使用pg_basebackup搭建PostgreSQL流复制环境
接触了PostgreSQL的高可用，在这里先进行流复制实验。
环境：
OS:
[ha@node0 ~]$ uname -a
Linux node0 2.6.32-358.el6.x86_64 #1 SMP Fri Feb 22 00:31:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux
内存：1G
CPU：1核
数据库:
postgres=# select version();
version
--------------------------------------------------------------------------------
-------------------------------
PostgreSQL 9.4.5 on x86_64-unknown-linux-gnu, compiled by gcc (GCC) 4.4.7 20120
313 (Red Hat 4.4.7-16), 64-bit
(1 row)
postgres=#
.bash_profile
[ha@node0 ~]$ cat .bash_profile
# .bash_profile
# Get the aliases and functions
if [ -f ~/.bashrc ]; then
. ~/.bashrc
fi
# User specific environment and startup programs
export PGHOME=/home/ha/pgdb/
export PGDATA=/home/ha/pgdb/data/
export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$PGHOME/lib/
export PATH=$PGHOME/bin:$PATH:$HOME/bin
搭建过程：
1.主库配置
a.postgresql.conf：
listen_addresses = '*'
wal_level = hot_standby
archive_mode = off
max_wal_senders = 3
wal_keep_segments = 16
这里要说明的是参数archive_mode，我在实验过程中有一次发现参数archive_mode和archive_command在不设置的情况下也可以完成流复制，所以我对此进行了调研，发现francs已经对此进行了解释，这里引用francs的结论：
“ 在搭建流复制环境时，并不必须设置 archive_mode 参数为 on ，很多资料在介绍搭建流复制环境时设置这个参数为 on ，可能是出于开启 WAL 归档更安全的原因，因为在主库宕机并且较长时间不能恢复时，从库依然可以读取归档目录的 WAL，从而保证不丢数据; 另一方面，如果主库设置了较大的 wal_keep_segments ，也可以不用开启archive_mode，因为主库保留了足够的 WAL，从而大大降低了因从库所需要的 WAL 被主库覆盖而需要从归档去取 WAL 的情况。所以从这方面说，archive_mode 参数的设置与搭建流复制并没有直接关系。 提示： 对于比较繁忙的库，在搭建流复制从库时，建议主库设置较大的 wal_keep_segments 参数。 ”
b.pg_hba.conf
host all all 192.168.238.0/24 md5
host replication rep 192.168.238.0/24 trust
这里说明的是，网上有其他对replication设置为md5，并建立.pgpass文件，这种方法也是可行的。
c.新建用户rep
create user rep replication encrypted password 'rep';
2.使用pg_basebackup进行从库备份
[ha@localhost pgdb]$ pg_basebackup -D $PGDATA -F p -X stream -v -P -h 192.168.238.130 -U rep
transaction log start point: 0/2000028 on timeline 1
pg_basebackup: starting background WAL receiver
20945/20945 kB (100%), 1/1 tablespace
transaction log end point: 0/20000F0
pg_basebackup: waiting for background process to finish streaming ...
