案例说明：
通过案例描述KingbaseES V8R3集群异步、同步及全同步强一致性配置，本案例为一主二备的架构。
适用版本：
KingbaseES V8R3
集群架构：
集群复制配置参数说明：
1）sync_flag
[kingbase@node101 bin]$ cat ../etc/HAmodule.conf |grep -i sync_
#1->synchronous cluster,0->asynchronous cluster ,default 1.example:SYNC_FLAG=1
SYNC_FLAG=0
说明：此参数强制配置流复制同异步模式，0为异步模式，1为同步模式。
2）synchronous_standby_names
[kingbase@node101 bin]$ cat ../data/kingbase.conf |grep -i standby_name
##synchronous_standby_names = '' # standby servers that provide sync rep
#synchronous_standby_names='1 (node1, node2)'
说明：此参数用于配置在流复制同步模式下，参与同步复制的备库节点；
例如一主二备集群：'1 (node1,node2,node3)',其中node1是主库，则node2为同步备库，node3为潜在同步备库；
'2 (node1,node2,node3)'，其中node1是主库，则node2为同步备库，node3为同步备库；
synchronous_standby_names = '' ，则node2，node3均为异步备库。
3）synchronous_commit
[kingbase@node101 bin]$ cat ../data/kingbase.conf |grep _commit
#synchronous_commit = on # synchronization level;
说明：用于同步模式下接收到wal日志流的处理方式：
remote_write：备库将wal日志写入到文件系统缓存后，给主库返回commit的ack信息。
on： 备库将wal日志写入到wal日志文件后，给主库返回commit的ack信息。
remote_apply：备库将wal日志写入到wal日志文件并apply后，给主库返回commit的ack信息，
强制主备事务同步。
如下图所示：
一、流复制异步模式配置
1、sync_flag配置
[kingbase@node101 bin]$ cat ../etc/HAmodule.conf |grep -i flag
#1->synchronous cluster,0->asynchronous cluster ,default 1.example:SYNC_FLAG=1
SYNC_FLAG=0
2、集群启动后流复制状态查看
TEST=# select * from sys_stat_replication;
PID | USESYSID | USENAME | APPLICATION_NAME | CLIENT_ADDR | CLIENT_HOSTNAME | CLIENT_PORT | BACKEND_STAR
T | BACKEND_XMIN | STATE | SENT_LOCATION | WRITE_LOCATION | FLUSH_LOCATION | REPLAY_LOCATION | SYNC_PRIOR
ITY | SYNC_STATE
-------+----------+---------+------------------+---------------+-----------------+-------------+---------------------
----------+--------------+-----------+---------------+----------------+----------------+-----------------+-----------
----+------------
31144 | 10 | SYSTEM | node2 | 192.168.1.102 | | 16989 | 2023-05-07 00:55:00.
110856+08 | | streaming | 1/500000D0 | 1/500000D0 | 1/500000D0 | 1/500000D0 |
0 | async
31275 | 10 | SYSTEM | node3 | 192.168.1.103 | | 30046 | 2023-05-07 00:55:03.
