Introducing a more transparent load balancer in ThinLinc 4.19.0

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With the recently released ThinLinc 4.19.0, we introduced major updates to the load balancer – the component that decides how users are distributed across cluster agents. The new design is simpler and more predictable, and also easier to understand.

My name is Tobias Fahleson, and I’m part of the ThinLinc development team at Cendio. I worked on several aspects of the new load balancer, but I was mainly involved with the rework of the penalty system.

What changed

Historically, ThinLinc has balanced users by tracking used computational resources such as CPU and memory, ranking agents for session assignment. While powerful in theory, it was somewhat complex and difficult to tune.

The new system takes a different path:

  • Even user distribution: By default, users are now balanced evenly across
    agents

  • Agent weights reworked: Configured weights now represent relative
    capacity. For example, two agents with weights 50 and 100 will split
    users in a 1:2 ratio

  • Penalty rework: Rather than accumulating penalty points, agents that
    fail to start sessions are now temporarily moved to the back of the
    eligible agents queue

  • Responsiveness: The load balancer can now make distribution decisions
    confidently during login storms, without relying on load metrics to
    stabilize

  • Drain mode: Agents can be taken out of rotation for new sessions while
    keeping existing ones running, which is useful when preparing for
    maintenance

For administrators, the load balancer now offers transparency and predictability. Maintenance planning becomes easier and cluster management requires less effort overall.

For users, the login experience is more reliable, as even user distributions reduce the chance of overloading and failed session startups. In addition, drain mode helps prevent users from starting new sessions on agents about to go offline – replacing the old workaround of temporarily removing the agent from the cluster.

Try it out!

This update is one of our biggest steps towards simplifying ThinLinc cluster management. Upgrade to version 4.19.0 to try the new load balancer. As always, we welcome your feedback – which feature do you find most useful?

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