Admission

Admission control determines when an accepted action may leave Arklow. It evaluates the action’s lane, the destination’s recent behavior, and any shared capacity behind it. Decisions made by admission control are done so quickly. For performance questions, our SDK documentation describes what to expect.

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What does admission weigh?

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Running and unsettled capacity

In addition, Admission takes great care to measure two important observables: A destination that acknowledges work in its response may use running capacity only briefly. A destination that accepts work for later settlement continues to occupy unsettled capacity after the response. For example, work given to one of your SDK listeners, will be counted as unsettled until the work is marked completed, either by you, or in the case of Defer, if you stop replying. Both reservations apply. A destination may have room to begin another delivery while carrying too much unfinished work, or it may have unfinished-work room while its delivery contacts are already busy.

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Lanes

Lanes are described in detail here.

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Waiting and recovery

An action awaiting admission enters dispatch_wait before any delivery attempt. Its action timeout continues to apply while it waits. The action becomes eligible again as deliveries finish or settle, rate guidance clears, pool allocation changes, or a temporary control expires. Healthy outcomes and available capacity allow waiting work to resume. Admission remains active while a scale target adds capacity.

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Temporary caps and pauses

Lane advice can temporarily cap running or unsettled admission during an incident or maintenance window. A running cap of 0 pauses new admission. Advice can carry an expiry, after which the lane returns to its remaining controls.

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Write control

While the admission member of Write Control is off, admission decisions are recorded and every release is immediate. While it is on, the decisions on this page apply.