014221+08 | | streaming | 1/500000D0 | 1/500000D0 | 1/500000D0 | 1/500000D0 |
0 | async
(2 rows)
# SYNCHRONOUS_STANDBY_NAMES默认配置
[kingbase@node101 data]$ cat kingbase.auto.conf
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
SYNCHRONOUS_STANDBY_NAMES = ''
TEST=# show synchronous_standby_names ;
synchronous_standby_names
---------------------------
(1 row)
如下图所示，两个备库节点流复制均为async模式：
二、流复制同步模式配置
1、sync_flag配置
[kingbase@node101 bin]$ cat ../etc/HAmodule.conf |grep -i flag
#1->synchronous cluster,0->asynchronous cluster ,default 1.example:SYNC_FLAG=1
SYNC_FLAG=1
2、集群启动后流复制状态查看
TEST=# select * from sys_stat_replication;
PID | USESYSID | USENAME | APPLICATION_NAME | CLIENT_ADDR | CLIENT_HOSTNAME | CLIENT_PORT | BACKEND_START
| BACKEND_XMIN | STATE | SENT_LOCATION | WRITE_LOCATION | FLUSH_LOCATION | REPLAY_LOCATION | SYNC_PRIORI
TY | SYNC_STATE
------+----------+---------+------------------+---------------+-----------------+-------------+----------------------
---------+--------------+-----------+---------------+----------------+----------------+-----------------+------------
---+------------
3966 | 10 | SYSTEM | node2 | 192.168.1.102 | | 18965 | 2023-05-07 01:01:12.3
76208+08 | | streaming | 1/510000D0 | 1/510000D0 | 1/510000D0 | 1/510000D0 |
2 | sync
3970 | 10 | SYSTEM | node3 | 192.168.1.103 | | 30106 | 2023-05-07 01:01:14.9
62029+08 | | streaming | 1/510000D0 | 1/510000D0 | 1/510000D0 | 1/510000D0 |
3 | potential
(2 rows)
说明：node2同步模式sync，node3同步模式potential（潜在同步，实为异步）
# SYNCHRONOUS_STANDBY_NAMES默认配置
[kingbase@node101 bin]$ cat ../data/kingbase.auto.conf
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
SYNCHRONOUS_STANDBY_NAMES = '1 (node1, node2, node3)'
TEST=# show synchronous_standby_names ;
synchronous_standby_names
---------------------------
1 (node1, node2, node3)
(1 row)
如下图，默认流复制同步模式配置，其中一个节点为sync，其余为potential：
三、集群流复制全同步模式配置
1、sync_flag配置
[kingbase@node101 bin]$ cat ../etc/HAmodule.conf |grep -i flag
#1->synchronous cluster,0->asynchronous cluster ,default 1.example:SYNC_FLAG=1
SYNC_FLAG=1
2、配置 synchronous_standby_names
TEST=# alter system set synchronous_standby_names='2 (node1, node2, node3)';
ALTER SYSTEM
TEST=# select sys_reload_conf();
SYS_RELOAD_CONF
-----------------
t
(1 row)
TEST=# show synchronous_standby_names ;
synchronous_standby_names
---------------------------
2 (node1, node2, node3)
(1 row)
[kingbase@node101 bin]$ cat ../data/kingbase.auto.conf
# Do not edit this file manually!
# It will be overwritten by ALTER SYSTEM command.
SYNCHRONOUS_STANDBY_NAMES = '2 (node1, node2, node3)'
3、查看流复制同步模式
TEST=# select * from sys_stat_replication;
PID | USESYSID | USENAME | APPLICATION_NAME | CLIENT_ADDR | CLIENT_HOSTNAME | CLIENT_PORT | BACKEND_START
| BACKEND_XMIN | STATE | SENT_LOCATION | WRITE_LOCATION | FLUSH_LOCATION | REPLAY_LOCATION | SYNC_PRIORI
TY | SYNC_STATE
------+----------+---------+------------------+---------------+-----------------+-------------+----------------------
---------+--------------+-----------+---------------+----------------+----------------+-----------------+------------
---+------------
3966 | 10 | SYSTEM | node2 | 192.168.1.102 | | 18965 | 2023-05-07 01:01:12.3
76208+08 | | streaming | 1/510000D0 | 1/510000D0 | 1/510000D0 | 1/510000D0 |
2 | sync
3970 | 10 | SYSTEM | node3 | 192.168.1.103 | | 30106 | 2023-05-07 01:01:14.9
62029+08 | | streaming | 1/510000D0 | 1/510000D0 | 1/510000D0 | 1/510000D0 |
3 | sync
(2 rows)
如下图所示，两个备库节点node2和node3流复制均为sync模式：
4、读写分离配置备库强一致性
[kingbase@node101 log]$ cat ../db/data/kingbase.conf|grep _commit
synchronous_commit = remote_apply # synchronization level;
说明：配置synchronous_commit = remote_apply，主库事务commit，需要等待所有备库
接收到wal日志流并写入到wal日志文件，执行apply完成事务的操作后，向主库返回ack，
主库完成事务的commit。
因此，此时主库及备库查询到的事务的结果是一致的，但是对事务繁忙的业务， 性能
会有很大的影响。
四、总结
KingbaseES V8R3和KingbaseES V8R6集群在流复制同异步模式配置不同，通过以上案例的描述，可以了解到在KingbaseES V8R3集群下流复制模式的详细配置过程。