Back-end load balancing and failover

Back-end load balancing is used to distribute requests for the same application over several back-end hosts in a predefined way. This can also be used to design back-end failover scenarios, or account for performance differences between back-end servers

Each back-end host can be assigned a weight value, or it can be marked as a spare. spare back-end hosts do not carry a weight value. Airlock Gateway automatically assigns a weight to a back-end host when its spare checkbox is un-ticked.

The weights assigned to all non-spare and enabled back-end hosts of a back-end group are used to calculate which percentage of the traffic each back-end host should receive. The calculated percentage is used as a starting point when distributing load over a back-end group's back-end hosts. Depending on the operational situation, these values can change dynamically.

Note that individual sessions - not requests - are distributed over the back-end hosts according to the set weights (and calculated percentages). Once a specific user's session is tied to a specific back-end host, it will be served by that particular back-end host for the whole lifetime of the session, or until that back-end host becomes unresponsive.