如何避免在控制台上打印来自 syslog 的广播消息

Question

我写了一个小代码，当无法连接到 postgres 数据库时，使用 C Api 将消息发送到系统日志。

int main ( int argc, char **argv )
{
        PGconn *psql;
        PGresult *res;
        int flag = 0;

        openlog ( "postgres", LOG_NDELAY, LOG_SYSLOG );

        psql = PQconnectdb("hostaddr = '127.0.0.0' port = '5432' dbname = 'RtpDb' user = 'rtp_user_99' password = 'rtp_user' connect_timeout = '10'");
        if ( PQstatus(psql) != CONNECTION_OK )
        {
           //Send an event to syslog for DB Connection Failure
           syslog (LOG_EMERG, "%s", PQerrorMessage(psql) )
        }
       closelog ();
       PQclear(res);
       PQfinish(psql);
}

当与 postgres 数据库的连接失败时，即使未在 openlog 中启用选项 LOG_CONS，也会将消息打印到控制台。

Broadcast message from systemd-journald@blr09 (Tue 2017-01-03 05:24:46 EST):
postgres[40933]: could not connect to server: Network is unreachable
        Is the server running on host "127.0.0.0" and accepting
        TCP/IP connections on port 5432?
Message from syslogd@blr09 at Jan  3 05:24:46 ...
 postgres:could not connect to server: Network is unreachable#012#011Is the server running on host "127.0.0.0" and accepting#012#011TCP/IP connections on port 5432?

能否请您帮我看看如何避免在控制台上打印消息。

Answer 1

根据@alk 提供的提示，我做了更多的研究，找到了如何避免在控制台上打印消息。

Broadcast message from systemd-journald@blr09 (Tue 2017-01-03 05:24:46 EST):
postgres[40933]: could not connect to server: Network is unreachable
        Is the server running on host "127.0.0.0" and accepting
        TCP/IP connections on port 5432?
Message from syslogd@blr09 at Jan  3 05:24:46 ...
 postgres:could not connect to server: Network is unreachable#012#011Is the server running on host "127.0.0.0" and accepting#012#011TCP/IP connections on port 5432?

以上消息分为两部分：

来自 systemd-journald 的广播消息 => 这些消息将在发送紧急消息时由 journalctl 打印在控制台上。要禁用这些消息，我们需要禁用 ForwardToWall 即 ForwardToWall=no in /etc/systemd/journald.conf
来自 syslogd 的消息 => 由于 /etc/rsyslog.conf
中的以下配置行，这些消息由 rsyslog 打印
```
*.emerg                                                 :omusrmsg:*
```

此选择器操作声明 "Emergency messages often go to all users currently online to notify them that something strange is happening with the system. To specify this wall(1)-feature use an ":omusrmsg:*"."注释掉这一行。

执行上述操作后，控制台上未打印消息。由于安全威胁不允许这些操作，我将以 Alert 优先级引发事件。

syslog ( LOG_ALERT, "%s", PQerrorMessage(psql) );

感谢@alk。

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