# Stop an Axum worker while it waits for queued input

Graceful HTTP shutdown does not automatically stop a separately spawned worker. Give the worker a token, use a cancellation-safe channel receive, signal the token with server shutdown, and await the JoinHandle before the process exits.

Save this requirement in Perch and check it after each agent edit. The rule gives your agent a named check to run, a finding to repair, and the same command to recheck.

## Implement the Axum boundary

Save this illustrative integration module as `src/worker.rs`.

```rust
use tokio::sync::mpsc;
use tokio_util::sync::CancellationToken;

pub async fn run_worker(mut jobs: mpsc::Receiver<String>, stop: CancellationToken) {
    loop {
        tokio::select! {
            _ = stop.cancelled() => break,
            message = jobs.recv() => {
                match message {
                    Some(job) => {
                        if stop.is_cancelled() { break; }
                        process(job).await;
                    },
                    None => break,
                }
            }
        }
    }
}

async fn process(_job: String) {
    tokio::task::yield_now().await;
}
```

The order, inventory, or resource-lifetime scenario is adapted from Perch’s public [order-service source at commit 4af67af](https://github.com/lakeday-org/perch/blob/4af67af46d76ac99398d61c7ad0a45441760d4dc/test/fixtures/order-service/storage.py). This Axum implementation is an illustrative adaptation.

## Integrate with your application

Create a bounded mpsc channel and spawn this task under the application owner. Wire the same shutdown signal into axum::serve(...).with_graceful_shutdown. The process function is a stand-in for your delivery operation: real work needs its own timeout, cooperative cancellation and retry policy. Do not blindly cancel a partially completed external side effect; persist/reconcile its outcome. tokio::select drops losing futures, so verify cancellation safety when replacing recv with another I/O operation.



## Exercise the boundary and failure paths

| Scenario | Expected outcome |
| --- | --- |
| Worker blocked with no jobs | Cancellation ends loop |
| Sender drops | None ends loop |
| Pending delivery when shutdown arrives | Delivery-specific timeout/recovery policy applies |
| Process exits | JoinHandle awaited, no detached worker |

Add regression tests for these cases in your existing Axum test project. Use separate connections or deliberately reordered completion where the case involves concurrency; a sequential happy-path test does not exercise that failure. Run the test command after creating the matching test file or suite:

```sh
cargo test worker_shutdown
```

The scenarios above specify tests to implement. A completed Perch source check below is separate from running these application integration tests.

## Introduce the specific agent regression

In a throwaway copy, replace this source span:

```rust
_ = stop.cancelled() => break,
```

with:

```rust
// Remove the source span shown above.
```

Run the relevant negative test and the Perch command on that broken copy. Restore the corrected source before committing the application. The supplied mutation reproduces the exact regression for the rule check.

## Preserve the requirement as a Perch rule

Save this in `.perch/rules/perch-guide-axum-owned-worker-shutdown.yaml` at the repository root, keeping your existing `perch.yaml`:

```yaml
- name: worker-has-shutdown-branch
  where: "src/worker.rs"
  ensure: >-
    run_worker must select on stop.cancelled and break on cancellation, rather than wait indefinitely for another message.
```

Install and authenticate the CLI once, then check the current working file:

```sh
npm install -g @lakeday/perch
perch login
perch check src/worker.rs --rules worker-has-shutdown-branch --json
```

Use Node 22 or newer. The framework can use another language; Perch’s CLI remains a Node command. A gated finding exits 3. Exits 1 or 2 mean the check did not complete and must be reported as a blocker.

## Inspect the captured rule check

On 2026-10-14, Perch using jev-latest checked the exact fixed and broken source provided here. The capture records SHA-256 hashes of both sources and the requirement.

| Source control | Exit | Outcome |
| --- | --- | --- |
| Broken | 3 | Rule finding |
| Corrected | 0 | No rule finding |

The rule distinguished these controls in this run. [Raw Perch capture](/owned-worker-shutdown/capture.json) · [Exact sources and mutation](/owned-worker-shutdown/source.json).

## Install the rule pack and configure your agent

[Download this rule pack ZIP](/owned-worker-shutdown/rule-pack.zip) · [Download the YAML rules](/owned-worker-shutdown/rules.yaml) · [Agent task](/owned-worker-shutdown/agent-task.txt). The pack contains the rule, its example paths and the repair/recheck instructions. Review the `where` selector before using it in an existing project. Keep your root `perch.yaml`; install this rule as a separate file under `.perch/rules/`.

1. Install Perch using Node 22 or newer and sign in once:

```sh
npm install -g @lakeday/perch
perch login
```

2. Download the pack, inspect it, and extract it from your repository root. The extraction preserves any existing files:

```sh
curl -fL 'https://reporules.fyi/axum/owned-worker-shutdown/rule-pack.zip' -o 'perch-guide-axum-owned-worker-shutdown.zip'
unzip -n 'perch-guide-axum-owned-worker-shutdown.zip'
```

The installed rule is `.perch/rules/perch-guide-axum-owned-worker-shutdown.yaml`. Its selector matches `src/worker.rs` in this example; adapt the selector to your application file before checking an existing project.

3. Configure the coding agent you use. Run one of these commands:

Claude Code:

```sh
perch setup claude-code
```

Codex:

```sh
perch setup codex
```

Cursor:

```sh
perch setup cursor
```

Pi:

```sh
perch setup pi
```

4. Ask the agent to edit the implementation and check the saved requirement:

> Use the installed Perch skill while editing src/worker.rs. Preserve worker-has-shutdown-branch. Run perch check src/worker.rs --rules worker-has-shutdown-branch --json after the edit. Read each finding and the affected code, fix the implementation, and run the identical check again after the fix. Keep the rule and regression tests intact. Run the application's relevant regression tests and report the commands and actual results. Exit 3 means a rule finding; exit 1 or 2 means the check did not complete. Report an unavailable or incomplete check as blocked. Do not claim the application tests ran if only the Perch check ran.

5. After repairing a finding, run the same check again and inspect the result:

```sh
perch check src/worker.rs --rules worker-has-shutdown-branch --json
```

Commit the downloaded rule and the installed agent configuration with your application. The rule file adds no guarantee of correctness; keep the regression tests from this guide.

With the base reference fetched, use `perch scan --since origin/main --filter type=lint` in CI.

## Framework references and verification scope

- [tokio.rs reference](https://tokio.rs/tokio/topics/shutdown)
- [docs.rs reference](https://docs.rs/tokio/latest/tokio/macro.select.html)

The dated capture records the source check shown above. Implement the adapters, schema and regression tests described in this guide in your application. Unchanged requests reuse cached answers; fresh model judgments can vary. Model analysis sends relevant source to the configured service.