本篇内容介绍了“PostgreSQL HA环境分析”的有关知识，在实际案例的操作过程中，不少人都会遇到这样的困境，接下来就让小编带领大家学习一下如何处理这些情况吧！希望大家仔细阅读，能够学有所成！
基于streaming replication搭建的PostgreSQL HA环境,Old Standby节点升级为New Master节点后,时间线会切换为新的时间线,比如从n变为n + 1.而Old Master节点的时间线仍然为原来的时间线,比如仍为n,通过使用pg_rewind工具,可使原来其实”完好”的Old Master成为New Standby节点.
图解
如下图所示:
在执行主备切换后,New Master节点的时间线切换为n + 1,通过pg_rewind可使Old Master在分叉点开始与New Master同步,成为New Standby节点.
实测
New Master
切换后为New Master后,执行以下SQL:
计算
安全
数据库
网络和加速
企业服务
testdb=# create table t_new(id int,flag varchar(40));
CREATE TABLE
testdb=# insert into t_new select c,'flag'||c from generate_series(1,1000000) as c;
INSERT 0 1000000
testdb=#Old Master
执行pg_rewind前,重启主库,执行以下SQL
testdb=# create table t_fork(id int,flag varchar(40));
CREATE TABLE
testdb=# insert into t_fork select c,'flag'||c from generate_series(1,1000000) as c;
INSERT 0 1000000
testdb=#执行pg_rewind
[xdb@localhost testdb]$ cp /data/archivelog/* ./pg_wal
[xdb@localhost testdb]$ pg_rewind --target-pgdata=$PGDATA --source-server="host=192.168.26.25 port=5432 dbname=testdb" --progress
connected to server
servers diverged at WAL location 0/B41F12B8 on timeline 23
rewinding from last common checkpoint at 0/AFCF99E0 on timeline 23
reading source file list
reading target file list
reading WAL in target
need to copy 360 MB (total source directory size is 501 MB)
369312/369312 kB (100%) copied
creating backup label and updating control file
syncing target data directory
Done!配置recovery.conf文件
[xdb@localhost testdb]$ mv recovery.done recovery.conf
[xdb@localhost testdb]$ vim recovery.conf
[xdb@localhost testdb]$ cat recovery.conf
standby_mode = 'on'
primary_conninfo = 'user=replicator password=replicator host=192.168.26.26 port=5432 sslmode=prefer sslcompression=0 krbsrvname=postgres target_session_attrs=any'
restore_command = 'cp /data/archivelog/%f %p'重启数据库
[xdb@localhost testdb]$ pg_ctl start
waiting for server to start....2019-03-28 12:39:31.918 CST [1961] LOG: listening on IPv4 address "0.0.0.0", port 5432
2019-03-28 12:39:31.918 CST [1961] LOG: listening on IPv6 address "::", port 5432
2019-03-28 12:39:31.920 CST [1961] LOG: listening on Unix socket "/tmp/.s.PGSQL.5432"
2019-03-28 12:39:31.970 CST [1961] LOG: redirecting log output to logging collector process
2019-03-28 12:39:31.970 CST [1961] HINT: Future log output will appear in directory "pg_log".
... done
server started与New Master数据同步了,而在原TL上的t_fork数据表消失了.
testdb=# select count(*) from t_new;
count
---------
1000000
(1 row)
testdb=# select count(*) from t_old;
count
---------
1000000
(1 row)
testdb=# select count(*) from t_fork;
ERROR: relation "t_fork" does not exist
LINE 1: select count(*) from t_fork;
^
testdb=#“PostgreSQL HA环境分析”的内容就介绍到这里了，感谢大家的阅读。如果想了解更多行业相关的知识可以关注亿速云网站，小编将为大家输出更多高质量的实用文章！
亿速云「云服务器」，即开即用、新一代英特尔至强铂金CPU、三副本存储NVMe SSD云盘，价格低至29元/月。点击查看>>
免责声明：本站发布的内容（图片、视频和文字）以原创、转载和分享为主，文章观点不代表本网站立场，如果涉及侵权请联系站长邮箱：is@yisu.com进行举报，并提供相关证据，一经查实，将立刻删除涉嫌侵权内容。
原文链接：http://blog.itpub.net/6906/viewspace-2639592/
