PostgreSQL几种启动方式测试

参考：

https://www.postgresql.org/docs/11/server-start.html#SERVER-START-FAILURES
https://www.postgresql.org/docs/11/reference-server.html

总结：

1、前台启动 postgres或者postmaster
2、后台启动 pg_ctl

先来说一说，何谓前台启动，可以从以下的演示看出，单纯的使用postgres命令启动数据库，当前会话终止或者断开后数据库就会自动关闭。

[postgresql@tidb63 ~]$ /usr/local/pgsql/bin/postgres 
2020-08-19 17:00:13.393 CST [122585] LOG:  listening on IPv4 address "0.0.0.0", port 5432
2020-08-19 17:00:13.393 CST [122585] LOG:  listening on IPv6 address "::", port 5432
2020-08-19 17:00:13.394 CST [122585] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
2020-08-19 17:00:13.406 CST [122586] LOG:  database system was shut down at 2020-08-19 16:59:12 CST
2020-08-19 17:00:13.412 CST [122585] LOG:  database system is ready to accept connections

^C2020-08-19 17:00:32.767 CST [122585] LOG:  received fast shutdown request
2020-08-19 17:00:32.767 CST [122585] LOG:  aborting any active transactions
2020-08-19 17:00:32.767 CST [122585] LOG:  background worker "logical replication launcher" (PID 122593) exited with exit code 1
2020-08-19 17:00:32.767 CST [122587] LOG:  shutting down
2020-08-19 17:00:32.826 CST [122585] LOG:  database system is shut down
[postgresql@tidb63 ~]$ 

所以，如果要使用postgres命令启动PostgreSQL实例，需要放在使用"&" 放在后台执行。

[postgresql@tidb63 ~]$ nohup /usr/local/pgsql/bin/postgres -D $PGDATA &
[1] 130040
[postgresql@tidb63 ~]$ nohup: 忽略输入并把输出追加到"nohup.out"
[postgresql@tidb63 ~]$ ps -ef | grep postgres | egrep -v 'grep|su'
postgre+ 130040  90407  0 17:20 pts/4    00:00:00 /usr/local/pgsql/bin/postgres -D /home/jm/pg118/pg5432/data
postgre+ 130042 130040  0 17:20 ?        00:00:00 postgres: checkpointer   
postgre+ 130043 130040  0 17:20 ?        00:00:00 postgres: background writer   
postgre+ 130044 130040  0 17:20 ?        00:00:00 postgres: walwriter   
postgre+ 130045 130040  0 17:20 ?        00:00:00 postgres: autovacuum launcher   
postgre+ 130046 130040  0 17:20 ?        00:00:00 postgres: archiver   
postgre+ 130047 130040  0 17:20 ?        00:00:00 postgres: stats collector   
postgre+ 130048 130040  0 17:20 ?        00:00:00 postgres: logical replication launcher   
[postgresql@tidb63 ~]$ pg_ctl stop -D $PGDATA -m fast
waiting for server to shut down.... done
server stopped
[1]+  完成                  nohup /usr/local/pgsql/bin/postgres -D $PGDATA

从以上可以看出前台命令启动的pg,仍然可以使用pg_ctl命令进行关闭。

可以看出postmaster其实是postgres的一个软链接。

 

[postgresql@tidb63 bin]$ pwd
/usr/local/pgsql/bin
[postgresql@tidb63 bin]$ ls -l post*
-rwxr-xr-x. 1 root root 7931144 7月  28 16:37 postgres
lrwxrwxrwx. 1 root root       8 7月  28 16:37 postmaster -> postgres
[postgresql@tidb63 bin]$ cd
[postgresql@tidb63 ~]$ nohup /usr/local/pgsql/bin/postmaster  -D $PGDATA &
[1] 131283
[postgresql@tidb63 ~]$ nohup: 忽略输入并把输出追加到"nohup.out"

[postgresql@tidb63 ~]$ ps -ef | grep postgres | egrep -v 'grep|su'
postgre+ 131285 131283  0 17:24 ?        00:00:00 postgres: checkpointer   
postgre+ 131286 131283  0 17:24 ?        00:00:00 postgres: background writer   
postgre+ 131287 131283  0 17:24 ?        00:00:00 postgres: walwriter   
postgre+ 131288 131283  0 17:24 ?        00:00:00 postgres: autovacuum launcher   
postgre+ 131289 131283  0 17:24 ?        00:00:00 postgres: archiver   
postgre+ 131290 131283  0 17:24 ?        00:00:00 postgres: stats collector   
postgre+ 131291 131283  0 17:24 ?        00:00:00 postgres: logical replication launcher   
[postgresql@tidb63 ~]$ pg_ctl stop -D $PGDATA -m fast
waiting for server to shut down.... done
server stopped
[1]+  完成                  nohup /usr/local/pgsql/bin/postmaster -D $PGDATA
[postgresql@tidb63 ~]$ [postgresql@tidb63 ~]$ nohup /usr/local/pgsql/bin/postmaster  -D $PGDATA &
[1] 131283
[postgresql@tidb63 ~]$ nohup: 忽略输入并把输出追加到"nohup.out"

配置systemd服务启停

[root@tidb63 system]# pwd
/usr/lib/systemd/system
[root@tidb63 system]# cat pg118.service 
[Unit]
Description=PostgreSQL 11.8 database server


[Service]
Type=forking
User=postgresql
ExecStart=/usr/local/pgsql/bin/pg_ctl start -D /home/jm/pg118/pg5432/data -l /tmp/logfile
ExecStop=/usr/local/pgsql/bin/pg_ctl stop -D /home/jm/pg118/pg5432/data -l /tmp/logfile
TimeoutSec=0

[Install]
WantedBy=multi-user.target

说明：官方文档中提到，Using Type=notify requires that the server binary was built with configure --with-systemd. 

