案例说明：
在KingbaseES V8R3集群在连接kingbasecluster服务（9999端口）时，出现“message length (8) in slot 1 does not match with slot 0(12)”故障，通过复现，获取故障发生的原因。故障信息如下图所示：
适用版本：
KingbaseES V8R3
集群状态：
一、配置备库sys_hba.conf文件
1、主库sys_hba.conf文件
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all md5
# IPv4 local connections:
host all all 127.0.0.1/32 md5
host all all 0.0.0.0/0 md5
# IPv6 local connections:
host all all ::1/128 md5
host all all ::0/0 md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local replication SYSTEM md5
host replication SYSTEM 127.0.0.1/32 md5
#host replication SYSTEM ::1/128 md5
host all SYSTEM 192.168.1.101/24 md5
host replication SYSTEM 192.168.1.101/24 md5
host all SYSTEM 192.168.1.102/24 md5
host replication SYSTEM 192.168.1.102/24 md5
2、备库sys_hba.conf文件
如下图所示，当备库和主库的配置不同时：
二、连接备库9999端口服务
1、备库连接9999端口服务
[kingbase@node102 bin]$ ./sys_ctl reload -D ../data
server signaled
[kingbase@node102 bin]$ ./ksql -U SYSTEM -W 123456 TEST -p 9999
ksql: ERROR: unable to read message length
DETAIL: message length (8) in slot 1 does not match with slot 0(12)
在备库cluster.log日志中显示：
2、主库连接9999端口服务
[kingbase@node101 bin]$ ./ksql -U SYSTEM -W 123456 TEST -p 9999
ksql (V008R003C002B0370)
Type "help" for help.
TEST=#
---如上所示，主库连接9999端口正常。
---如上所示，备库在连接9999端口服务时，出现“message length (8) in slot 1 does not match with slot 0(12)“错误，主库可以正常连接。
三、配置主库sys_hba.conf文件
1、备库sys_hba.conf文件
# TYPE DATABASE USER ADDRESS METHOD
# "local" is for Unix domain socket connections only
local all all md5
# IPv4 local connections:
host all all 127.0.0.1/32 md5
host all all 0.0.0.0/0 md5
# IPv6 local connections:
host all all ::1/128 md5
host all all ::0/0 md5
# Allow replication connections from localhost, by a user with the
# replication privilege.
#local replication SYSTEM md5
host replication SYSTEM 127.0.0.1/32 md5
#host replication SYSTEM ::1/128 md5
host all SYSTEM 192.168.1.101/24 md5
host replication SYSTEM 192.168.1.101/24 md5
host all SYSTEM 192.168.1.102/24 md5
host replication SYSTEM 192.168.1.102/24 md5
2、主库sys_hba.conf文件
如下图所示，配置主库与备库sys_hba.conf：
四、连接主备库的9999（kingbasecluster）服务
1、备库连接9999
[kingbase@node102 bin]$ ./ksql -U SYSTEM -W 123456 TEST -p 9999
ksql: ERROR: unable to read message length
DETAIL: message length (12) in slot 1 does not match with slot 0(8)
2、主库连接9999
[kingbase@node101 bin]$ ./ksql -U SYSTEM -W 123456 TEST -p 9999
ksql: ERROR: unable to read message length
DETAIL: message length (12) in slot 1 does not match with slot 0(8)
---如上所示，主备库连接9999端口都出现了”message length (12) in slot 1 does not match with slot 0(8)“故障信息。
五、总结
当主备库的sys_hba.conf中，对用户连接集群的认证方式不同时，将会出现”message length (12) in slot 1 does not match with slot 0(8)“的故障，在生产环境中注意集群配置文件配置，主备库配置要一致。