(Optional) Configure the clock source

This topic describes how to configure the Network Time Protocol (NTP) clock source for servers in a cluster. If you are planning to deploy OceanBase Database on a single server, or for personal testing purposes, or if you have already configured NTP clock synchronization, skip this step.

However, if you plan to deploy a distributed OceanBase cluster, it is necessary to ensure time synchronization among all servers in the cluster. Otherwise, the cluster will not be able to start, and the services may encounter exceptions during runtime. The allowed clock deviation in the OceanBase cluster should not exceed 2 seconds. If the deviation exceeds 2 seconds, the cluster may become leaderless. To restore it to normal, you will need to restore clock synchronization and restart the OceanBase cluster.

Prerequisites

You have the root user privileges on all nodes.

Procedure

Perform the following steps to configure the NTP clock source.

1. Run the following command on each server to install NTP:

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

2. Run the following command to check the NTP connection to the server:

   [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) Enable the NTP service.

   If you already have an NTP server, skip this step. This topic uses the target server 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 service:

      [root@test001 ~]# service ntpd restart
      

   3. Run the following command to check whether the NTP service is enabled:

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

   4. Run the following command to enable the NTP service upon startup:

      [root@test001 ~]# chkconfig ntpd on
      

4. Enable the NTP client service.

   Notice

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

   1. Log in to an OBServer node 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 the time with 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 commands return the corresponding results, the NTP service is in effect.