In the previous article, we completed the initial configuration of the GBase 8s HAC cluster. This article will focus on configuring trust relationships between the primary and secondary nodes and how to set up and verify the HAC cluster status.

1. Configuring Trust

Trust is the foundation for communication between cluster nodes. We can achieve this by configuring the .rhosts file or using the REMOTE_SERVER_CFG parameter. Choose the appropriate trust configuration method based on your enterprise's security requirements.

Configuring Trust with the .rhosts File

The .rhosts file in the user's home directory contains trusted {host ~ user} relationships, granting trust to a specific account on a specific host. Simply put, .rhosts is about the trust of the same user across different hosts, only trusting a specific user on a trusted host. This method is suitable for environments with low security requirements for the operating system, where trust needs to be specified at the user level. The gbasedbt user can modify the .rhosts file to configure trust.

Configuration Steps:

1. First, modify the /etc/hosts file. Execute the following as the root user on both the primary and secondary nodes: vi /etc/hosts. Add the IP addresses and hostnames of the primary and secondary nodes. The configuration should be the same on both servers.
   

   [root@localhost opt]# cat /etc/hosts
   127.0.0.1   localhost localhost.localdomain localhost4 localhost4.localdomain4
   ::1         localhost localhost.localdomain localhost6 localhost6.localdomain6
   192.168.16.128    prim
   192.168.16.129    hac
   

2. After modifying the /etc/hosts file, create a .rhosts file in the gbasedbt user's home directory. Add the hostnames and the trusted user gbasedbt for both nodes in the file.
   

   [gbasedbt@hac ~]$ cat .rhosts 
   prim gbasedbt
   hac  gbasedbt
   

3. Finally, configure the correct sqlhosts file to complete the trust setup. The configuration of the sqlhosts file was covered in the previous article. This completes the trust configuration.

Configuring Trust with the REMOTE_SERVER_CFG Parameter

The REMOTE_SERVER_CFG parameter specifies a file that lists trusted remote hostnames or IP addresses. This file must be located in the $GBASEDBTDIR/etc directory. If this parameter is set, the /etc/hosts.equiv file will not be used. This method is suitable for environments with high-security requirements for the operating system, where the operating system checks for trust files like hosts.equiv and prohibits trust at the OS level. In this case, trust can be configured using the REMOTE_SERVER_CFG parameter within the database.

Configuration Steps:

1. First, create a hosts.trust file in the etc directory of the database installation directory. Do this on both the primary and secondary nodes.
   

   [gbasedbt@hac ~]$ cd $GBASEDBTDIR/etc
   [gbasedbt@hac ~]$ vi hosts.trust
   [gbasedbt@hac ~]$ cat hosts.trust
   + gbasedbt 
   

2. Next, modify the REMOTE_SERVER_CFG parameter. Use gadmin -wf to dynamically modify the parameter or modify the onconfig file and restart the database. The default value of REMOTE_SERVER_CFG is empty; change it to hosts.trust. Do this on both the primary and secondary nodes.
   

   [gbasedbt@hac ~]$ gstat -g cfg | grep REMOTE_SERVER_CFG
   Your evaluation license will expire on 2025-07-06 00:00:00
   REMOTE_SERVER_CFG         hosts.trust   
   S6_USE_REMOTE_SERVER_CFG  0
   

3. Finally, configure the correct sqlhosts file to complete the trust setup. The configuration of the sqlhosts file was covered in the previous article. This completes the trust configuration.

2. Setting Up the HAC Cluster

After completing the preparation work, we can set up the cluster relationship.

1. First, set the primary node. In the command, HAC is the name of the secondary node instance. Afterward, check the cluster status. You will find that HAC is in a Disconnected state.
   

   [gbasedbt@prim ~]$ onmode -d primary hac
   Your evaluation license will expire on 2025-07-06 00:00:00
   [gbasedbt@prim ~]$ gstat -g cluster
   Your evaluation license will expire on 2025-07-06 00:00:00
   On-Line (Prim) -- Up 00:04:57 -- 674664 Kbytes
   Primary Server:prim
   Current Log Page:7,4078
   Index page logging status: Enabled
   Index page logging was enabled at: 2024/07/07 14:28:24
   
   Server ACKed Log    Applied Log  Supports     Status
         (log, page)  (log, page)  Updates
   hac    0,0          0,0          No           ASYNC(HDR),Disconnected,Off
   

2. Next, perform data recovery. Ensure that the secondary node is in a shutdown state before executing the following command. Execute the command on the primary node:
   

   [gbasedbt@prim gbase_dbs]$ ontape-s -L 0 -t STDIO | ssh 192.168.16.129 "source /home/gbasedbt/profile.hac && ontape-p -t STDIO"
   Your evaluation license will expire on 2025-07-06 00:00:00
   The authenticity of host '192.168.16.129 (192.168.16.129)' can't be established.
   ECDSA key fingerprint is SHA256:XH0PY7Yz01qxcIYvvhfH/9++RyQDPiKfjTntyQ1CpSw.
   ECDSA key fingerprint is MD5:5d:aa:64:0e:13:1f:f0:26:f8:34:a2:49:f2:bf:8c:e5.
   Are you sure you want to continue connecting (yes/no)? yes
   Warning: Permanently added '192.168.16.129' (ECDSA) to the list of known hosts.
   gbasedbt@192.168.16.129's password: 
   Your evaluation license will expire on 2025-07-06 00:00:00
   Your evaluation license will expire on 2025-07-06 00:00:00
   

3. After executing this command on the primary node, check the status of the secondary node. The secondary node will now be in Fast Recovery state.
   

   [gbasedbt@hac gbase_dbs]$ gstat -
   Your evaluation license will expire on 2025-07-06 00:00:00
   Fast Recovery -- Up 00:00:50 -- 597864 Kbytes
   

4. Now, set the secondary node. Execute the following commands on the secondary node. After execution, check the status of the secondary node. The secondary node status will first change to Fast Recovery (Sec) and then to Read-Only (Sec). At this point, check the cluster status. The hac node will be in Connected state. This completes the HAC cluster setup.
   

   [gbasedbt@hac gbase_dbs]$ gadmin -d secondary prim
   Your evaluation license will expire on 2025-07-06 00:00:00
   [gbasedbt@hac gbase_dbs]$ gstat -
   Your evaluation license will expire on 2025-07-06 00:00:00
   Fast Recovery (Sec) -- Up 00:01:40 -- 1135464 Kbytes
   [gbasedbt@hac gbase_dbs]$ gstat -
   Your evaluation license will expire on 2025-07-06 00:00:00
   Read-Only (Sec) -- Up 00:02:12 -- 1135464 Kbytes
   [gbasedbt@hac ~]$ gstat -g cluster
   Your evaluation license will expire on 2025-07-06 00:00:00
   Read-Only (Sec) -- Up 03:23:00 -- 1135464 Kbytes
   Primary Server:prim
   Index page logging status: Enabled
   Index page logging was enabled at: 2024/07/07 14:28:24
   
   Server ACKed Log    Supports     Status
         (log, page)  Updates
   hac    7,4111       No           ASYNC(HDR),Connected,On
   

With this article and the previous one, we have covered the entire process of setting up and deploying the GBase 8s HAC cluster. Building a high-availability cluster is crucial for ensuring the stable operation of enterprise databases. I hope this article helps you better understand and apply the HAC features of GBase 8s.