TrueSight Presentation Server high availability deployment

High availability (HA) is a redundancy operation that automatically switches to a standby server if the primary server fails or is temporarily shut down for maintenance. HA enables the TrueSight Presentation Server to continuously function so that monitoring of your mission-critical systems is continuously available. The TrueSight Presentation Server supports out-of-the box HA that eliminates the need for third-party software and reduces the manual steps required to deploy. HA utilizes a load balancer software component to switch operations between the primary and standby server.

Presentation Server in HA mode

The TrueSight Presentation Server in HA mode consists of two servers with identical configurations. The first server is referred to as the primary server, and the standby server is referred to as the secondary server.  The primary server always takes on an active role and all the TrueSight Presentation Server processes that are running during this time. When the primary server is down or in case of a failover, the secondary server takes on an active role. Only one TrueSight Presentation Server can be active at a time. In case of a failover due to an event that triggers a server shutdown, the secondary server takes over the active role, and all of the processes change from standby mode to operation mode on the secondary server.

The detection and management of a failover is built in to the TrueSight Presentation Server.  However, it does not manage the failback transfer back to the primary server. See Transferring the service between the secondary server and primary server to re-establish the primary server as the active server.

HA architecture

the TrueSight Operations Management HA deployment comprises the following systems:

• Primary server
• Secondary server
• Load balancer 

A load balancer is a software component that routes the client requests to the active server. In the context of the TrueSight Presentation Server system, the load balancer is more of a proxy server that accepts client requests and directs these requests to the active server. The load balancer resides on a separate computer and redirects requests to the active server.

Why is a load balancer required?

In a successful HA deployment, the secondary server must take over when the primary server is not working, or the primary server is ready to take over a load balancer is required to direct the client requests to the active server.

A load balancer:

• Gives a unified contact point to access the Presentation Server
• Enables to detect the active node, primary or secondary server, automatically in an HA deployment.

HA deployment options

There are two ways to deploy the TrueSight Presentation Server in HA mode:

• Deploying in HA mode during the installation process
• Deploying in HA mode post-installation

Deploying TrueSight Presentation Server in HA mode during installation

You can choose to deploy the TrueSight Presentation Server in HA mode during installation by selecting the Enabled option, If you choose to enable HA, you must specify which system is the primary server and which system is the secondary server. For information about deploying in HA mode during installation, see Performing the Presentation Server installation.

Deploying TrueSight Presentation Server in HA mode post installation

You can choose to deploy the TrueSight Presentation Server in HA Primary mode or HA Secondary mode post installation.

Navigate to the <Presentation Server installation directory>\truesightpserver\bin directory, open a CLI command prompt, and run the following commands:

1. Run the tssh server stop command on the primary and the secondary server.
2. Run the tssh process start database command on the primary server. 
3. Run the tssh ha configure master command on the primary server.
   Provide the primary and the secondary server details in the CLI which will be used to generate the configuration information in the ha-shared.conf file. Copy the ha-shared.conf file to the secondary server.
4. Run the tssh process stop database on the primary server.
5. Run the tssh server start command on the primary server.
6. Run the tssh ha configure standby command on the secondary server. 
   Type the path to the ha-shared.conf file.
7. Run the command tssh ha copysnapshot on the secondary server.
8. Run the tssh server start command on the secondary server.

Transferring the service between the secondary server and primary server

In the TrueSight Presentation Server HA mode, the secondary server becomes the active server if the primary server stops operating, due to an event that triggers a server shutdown. Once the primary server is up and running, it does not become the active server by default. The primary server is still in a standby mode. The service can be transferred back to the primary server, or the primary server can remain in standby mode.

To transfer service back to the primary server, perform the following steps:

1. Run the tssh server stop CLI command on the secondary server. This command stops the secondary server and re-establishes the primary server as the active server.
2. Run the tssh ha status CLI command on the primary server and ensure that it is the active server.
3. Run the tssh server start CLI command on the secondary server. This command starts the secondary server.
4. Run the tssh ha status CLI command on the secondary server and ensure that it is the standby server.

During a failover, if you are accessing the TrueSight console using a load balancer, you might view error messages such as The Server is unable to respond. Any operation using the TrueSight console might fail. This is a temporary condition and normalcy is restored when the active node becomes fully operational.

Limitations of the TrueSight Presentation Server HA