Andras Bacsai
2.1 KiB
Supervisor & Balancing Configuration
Where to Find It
Search with search-docs before writing any supervisor config, as option names and defaults change between Horizon versions:
"horizon supervisor configuration"for the full options list"horizon balancing strategies"for auto, simple, and false modes"horizon autoscaling workers"for autoScalingStrategy details"horizon environment configuration"for the defaults and environments merge
What to Watch For
The environments array merges into defaults rather than replacing it
The defaults array defines the complete base supervisor config. The environments array patches it per environment, overriding only the keys listed. There is no need to repeat every key in each environment block. A common pattern is to define connection, queue, balance, autoScalingStrategy, tries, and timeout in defaults, then override only maxProcesses, balanceMaxShift, and balanceCooldown in production.
Use separate named supervisors to enforce queue priority
Horizon does not enforce queue order when using balance: auto on a single supervisor. The queue array order is ignored for load balancing. To process notifications before default, use two separately named supervisors: one for the high-priority queue with a higher maxProcesses, and one for the low-priority queue with a lower cap. The docs include an explicit note about this.
Use balance: false to keep a fixed number of workers on a dedicated queue
Auto-balancing suits variable load, but if a queue should always have exactly N workers such as a video-processing queue limited to 2, set balance: false and maxProcesses: 2. Auto-balancing would scale it up during bursts, which may be undesirable.
Set balanceCooldown to prevent rapid worker scaling under bursty load
When using balance: auto, the supervisor can scale up and down rapidly under bursty load. Set balanceCooldown to the number of seconds between scaling decisions, typically 3 to 5, to smooth this out. balanceMaxShift limits how many processes are added or removed per cycle.