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    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 Presentation Server to continuously function so that monitoring of your mission-critical systems is continuously available. The 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 as an HA proxy to switch operations between the primary and standby server.

    Presentation Server in HA mode

    The 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 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 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 Presentation Server.  However, it does not manage the failback transfer back to the primary server. You must issue CLI commands to restart the primary server and re-establish its role 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 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 active and standby Presentation Servers

    In the 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.

    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.

    Note

    Do not stop the active server immediately after restarting the standby server. The cache synchronization takes time to complete and is dependent on your environment.

    Limitations of the Presentation Server HA

    • If the host name of the Presentation Server is mapped to the loopback address in the etc/hosts file, HA will not work. Ensure that the hosts file is not updated with the loopback address.
    • If the primary and secondary servers are both disconnected from the network, you must restart both servers, and set one server to the active mode and the other server to standby mode.

    • The primary and secondary server must have identical setups, including the hardware platform, operating system, and post-installation configuration.
    • The Infrastructure Management PATROL Repository is not replicated. Import the repository on both servers. For more information, see Importing the Infrastructure Management repository

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