1. 问题现象

达梦主从集群监视器连接均存在连接异常的情况。 目前均需要等待30秒才能返回结果（10:34:16-10:34:46），正常应该是秒回，如下：

[dave@www.cndba.cn dmdata]$ dmmonitor dmmonitor_normal.ini
Mon Oct 10 10:34:16 CST 2022
[monitor]         2022-10-10 10:34:16: DMMONITOR[4.0] V8
[monitor]         2022-10-10 10:34:46: DMMONITOR[4.0] IS READY.

[monitor]         2022-10-10 10:34:46: Received message from(IDP1)
                  WTIME                WSTATUS        INST_OK   INAME            ISTATUS     IMODE     RSTAT    N_OPEN   FLSN            CLSN            
                  2022-10-10 10:34:46  OPEN           OK        IDP1             OPEN        PRIMARY   VALID    8        506850          506851          

[monitor]         2022-10-10 10:34:46: Received message from(IDP2)
                  WTIME                WSTATUS        INST_OK   INAME            ISTATUS     IMODE     RSTAT    N_OPEN   FLSN            CLSN            
                  2022-10-10 10:34:46  OPEN           OK        IDP2             OPEN        STANDBY   VALID    8        506849          506849

2. 解决方法

是DNS导致了getaddrinfo函数异常。 http://www.cndba.cn/dave/article/108674http://www.cndba.cn/dave/article/108674

经过测试，以下2种方法都可以解决连接异常的问题：

方法1：注释掉dns 配置文件中的所有内容：

[dave@www.cndba.cn ~]# cat /etc/resolv.conf
# Generated by NetworkManager
#search openstacklocal
#nameserver 192.125.0.112
#nameserver 192.125.0.113
#options single-request-reopen
[dave@www.cndba.cn ~]#

方法2： 将集群涉及到所有IP地址都配置到/etc/hosts文件中：http://www.cndba.cn/dave/article/108674

[dave@www.cndba.cn ~]# cat /etc/hosts
::1    localhost    localhost.localdomain    localhost6    localhost6.localdomain6

127.0.0.1    localhost    localhost.localdomain    localhost4    localhost4.localdomain4

192.168.168.194 dave01
192.168.168.221 dave02
192.168.168.28 dave03

虽然目前数据库并没有使用的DNS，但后期其他软件可能会使用到。所以采用第二种方法来解决问题，添加之后，监视器秒回：http://www.cndba.cn/dave/article/108674

[dave@www.cndba.cn dmdata]$ dmmonitor dmmonitor_normal.ini
[monitor]         2022-10-10 11:05:39: DMMONITOR[4.0] V8
[monitor]         2022-10-10 11:05:39: DMMONITOR[4.0] IS READY.

[monitor]         2022-10-10 11:05:40: Received message from(IDP1)
                  WTIME                WSTATUS        INST_OK   INAME            ISTATUS     IMODE     RSTAT    N_OPEN   FLSN            CLSN            
                  2022-10-10 11:05:39  OPEN           OK        IDP1             OPEN        PRIMARY   VALID    8        507468          507468          

[monitor]         2022-10-10 11:05:40: Received message from(IDP2)
                  WTIME                WSTATUS        INST_OK   INAME            ISTATUS     IMODE     RSTAT    N_OPEN   FLSN            CLSN            
                  2022-10-10 11:05:39  OPEN           OK        IDP2             OPEN        STANDBY   VALID    8        507467          507467

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