测试的时候，如果使用的是pg_ctl后台启动，编译的时候并没有指定---with-systemd，也是可以用服务进行管理的，注意需要安装：systemd-devel.x86_64

[postgresql@tidb63 ~]$ pg_config --configure
'--prefix=/usr/local/pgsql' '--with-pgport=5432'
[postgresql@tidb63 ~]$ 

[root@tidb63 system]# systemctl daemon-reload
[root@tidb63 system]# systemctl start pg118.service 
[root@tidb63 system]# systemctl status pg118.service 
● pg118.service - PostgreSQL 11.8 database server
   Loaded: loaded (/usr/lib/systemd/system/pg118.service; disabled; vendor preset: disabled)
   Active: active (running) since 四 2020-08-20 13:41:06 CST; 1s ago
  Process: 148181 ExecStart=/usr/local/pgsql/bin/pg_ctl start -D /home/jm/pg118/pg5432/data -l /tmp/logfile (code=exited, status=0/SUCCESS)
 Main PID: 148183 (postgres)
    Tasks: 8
   Memory: 13.4M
   CGroup: /system.slice/pg118.service
           ├─148183 /usr/local/pgsql/bin/postgres -D /home/jm/pg118/pg5432/data
           ├─148185 postgres: checkpointer   
           ├─148186 postgres: background writer   
           ├─148187 postgres: walwriter   
           ├─148188 postgres: autovacuum launcher   
           ├─148189 postgres: archiver   
           ├─148190 postgres: stats collector   
           └─148191 postgres: logical replication launcher   

8月 20 13:41:06 tidb63.com systemd[1]: Starting PostgreSQL 11.8 database server...
8月 20 13:41:06 tidb63.com systemd[1]: Started PostgreSQL 11.8 database server.
[root@tidb63 system]# 
[root@tidb63 system]# systemctl stop pg118.service 
[root@tidb63 system]# systemctl status pg118.service 
● pg118.service - PostgreSQL 11.8 database server
   Loaded: loaded (/usr/lib/systemd/system/pg118.service; disabled; vendor preset: disabled)
   Active: inactive (dead)

8月 20 11:58:01 tidb63.com pg_ctl[117065]: 2020-08-20 11:58:01.449 CST [117067] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"
8月 20 11:58:01 tidb63.com pg_ctl[117065]: 2020-08-20 11:58:01.464 CST [117068] LOG:  database system was shut down at 2020...46 CST
8月 20 11:58:01 tidb63.com pg_ctl[117065]: 2020-08-20 11:58:01.466 CST [117067] LOG:  database system is ready to accept connections
8月 20 11:58:01 tidb63.com systemd[1]: Started PostgreSQL 11.8 database server.
8月 20 13:40:39 tidb63.com systemd[1]: Stopping PostgreSQL 11.8 database server...
8月 20 13:40:39 tidb63.com systemd[1]: Stopped PostgreSQL 11.8 database server.
8月 20 13:41:06 tidb63.com systemd[1]: Starting PostgreSQL 11.8 database server...
8月 20 13:41:06 tidb63.com systemd[1]: Started PostgreSQL 11.8 database server.
8月 20 13:41:30 tidb63.com systemd[1]: Stopping PostgreSQL 11.8 database server...
8月 20 13:41:30 tidb63.com systemd[1]: Stopped PostgreSQL 11.8 database server.
Hint: Some lines were ellipsized, use -l to show in full.
[root@tidb63 system]# 

如果使用systemctl服务器启动了数据库，之后又在postgresql用户下使用pg_ctl关闭实例，再查看服务状态会出现异常。

[root@tidb63 system]# systemctl status pg118.service 
● pg118.service - PostgreSQL 11.8 database server
   Loaded: loaded (/usr/lib/systemd/system/pg118.service; disabled; vendor preset: disabled)
   Active: failed (Result: exit-code) since 四 2020-08-20 13:44:18 CST; 7s ago
  Process: 149196 ExecStop=/usr/local/pgsql/bin/pg_ctl stop -D /home/jm/pg118/pg5432/data -l /tmp/logfile (code=exited, status=1/FAILURE)
  Process: 148969 ExecStart=/usr/local/pgsql/bin/pg_ctl start -D /home/jm/pg118/pg5432/data -l /tmp/logfile (code=exited, status=0/SUCCESS)
 Main PID: 148971 (code=exited, status=0/SUCCESS)

8月 20 13:43:42 tidb63.com systemd[1]: Starting PostgreSQL 11.8 database server...
8月 20 13:43:42 tidb63.com systemd[1]: Started PostgreSQL 11.8 database server.
8月 20 13:44:18 tidb63.com systemd[1]: pg118.service: control process exited, code=exited status=1
8月 20 13:44:18 tidb63.com systemd[1]: Unit pg118.service entered failed state.
8月 20 13:44:18 tidb63.com systemd[1]: pg118.service failed.
[root@tidb63 system]# 

所以，启停pg，全部使用systemctl服务，或者全部使用pg_ctl/postgres/postmaster，不要混用。