Disabling Back-end Servers for Maintenance

Avi Vantage provides a way to actively disable back-end servers for maintenance.

When a server is disabled for maintenance, Avi Vantage marks the server Disabled. Existing sessions are terminated immediately or allowed to end gracefully, either with a user-settable maximum timeout or with no timeout. The Graceful Disable Timeout parameter set for a pool governs how servers within the pool are disabled:

  • Disable with immediate effect: All client sessions are immediately terminated. The pool’s Graceful Disable Timeout parameter must be set to 0.
  • Gracefully disable with a finite timeout: No new sessions are sent to the server. Existing sessions are allowed to terminate on their own, up to the specified timeout. Once the timeout is reached, any remaining sessions are immediately terminated. The pool’s Graceful Disable Timeout parameter must be range from 1 to 7200 minutes.
  • Gracefully disable with infinite timeout: No new sessions are sent to the server. All existing sessions are allowed to terminate on their own. The pool’s Graceful Disable Timeout parameter must be set to -1.

When servers are gracefully disabled, until all flows drain, the idle connections, if any, will be deleted immediately.
In-flight connections are closed at the end of a request for request-switched VS and at the end of a client connection for connection-switched virtual service.

When servers are gracefully disabled with a timeout value, the idle connections are closed immediately, while any busy or bound connection will be closed at the end of the timeout. Any exist request will be processed until the end of timeout. Any new requests, no matter it is coming from an exist connection or from a new connection, will be sent to a new server.

Setting a Pool’s Graceful Disable Timeout Parameter

Navigate to Applications > Pools to display a list of pools:

Identify the pool containing the servers whose timeout parameter is to be set, and click on the pencil icon at the right end of that pool’s row. The below editor will be displayed:

Set the Graceful Disable Timeout parameter to 0, -1, or within the range 1 to 7200 minutes, as described above.

Disabling a Server for Maintenance

  1. Navigate to Applications > Pools.
  2. Click on the pool name.
  3. Click on Servers.
  4. Click the checkbox next to the name of each server to disable.
  5. Click on the Disable button.

Note: Avi Vantage also can be configured to use information in the health-check responses from servers to detect when a server is in maintenance mode. For information, click here.