(Optional) Configure the clock source

This topic describes how to configure an NTP clock source for multiple machines in a cluster. If you plan to deploy OceanBase Database on a single machine, for personal testing, or if you have already configured NTP clock synchronization, this setting is not required.

If you plan to deploy a distributed OceanBase cluster, you must ensure that the time on all machines within the cluster is synchronized. Otherwise, the cluster cannot be started, and service exceptions may occur during runtime. The allowable clock skew in an OceanBase cluster cannot exceed 2 seconds. When it exceeds 2 seconds, a leaderless state occurs. After restoring clock synchronization, restart the OceanBase cluster to restore normal operation.

Prerequisites

Before configuring the NTP clock source, ensure you have root user privileges on all machines.

Procedure

Follow these steps to configure NTP clock synchronization.

1. On each machine, run the following command to install NTP.

   [root@test002 ~]# yum install ntp ntpdate -y
   

2. Run the following command to check the server's NTP connection.

   [root@test002 ~]# ntpq -4p
   remote refid st t when poll reach delay offset jitter
   ==============================================================================
   *time6.aliyun.co xxx.xxx.xxx.xxx 2 u 712 1024 377 21.951 4.253 4.208
   

3. (Optional) Start the NTP server service.

   If you already have an NTP server, skip this step. This document uses the target machine 10.10.10.1 as the NTP server.

   1. Edit the configuration file.

      Log in to the NTP server as the root user and run the following command to edit the configuration file:

      [root@test001 ~]# vi /etc/ntp.conf
      

      Add the following content to the configuration file:

      server <your_ntp_server_ip>
      

      Save and close the configuration file.

   2. Run the following command to restart the NTP server service:

      [root@test001 ~]# service ntpd restart
      

   3. Run the following command to check whether the NTP server service has started successfully:

      [root@test001 ~]# ps -ef | grep -i ntpd
      

   4. Run the following command to set the NTP service to start automatically at boot:

      [root@test001 ~]# chkconfig ntpd on
      

4. Enable the NTP client service.

   Notice

   After the NTP server service is started, you must wait for 5 minutes before enabling the NTP client service. Otherwise, the system will display the message "no server suitable for synchronization found".

   1. Log in to the OBServer node server as the root user.

   2. Run the following command to stop the NTP service:

      [root@test002 ~]# service ntpd stop
      

   3. Run the following command to synchronize time from the NTP server:

      [root@test002 ~]# ntpdate 10.10.10.1
      

   4. Edit the configuration file.

      Run the following command to open the configuration file:

      [root@test002 ~]# vi /etc/ntp.conf
      

      Add the following content to the configuration file:

      server <your_ntp_server_ip>
      

   5. Run the following command to start the NTP service:

      [root@test002 ~]# /etc/init.d/ntpd start
      

5. Run the following command to verify that the configuration is successful.

   Run the command:

   [root@test002 ~]# ntpstat
   

   The following result is returned:

   synchronised to NTP server (xxx.xxx.xxx.xxx) at stratum 3
   time correct to within 2 ms
   polling server every 64 s
   

   Run the command:

   [root@test002 ~]# timedatectl
   

   The following result is returned:

         Local time: Thu 2021-04-22 11:02:32 CST
     Universal time: Thu 2021-04-22 03:02:32 UTC
           RTC time: Thu 2021-04-22 11:02:32
          Time zone: Asia/Shanghai (CST, +0800)
        NTP enabled: yes
   NTP synchronized: yes
    RTC in local TZ: yes
         DST active: n/a
   

   If the preceding command returns the corresponding result, the NTP service is effective.