Lanes

A lane is the unit of dispatch control: one destination, one combination of tag values, within your org. Every lane holds its own limits.

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Tags

Tags create lanes. For example, an action tagged {"region": "eu"} and an action tagged {"region": "us"} dispatch through different lanes of the same destination. An action with no tags dispatches through the destination’s default lane. Tags come from:

• The ingress body’s tags field.
• tag.<key> query parameters on ingress.
• A rule with the Assign Tags effect.

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Isolation

Lanes adjust independently. A tenant overwhelming the {"customer": "acme"} lane has no effect on the limits of {"customer": "initech"}. Tag by dimensions that separate failure domains, such as tenant or region.

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Limits

Each lane carries two limits:

• Running limit: the number of deliveries in flight.
• Unsettled limit: the number of deliveries awaiting settlement.

The limits start conservative and follow the destination.

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Caps

A cap pins a lane below what it would otherwise run at. The lanes API accepts a running cap and an unsettled cap, and the engine treats each as a ceiling. A running cap of 0 pauses the lane.

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Cardinality

Tags are for dimensions with a small set of values. An action definition can spread across a maximum of 1000 lanes. Ingress rejects work that would create more with TAG_CARDINALITY_EXCEEDED.

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Reference