pg_basebackup: base backup completed
[ha@localhost pgdb]$ ll
total 20
drwxrwxr-x. 2 ha ha 4096 Dec 26 00:54 bin
drwx------. 18 ha ha 4096 Dec 26 12:02 data
drwxrwxr-x. 4 ha ha 4096 Dec 26 00:54 include
drwxrwxr-x. 4 ha ha 4096 Dec 26 00:54 lib
drwxrwxr-x. 4 ha ha 4096 Dec 26 00:54 share
[ha@localhost pgdb]$ cd data/
[ha@localhost data]$ ls
backup_label pg_hba.conf pg_replslot pg_subtrans postgresql.auto.conf
base pg_ident.conf pg_serial pg_tblspc postgresql.conf
global pg_logical pg_snapshots pg_twophase
pg_clog pg_multixact pg_stat PG_VERSION
pg_dynshmem pg_notify pg_stat_tmp pg_xlog
这里需要对目录进行一下说明：data目录可以通过pg_basebackup自动创建，但是其他表空间，需要手动创建并赋权，这里需要注意的是，权限为700。
3.从库配置
a.postgresql.conf
hot_standby = on
b.recovery.conf
standby_mode = on
primary_conninfo = 'host=192.168.238.130 port=5432 user=rep'
trigger_file = '/home/ha/pgdb/pg.trigger.file'
4.备库启动前，主库进程
[ha@localhost pgdb]$ ps -ef | grep post
root 2124 1 0 04:47 ? 00:00:00 /usr/libexec/postfix/master
postfix 2147 2124 0 04:47 ? 00:00:00 qmgr -l -t fifo -u
postfix 10385 2124 0 11:27 ? 00:00:00 pickup -l -t fifo -u
ha 10691 1 0 12:33 pts/3 00:00:00 /home/ha/pgdb/bin/postgres_ora
ha 10693 10691 0 12:33 ? 00:00:00 postgres: checkpointer process
ha 10694 10691 0 12:33 ? 00:00:00 postgres: writer process
ha 10695 10691 0 12:33 ? 00:00:00 postgres: wal writer process
ha 10696 10691 0 12:33 ? 00:00:00 postgres: autovacuum launcher process
ha 10697 10691 0 12:33 ? 00:00:00 postgres: stats collector process
ha 10717 4087 0 12:37 pts/3 00:00:00 grep post
5.备库启动后
a.主库进程
[ha@localhost pgdb]$ ps -ef | grep post
root 2124 1 0 04:47 ? 00:00:00 /usr/libexec/postfix/master
postfix 2147 2124 0 04:47 ? 00:00:00 qmgr -l -t fifo -u
postfix 10385 2124 0 11:27 ? 00:00:00 pickup -l -t fifo -u
ha 10691 1 0 12:33 pts/3 00:00:00 /home/ha/pgdb/bin/postgres_ora
ha 10693 10691 0 12:33 ? 00:00:00 postgres: checkpointer process
ha 10694 10691 0 12:33 ? 00:00:00 postgres: writer process
ha 10695 10691 0 12:33 ? 00:00:00 postgres: wal writer process
ha 10696 10691 0 12:33 ? 00:00:00 postgres: autovacuum launcher process
ha 10697 10691 0 12:33 ? 00:00:00 postgres: stats collector process
ha 10718 10691 0 12:37 ? 00:00:00 postgres: wal sender process rep 192.168.238.131(59195) streaming 0/3000060
ha 10720 4087 0 12:37 pts/3 00:00:00 grep post
b.备库进程
[ha@localhost data]$ ps -ef | grep post
root 2086 1 0 04:48 ? 00:00:00 /usr/libexec/postfix/master
postfix 2108 2086 0 04:48 ? 00:00:00 qmgr -l -t fifo -u
postfix 9657 2086 0 11:27 ? 00:00:00 pickup -l -t fifo -u
ha 9782 1 0 12:36 pts/2 00:00:00 /home/ha/pgdb/bin/postgres
ha 9783 9782 0 12:36 ? 00:00:00 postgres: startup process recovering 000000010000000000000003
ha 9784 9782 0 12:36 ? 00:00:00 postgres: checkpointer process
ha 9785 9782 0 12:36 ? 00:00:00 postgres: writer process
ha 9786 9782 0 12:36 ? 00:00:00 postgres: stats collector process
ha 9787 9782 0 12:36 ? 00:00:00 postgres: wal receiver process streaming 0/3000060
ha 9792 3744 0 12:37 pts/2 00:00:00 grep post
6.实验效果
a.主库
[ha@localhost pgdb]$ psql postgres
psql (9.4.5)
Type "help" for help.
postgres=# create table test(id int);
CREATE TABLE
postgres=# insert into test values (1),(2);
INSERT 0 2
postgres=# select * from test ;
id
----
1
2
(2 rows)
postgres=#
b.备库
[ha@localhost data]$ psql postgres
psql (9.4.5)
Type "help" for help.
postgres=# select * from test ;
id
----
1
2
(2 rows)
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