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substrate/docs
Dmitry Berkovich 3a2d0c1d86 Support suspending a PAUSED actor without waking it (#816)
Part of #791 — the last planned piece of the [implementation
plan](https://github.com/agent-substrate/substrate/issues/791#issuecomment-5226674097)
(after #810, #812, #813). #791 stays open until #817 (gVisor
Full-capture → Data-commit conversion, blocked on #790) is done; this PR
covers micro-VM fully and gVisor for scope-matched suspends. Also part
of the actor state machine (#119) and a prerequisite for system upgrade
flows (#473).

`SuspendActor` now accepts a PAUSED actor: instead of checkpointing a
running workload, ateapi dials the atelet on the node holding the pause
snapshot and has it upload the node-local files to object storage, then
finalizes as usual — durable `ActorSnapshot`, `SUSPENDED` status, node
pinning cleared.

Two commits, reviewable independently:

## Commit 1 — atelet: `UploadPausedCheckpoint` RPC (dead code until
commit 2)

- New `AteomHerder` RPC: a pure disk→object-storage copy driven by the
snapshot's self-describing manifest — no ateom involved (the sandbox is
gone).
- **Scope conversion** dispatches per sandbox class
(`narrowFullCaptureToData`): a micro-VM FULL capture narrows to a DATA
upload by carving out `durable-dir.tar` (constant hoisted to
`ateompath`, shared with ateom-microvm); gVisor returns `Unimplemented`
until split checkpoints land (#790); DATA can never widen to FULL; a
scope-less manifest (older atelet) is rejected rather than guessed at.
- **Idempotent retry**: local files gone + remote manifest present ⇒ a
previous invocation committed, succeed; gone on both sides ⇒
unrecoverable (`LOCAL_SNAPSHOT_GONE`, crashes the actor). Upload
failures stay plain retryable errors; the manifest uploads last as the
commit marker, never in parallel.
- The golden atespace is rejected at validation (fully on the
`field.ErrorList` framework): golden actors are never paused.

## Commit 2 — control plane: enable suspend from PAUSED

- `FromPaused` discriminator: PAUSED status, or SUSPENDING with no
worker assignment and a `LocalSnapshotInfo` — the field alone is stale
on resumed-from-pause RUNNING actors, so the nil-assignment conjunct is
load-bearing.
- `MarkSuspendingStep` accepts PAUSED and rejects a Data-captured pause
against a Full commit *before* the actor leaves PAUSED (an upload cannot
fabricate memory), using the `content_scope` recorded at pause (#812)
with an `onPause` fallback.
- `CallAteletSuspendStep` paused branch dials by node
(`DialForAteletOnNode`, #813): missing node record ⇒ crash (the snapshot
can never be found); unreachable atelet ⇒ retryable; atelet's
`LOCAL_SNAPSHOT_GONE` ⇒ crash via `maybeCrashActor`.
`FinalizeSuspendedStep` needed no changes thanks to the #813 hoist.
- Root-cause guard: `MarkPausingStep` rejects pausing golden-atespace
actors.
- Docs: pause states + the new `PAUSED → SUSPENDING` edge in the
architecture state diagram; glossary Suspend entry covers both origins.

## Tests

- **atelet unit**: 10 upload-helper subtests (conversion matrix,
idempotency probe, data-loss crash, retryable upload failure) via a
recording object-storage fake; validation table.
- **control-plane unit**: discriminator table, scope-rejection table
(incl. onPause fallback), paused preconditions (no node ⇒ CRASHED, no
atelet ⇒ `ErrNoAteletOnNode` + still SUSPENDING), golden-pause
rejection, prerequisite matrix updated.
- **functional (envtest)**: `TestSuspendActor_FromPaused` (upload called
with the pause snapshot name, no Checkpoint RPC, SUSPENDED, pinning
cleared, ActorSnapshot at the upload destination) +
retry-after-failed-upload (same destination on retry).
- **e2e (demo suite)**: the lifecycle driver gains a suspend-from-PAUSED
mode; three durable-dir cases — Full/Full, Data/Data, and the micro-VM
Full→Data extraction — assert memory/file counters survive the full
pause→suspend→resume journey and the node pinning is gone.

`go test -race ./...` clean (except the pre-existing macOS-only
`internal/atunnel` unix-socket-path failures, untouched by this PR),
`gofmt`/`go vet` clean, protos regenerated via `hack/protoc.sh`.

🤖 Generated with [Claude Code](https://claude.com/claude-code)
2026-08-10 22:34:03 -07:00
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