Draining, Disabling, or Removing a Node

You might occasionally want to remove one of your back-end nodes from your load-balanced server farm. This could be permanent, or a temporary measure to allow for maintenance or upgrade.

Choose to either "disable" or "drain" the node, such that the Virtual Traffic Manager does not send any new requests, or just remove the node completely from the pool:

To disable, drain, or remove a node from a pool, use the Services > Pools > Edit page. Edit a pool containing the node and change the node status to “Disabled” or “Draining” as required. To remove the node, tick the adjacent Delete checkbox. To save your changes, click Update.

To simplify the processes of disabling, draining, reactivating, or removing nodes across a range of your services, the Virtual Traffic Manager provides a series of wizards. To access the wizards, use the Wizards menu in the top tool bar:

You specify a node to drain/disable (depending on the wizard chosen), and choose whether to apply this for all services or just those you specify. You can restore the node to active status later using the Reactivate a node wizard. To remove a node completely from one or all of your services, use the Remove a node wizard.

Consider disabling a node if you plan to take it out of service temporarily. Existing connections to the node are handled according to the settings discussed in Altering the Behavior of Existing Connections when Disabling or Removing a Node. If the node stops working (for example, because you shut down the server), the Virtual Traffic Manager does not report an error. The advantage of disabling a node rather than removing it from the configuration is that a disabled node can easily be re-instated when it is ready to be used.

Consider draining a node if you are concerned about existing sessions, but bear in mind that if the node stops working, the Virtual Traffic Manager reports an error. If the Virtual Traffic Manager receives a request and session persistence requires that the node is used, the Virtual Traffic Manager continues to use it. If you plan to shut the node down, you should drain it first, waiting until all sessions have completed, then disable it.

To find out whether the node is still handling connections, click Activity > Draining Nodes. This page shows the number of connections the node is still handling, and the time since the last connection. For more details, see Draining Connections. When the node’s existing connections have expired, you can disable it, or use the Remove a Node wizard to remove it cleanly from your cluster.

If you plan to retire one or more server nodes from the pool permanently, and have no requirement to retain any corresponding configuration, delete the nodes from the pool. Existing connections to the node are handled according to the settings discussed in Altering the Behavior of Existing Connections when Disabling or Removing a Node.

If you attempt to remove all nodes from the pool, the Admin UI issues a warning that no new traffic can be received by the pool, and requires explicit consent before this action is completed. To override the warning, tick the confirmation checkbox adjacent to the Update button and try again.

The behavior of existing connections to nodes that you either disable or remove is dependent on the value of node_delete_behavior (found in Services > Pools > Edit > Protocol Settings). This setting has two options: