Virtual IP address failover for Applications Manager

Overview

Failover is an alternative monitoring mechanism that facilitates switching to a secondary/backup server when the primary server becomes unavailable. Configuring Applications Manager’s dual server failover system ensures constant availability so you can monitor all your business-critical applications without any interruptions. Learn more.

A Virtual IP address for failover is a shared IP address used by primary and secondary servers that belong to the same subnet. The virtual IP points to the secondary/backup server in case the primary server goes down. This way, the user can access both the primary and secondary/backup servers using a single IP address.

How it works

• If the primary Applications Manager server is up and working, a Virtual IP address will be assigned to it.
• In case the primary Applications Manager server goes down, the Virtual IP address will be dissociated from it and will instead be assigned to the secondary/backup server which will then take over the primary server’s function.
• This way the end user will always be able to access the application via a single IP address.

Prerequisites

The following are the prerequisites that need to be implemented before configuring the VIP Failover mode:

• Virtual IP address: A Virtual IP address is a common IP address that is shared by both the primary and the secondary server on the same subnet. When one server goes down, the Virtual IP address points to the other server.
• Virtual Host Name (optional): The hostname for the Virtual IP address. It should resolve to the corresponding Virtual IP address and vice versa.
• Hardware and software requirements:
  • The same edition of Applications Manager must be installed on both servers.
  • Both servers must have the same port and protocol. (http/https)
  • Both primary and secondary APM installed machines must be under the same time zone. (Not mandatory)
  • Both primary and secondary APM installed machines must have the same hardware configurations. (Not mandatory)
• Network requirements:
  • Both the primary and the secondary servers must have a static IP address.
  • The Virtual IP must be static and in IPv4 format.
  • Both servers must be able to determine each other's IP addresses and hostnames.
  • The IP and Virtual IP addresses of both servers must belong to the same subnet.
  • Both servers must have high connectivity and bandwidth.
• Prerequisites for Linux build: In Linux, the addition of a Virtual IP Address requires SUDO permission. Follow the steps given below in both the primary and secondary servers.
  1. Edit the sudo configuration file using the command:

     sudo visudo

  2. Add the following line to the end of the file:

     <USERNAME> ALL= NOPASSWD:/usr/sbin/ip

     Here, <USERNAME> refers to the username of the machine.
     For example:
     

  Note: The above steps are not required if the setup has been installed with ROOT user privilege. Ensure to implement the prerequisites correctly, or else the setup might not start/stop properly.

Configure Virtual IP address for Failover

1. To configure the Virtual IP address for Failover in Applications Manager go to Settings → Server Settings → High Availability Settings.
2. Fill in the following details to associate Virtual IP for the Failover option:
   • Virtual IP address: The IP address that does not belong to a physical network interface. The IP and the Virtual IP addresses of both servers must belong to the same subnet.
   • Virtual Hostname (optional): The hostname of the Virtual IP address. The hostname must recognize the corresponding Virtual IP address and vice versa.
   • Retry Count: The number of failed association attempts that must be made before initiating the failover mode.
   • Retry Interval in secs: Time interval required to reattempt connecting to the associated Virtual IP address.
3. Next, follow the steps mentioned below for the changes to take effect:
   • Stop the backup / secondary server first (if running). Next, stop the primary server.
   • Now start the primary server. Once it's up and running, proceed to start the secondary server.
   • Once the product has been started successfully it can be accessed via https://<vip>:<port>.