Replace shutdown channels with CancellationToken

[mickvandijke]

Summary

• Replace tokio::sync::broadcast and tokio::sync::watch shutdown channels with tokio_util::CancellationToken in Devnet and RunningNode
• Shut down devnet nodes concurrently via join_all instead of sequentially
• Simplify shutdown select branches — CancellationToken::cancelled() needs no extra borrow-check, removing nested if guards

Test plan

• cargo build --release compiles cleanly
• cargo test passes all existing tests
• Devnet startup/shutdown cycle completes without hanging

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR updates devnet and node shutdown signaling to use tokio_util::CancellationToken, and adjusts health monitoring to match a now-synchronous is_running check.

Changes:

• Replace broadcast/watch shutdown channels with CancellationToken in Devnet and RunningNode
• Shut down devnet nodes concurrently via futures::future::join_all
• Update health monitor checks to call is_running() synchronously (no .await)

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
tests/e2e/testnet.rs	Updates health monitor to use non-async is_running()
src/node.rs	Replaces watch shutdown signaling with CancellationToken in RunningNode
src/devnet.rs	Replaces broadcast shutdown signaling with CancellationToken and concurrently shuts down nodes
Cargo.toml	Adds tokio-util dependency for CancellationToken

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[Copilot]

CancellationToken lives under tokio_util::sync and typically requires enabling the tokio-util crate's sync feature. With only features = [\"rt\"], this may fail to compile. Consider switching to tokio-util = { version = \"0.7\", features = [\"sync\"] } (or include both \"sync\" and any other needed features).

Suggested change

	tokio-util = { version = "0.7", features = ["rt"] }
	tokio-util = { version = "0.7", features = ["rt", "sync"] }

[greptile-apps]

Greptile Overview

Greptile Summary

Refactored shutdown signaling from broadcast/watch channels to CancellationToken in both Devnet and RunningNode, simplifying shutdown logic and enabling concurrent devnet node shutdown.

Key changes:

• Added tokio-util dependency for CancellationToken support
• Devnet: Replaced broadcast::Sender<()> with CancellationToken, enabling parallel shutdown of all nodes via join_all
• RunningNode: Replaced watch::Sender<bool> and watch::Receiver<bool> with single CancellationToken, eliminating channel state checks
• Removed SHUTDOWN_CHANNEL_CAPACITY constant (no longer needed)
• Updated health monitors to use shutdown.cancelled() instead of channel receive
• Fixed is_running() call in test to use synchronous API

Note: The PR description mentions DHT-based routing and self-node filtering, but these features are not part of this PR (they were merged in PR #8). This PR only contains the CancellationToken refactor.

Confidence Score: 5/5

• This PR is safe to merge with minimal risk
• The refactor is straightforward, well-tested, and follows Rust best practices. CancellationToken is a proven pattern that simplifies shutdown logic. All changes maintain equivalent semantics while removing boilerplate. No .unwrap(), .expect(), or panic!() violations per CLAUDE.md style guide. The parallel shutdown implementation correctly uses .take() to transfer ownership.
• No files require special attention

Important Files Changed

Filename	Overview
Cargo.toml	Added tokio-util dependency with rt feature for CancellationToken support
src/devnet.rs	Replaced broadcast channels with CancellationToken for shutdown signaling; parallelized node shutdown with join_all; removed unused constant
src/node.rs	Replaced watch channels with CancellationToken for shutdown signaling; simplified shutdown logic by removing channel state checks
tests/e2e/testnet.rs	Updated is_running() call to synchronous method (removed .await), consistent with P2PNode API

Sequence Diagram

sequenceDiagram
    participant Caller
    participant Devnet
    participant ShutdownSignal
    participant HealthMonitor
    participant DevnetNode
    participant P2PNode

    Note over Devnet,ShutdownSignal: Shutdown Initiated
    Caller->>Devnet: shutdown()
    Devnet->>ShutdownSignal: cancel()
    
    par Health Monitor Shutdown
        ShutdownSignal-->>HealthMonitor: cancelled() fires
        HealthMonitor->>HealthMonitor: exit loop
    and Node Shutdown (parallel for all nodes)
        Devnet->>DevnetNode: take p2p_node
        Devnet->>P2PNode: shutdown().await
        P2PNode-->>Devnet: Result
        Devnet->>DevnetNode: set state to Stopped
    end
    
    Devnet-->>Caller: shutdown complete

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

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[Copilot]

The async block pushed into shutdown_futures is not spawned as a task or wrapped in a future that will execute independently. Since join_all expects futures that are already running or self-contained, this code will execute the shutdown logic sequentially when join_all polls each future, defeating the purpose of concurrent shutdown. Spawn each shutdown as a tokio task (e.g., tokio::spawn(async move { ... })) and collect the join handles instead.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

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[Copilot]

Missing import for futures crate. The code uses futures::future::join_all but there is no corresponding use futures statement at the top of the file. This will cause a compilation error. Add use futures or use futures::future to the imports.

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.

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[dirvine]

Clean refactor: broadcast/watch shutdown channels → CancellationToken. Concurrent shutdown via join_all is a solid improvement. All CI gates pass. LGTM.