HighGo Database判断流复制主备角色的方法

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详细信息

文档用途

HighGo Database数据库流复制判断主备角色

详细信息

进行流复制主备切换之前首先要知道当前数据库的角色，以下提供五种方法判断数据库角色，测试环境为一主一备。

1.通过pg_controldata命令查看数据库的控制信息，Database cluster state字段信息可判断是主库还是备库。

主库返回in production：

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[highgo@localhost ~]$ pg_controldata |grep cluster
Database cluster state:               in production

备库返回in archive recovery：

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[highgo@localhost ~]$ pg_controldata |grep cluster
Database cluster state:               in archive recovery

2.通过进程查看，ps -ef | grep wal | grep -v grep。

显示wal sender ...streaming进程说明当前数据库为主库：

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[highgo@localhost ~]$ ps -ef | grep wal | grep -v grep
highgo    10625  10239  0 07:03 ?        00:00:00 postgres: wal writer process  
highgo    14540  10239  0 10:00 ?        00:00:00 postgres: wal sender process repuser x.x.150.163(63146) streaming 0/100991F8

显示wal receive ...streaming说明当前数据库为备库：

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[highgo@localhost ~]$ ps -ef | grep wal | grep -v grep
highgo    18692  18687  0 10:00 ?        00:00:00 postgres: wal receiver process   streaming 0/100991F8

3.通过查看数据字典表pg_stat_replication。进入psql客户端，输入select * from pg_stat_replication;

主库在表中能查到记录：

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[highgo@localhost ~]$ psql
psql (4.7.6)

PSQL: Release 4.7.6
Connected to:
HighGo Database V4.7 Standard Edition Release 4.7.6 - 64-bit Production

Type "help" for help.

highgo=# select * from pg_stat_replication;
  pid  | usesysid | usename | application_name |   client_addr   | client_hostna
me | client_port |         backend_start         | backend_xmin |   state   | se
nt_location | write_location | flush_location | replay_location | sync_priority
| sync_state
-------+----------+---------+------------------+-----------------+--------------
---+-------------+-------------------------------+--------------+-----------+---
------------+----------------+----------------+-----------------+---------------
+------------
 14540 |    16384 | repuser | walreceiver      | x.x.150.163 |             
   |       63146 | 2019-01-10 10:00:23.252552+08 |              | streaming | 0/
100991F8    | 0/100991F8     | 0/100991F8     | 0/100991F8      |             0
| async
(1 row)

备库在表中无记录：

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highgo=#  select * from pg_stat_replication;
 pid | usesysid | usename | application_name | client_addr | client_hostname | c
lient_port | backend_start | backend_xmin | state | sent_location | write_locati
on | flush_location | replay_location | sync_priority | sync_state
-----+----------+---------+------------------+-------------+-----------------+--
-----------+---------------+--------------+-------+---------------+-------------
---+----------------+-----------------+---------------+------------
(0 rows)

4.通过系统函数pg_is_in_recovery()判断。

进入psql客户端，输入select pg_is_in_recovery();

主库返回：

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highgo=# select pg_is_in_recovery();
 pg_is_in_recovery
-------------------
 f
(1 row)

备库返回t：

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highgo=# select pg_is_in_recovery();
 pg_is_in_recovery
-------------------
 t
(1 row)

5.通过recovery.conf配置文件判断。

进入$PGDATA目录，存在recovery.conf配置文件说明是备库：

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[highgo@localhost ~]$ cd $PGDATA
[highgo@localhost data]$ ls
backup_label.old  pg_dynshmem    pg_snapshots  postgresql.auto.conf
base              pg_hba.conf    pg_stat       postgresql.conf
data.tar.gz       pg_ident.conf  pg_stat_tmp   postmaster.opts
global            pg_logical     pg_subtrans   postmaster.pid
hgdb.lic          pg_multixact   pg_tblspc     recovery.conf
hgdb_log          pg_notify      pg_twophase
pg_clog           pg_replslot    PG_VERSION
pg_commit_ts      pg_serial      pg_xlog

不存在recovery.conf或此文件后缀名是recovery.done说明是主库。

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[highgo@localhost ~]$ cd $PGDATA
[highgo@localhost data]$ ls
backup_label.old  pg_commit_ts   pg_serial     pg_xlog
base              pg_dynshmem    pg_snapshots  postgresql.auto.conf
data.tar.gz       pg_hba.conf    pg_stat       postgresql.conf
global            pg_ident.conf  pg_stat_tmp   postmaster.opts
hgdb.lic          pg_logical     pg_subtrans   postmaster.pid
hgdb_log          pg_multixact   pg_tblspc
NIH               pg_notify      pg_twophase
pg_clog           pg_replslot    PG_VERSION