feat(sqs): rate-limited async message move tasks with cancellation

[vieiralucas]

Summary

Replaces the synchronous-only message-move flow with a rate-aware async mover so callers can observe a moving task in RUNNING state, cancel it mid-flight, and rely on MaxNumberOfMessagesPerSecond as a real ceiling. Part of batch 8/10 of the gap-fill plan.

• StartMessageMoveTask with a rate spawns a background mover that drains one message per tick.
• CancelMessageMoveTask flips an AtomicBool cancellation flag and marks the task CANCELLING; the mover observes the flag on its next tick and finalizes CANCELLED.
• The mover updates messages_moved per move so ListMessageMoveTasks reflects real progress.
• Without a rate, the existing fast path still drains synchronously to COMPLETED (no behavior change for callers that didn't set a rate).
• Cancellation flag lives in a #[serde(skip)] field on MessageMoveTask; snapshots unaffected.

Critical detail noted in the commit body: the mover acquires the state write lock for exactly one move per tick and drops it before sleeping or finalizing — finalize_move_task also takes the write lock and parking_lot's RwLock is non-reentrant.

Test plan

• 129 SQS unit tests pass (cargo test -p fakecloud-sqs --lib)
• 2 new E2E tests in crates/fakecloud-e2e/tests/sqs_message_move.rs (rate-limited drain + mid-flight cancel)
• cargo clippy --workspace --all-targets -- -D warnings clean
• cargo fmt --all clean

---

Summary by cubic

Adds a rate-aware async worker for moving SQS messages with observable progress and mid-flight cancellation. Also fixes an edge case to prevent message loss if the destination queue disappears during a move.

• New Features

  • StartMessageMoveTask with a rate spawns a background worker that moves one message per tick and updates messages_moved.
  • CancelMessageMoveTask sets a cancellation flag and marks CANCELLING; the worker finalizes CANCELLED on the next tick.
  • Progress is visible via ListMessageMoveTasks; tasks end as COMPLETED on drain or FAILED if queues/tasks disappear.
  • No-rate path keeps the previous synchronous drain to COMPLETED.
  • Locking: the worker holds the write lock for one move per tick and releases it before sleeping/finalizing to avoid deadlocks with the non-reentrant RwLock.
  • The cancellation flag is stored in #[serde(skip)] on MessageMoveTask, so snapshots remain unchanged.

• Bug Fixes

  • Prevent message loss when the target queue disappears mid-flight by validating the destination before popping, pushing the message back if a race occurs, and advancing the round-robin index only after a successful commit.

^{Written for commit 911e906. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 3 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="crates/fakecloud-sqs/src/service.rs">

<violation number="1" location="crates/fakecloud-sqs/src/service.rs:852">
P1: Message loss when target queue disappears mid-flight: `pop_front()` removes the message from the source before confirming the destination exists. If the target queue was deleted (or the URL can't be resolved), `msg` is dropped and the message is silently lost. Push the message back onto the source queue on failure, or verify the target before popping.</violation>
</file>

_{Reply with feedback, questions, or to request a fix. Tag @cubic-dev-ai to re-run a review.}

[codecov]

Codecov Report

❌ Patch coverage is 37.01923% with 131 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
crates/fakecloud-sqs/src/service.rs	37.37%	129 Missing ⚠️
crates/fakecloud-sqs/src/state.rs	0.00%	2 Missing ⚠️

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