pg_archlog/$DATE";(test -d $DIR || mkdir -p $DIR) && cp %p $DIR/%f'

备份脚本backup.sh：

#!/bin/bash 

export LANG=en_US.utf8 
export PGHOME=/paic/postgres/base/9.4.0 
export LD_LIBRARY_PATH=$PGHOME/lib:/lib64:/usr/lib64:/usr/local/lib64:/lib:/usr/lib:/usr/local/lib:$LD_LIBRARY_PATH 
export DATE=`date +"%Y%m%d"` 
export PATH=$PGHOME/bin:$PATH:. 
export PGDATA=/paic/pg6666/data

BASEDIR="/paic/postgres/home/postgres/pg_bak" 

date +%F-%T 

if [ ! -d $BASEDIR/$DATE ]; then 
  mkdir -p $BASEDIR/$DATE 
  if [ $? -eq 0 ]; then 
    psql -h 127.0.0.1 -p 6666 -U postgres postgres -c "select pg_start_backup(now()::text)" 
    if [ $? -eq 0 ]; then 
      cp -r -L $PGDATA $BASEDIR/$DATE 
    else 
      echo -e "select pg_start_backup(now()::text) error" 
      exit 1 
    fi 
    psql -h 127.0.0.1 -p 6666 -U postgres postgres -c "select pg_stop_backup()" 
    date +%F-%T 
    echo -e "backup successed" 
    exit 0 
  else 
    echo -e "mkdir -p $BASEDIR/$DATE error" 
    exit 1 
  fi 
else 
  echo -e "$DATE backuped, don't backup repeated" 
  exit 1 
fi

恢复脚本recovery.sh:

#!/bin/bash 
export LANG=en_US.utf8 
export PGHOME=/paic/postgres/base/9.4.0 
export LD_LIBRARY_PATH=$PGHOME/lib:/lib64:/usr/lib64:/usr/local/lib64:/lib:/usr/lib:/usr/local/lib:$LD_LIBRARY_PATH 
export PATH=$PGHOME/bin:$PATH:. 
export PGDATA=/paic/pg6666/data
export DATE=`date +"%Y%m%d"`

if [ -z "$1" ]; then
  echo "1st argument is empty!"
else
  if [ -z "$2" ]; then
    echo "2nd argument is empty!"
  else
    if [ -f $PGDATA/postmaster.pid ]; then
      echo "shutdown database first!"
    else 
      cd $PGDATA
      rm -rf *
      cp -r /paic/postgres/home/postgres/pg_bak/$DATE/data/* $PGDATA/
      cd $PGDATA/pg_xlog
      rm -rf *
      cd $PGDATA
      cp $PGHOME/share/recovery.conf.sample ./recovery.conf
      echo restore_command = \'cp /paic/pg6666/pg_archlog/$DATE/%f %p\' >> ./recovery.conf
      echo recovery_target_time = \'$1 $2\' >> ./recovery.conf
      pg_ctl start
    fi
  fi
fi

backup.sh和recovery.sh中的目录请自行修改。

模拟故障恢复：
1.准备阶段
-bash-4.1$ psql
psql (9.4.0)
Type "help" for help.
postgres=# \c mydb alex
You are now connected to database "mydb" as user "alex".
确认数据库初始状态
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | test | table | alex
(1 row)
此时mydb数据库只有test表

创建aaa
mydb=# create table aaa(id int);
CREATE TABLE
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | test | table | alex
(2 rows)
mydb=# checkpoint; --确保修改写入文件（非必须）
CHECKPOINT
mydb=# select pg_switch_xlog(); --确保修改写入归档（非必须）
pg_switch_xlog
·····················
0/E6000120
(1 row)
上述操作于2017-12-22 13:52:00前完成

接着在2017-12-22 13:53:00时，创建表bbb
mydb=# create table bbb(id int);
CREATE TABLE
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | bbb | table | alex
public | test | table | alex
(3 rows)
mydb=# checkpoint;
CHECKPOINT
mydb=# select pg_switch_xlog();
pg_switch_xlog
·····················
0/E7013FC0
(1 row)
mydb=# \q
上述操作于2017-12-22 13:54:00前完成

2.现在尝试回滚数据库至指定时间点
-bash-4.1$ pg_ctl stop -m fast
waiting for server to shut down..... done
server stopped
-bash-4.1$ cd --我的recovery.sh 文件放在home目录，所以需切换目录
-bash-4.1$ . recovery.sh 2017-12-22 13:52:00 --传入时间参数$1:2017-12-22, $2:13:52:00 并执行脚本
pg_ctl: another server might be running; trying to start server anyway
server starting
-bash-4.1$ 2017-12-22 13:54:26 HKT:undefined:[13323]: LOG: redirecting log output to logging collector process
2017-12-22 13:54:26 HKT:undefined:[13323]: HINT: Future log output will appear in directory "/paic/pg6666/data/pg_log".
-bash-4.1$
-bash-4.1$
-bash-4.1$ psql
psql (9.4.0)
Type "help" for help.
postgres=# \c mydb alex
You are now connected to database "mydb" as user "alex".
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | test | table | alex
(2 rows)
mydb=# \q
可知目前数据库已回滚至2017-12-22 13:52:00时，刚创建完表aaa状态

继续测试
-bash-4.1$ pg_ctl stop
waiting for server to shut down.... done
server stopped
-bash-4.1$ cd
-bash-4.1$ . recovery.sh 2017-12-22 13:53:10
pg_ctl: another server might be running; trying to start server anyway
server starting
-bash-4.1$ 2017-12-22 13:56:39 HKT:undefined:[13390]: LOG: redirecting log output to logging collector process
2017-12-22 13:56:39 HKT:undefined:[13390]: HINT: Future log output will appear in directory "/paic/pg6666/data/pg_log".
-bash-4.1$
-bash-4.1$ psql
psql (9.4.0)
Type "help" for help.
postgres=# \c mydb alex
You are now connected to database "mydb" as user "alex".
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | bbb | table | alex
public | test | table | alex
(3 rows)
可知目前数据库已回滚至2017-12-22 13:53:10时，刚创建完表bbb的状态

3.现在模拟删表误操作的回滚
2017-12-22 14:01:00 删除表test
mydb=# drop table test;
DROP TABLE
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | bbb | table | alex
mydb=# checkpoint;
CHECKPOINT
mydb=# select pg_switch_xlog();
pg_switch_xlog
·····················
0/E9005140
(1 row)
mydb=# \q

执行recovery.sh回滚数据库
-bash-4.1$ pg_ctl stop
waiting for server to shut down.... done
server stopped
-bash-4.1$ cd
-bash-4.1$ . recovery.sh 2017-12-22 14:00:00
pg_ctl: another server might be running; trying to start server anyway
server starting
-bash-4.1$ 2017-12-22 14:02:09 HKT:undefined:[13583]: LOG: redirecting log output to logging collector process
2017-12-22 14:02:09 HKT:undefined:[13583]: HINT: Future log output will appear in directory "/paic/pg6666/data/pg_log".
-bash-4.1$
-bash-4.1$ psql
psql (9.4.0)
Type "help" for help.
postgres=# \c mydb alex
You are now connected to database "mydb" as user "alex".
mydb=# \d
List of relations
Schema | Name | Type | Owner
--------+------+-------+-------
public | aaa | table | alex
public | bbb | table | alex
public | test | table | alex
(3 rows)
可知目前数据库已回滚至2017-12-22 13:14:00时，表test未被删除的状态

本实验仅限在测试环境模拟，有助于理解postgres的备份恢复机制，禁止用于生产！


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