Module keepalive 

Keeping a VM awake from outside while work runs inside it.

The platform measures idleness by inbound requests through the endpoint proxy. Work inside the guest does not count: measured 2026-09-23 in us-east-1, a CPU-busy exec was suspended between 60 and 70 seconds after the last inbound request under a 60-second maxIdleDurationSeconds. Requests from inside the guest arrive over loopback and never reach the meter. So the only keepalive is a caller outside the VM that keeps sending requests, and KeepAwake is that caller: an unauthenticated GET /v1/health every interval, optionally ending once the daemon stops reporting busy.

Why the interval is capped at half the idle window

One missed poll must not suspend the VM. With the interval at most half the window, a single failed or slow poll still leaves a second one inside the window. When the caller does not know the VM’s window, the cap assumes the smallest window the platform accepts (MIN_IDLE_DURATION_SEC), which is the only assumption that cannot be too generous.

The probe is the caller’s

KeepAwake::run owns the policy (cadence, busy, deadline, error tolerance, stop) and takes the poll as a closure. super::Session::keep_awake passes its own health call. A binding holding a sandbox-owned session passes one that first checks, under the sandbox’s lock, that the VM is still running and answers None when it is not: a health poll against a VM the caller just suspended would auto-resume it, which is the opposite of what a suspend asked for.

Structs

KeepAwake

A keepalive’s policy. Build with KeepAwake::new, check with KeepAwake::validate.

KeepAwakeReport

What a finished keepalive did.

KeepAwakeTask

A keepalive running as a background task. Dropping it stops the task.

Enums

KeepAwakeEnd

Why a keepalive ended without an error.

Constants

DEFAULT_KEEP_AWAKE_INTERVAL

The default cadence when the caller names none: a third of the window, at most this.

DEFAULT_TOLERATED_ERRORS

Consecutive retryable poll failures tolerated before the keepalive gives up.

Type Aliases

RunningGate

Whether the VM behind a keepalive is still one it may poll. See the module docs.