perf(daemon): bridge tracing events to /ws/logs (partial #66)

[zackees]

Summary

• Adds BroadcastLogLayer (crates/fbuild-daemon/src/log_layer.rs), a tracing-subscriber Layer that forwards events to the existing BroadcastHub::log_tx channel so /ws/logs subscribers see the same output the daemon writes to stderr.
• Native ESP32 write-flash progress already emits via tracing::info!() in fbuild-deploy::esp32_native; this layer makes those per-region and 10%-throttled progress lines visible on the WebSocket stream — closing the follow-up from the perf(deploy): replace esptool subprocess with espflash native crate #66 code comments / issue comment without adding a separate progress API.
• BroadcastHub is constructed in main.rs before tracing init and threaded into DaemonContext::with_hub(...) so the layer can be registered against log_tx before the first tracing::info!.

Behavior notes

• Zero subscribers → one atomic load per event (no JSON, no allocation).
• Events from fbuild_daemon::handlers::websockets are filtered out so the /ws/logs handler's own connect/disconnect notices don't feed themselves back onto the channel they announce.
• Payload shape matches the welcome frame /ws/logs already emits: {"type":"log","level":..,"message":..,"timestamp":..,"module":..} — clients parse every line with one schema.
• Partial for issue perf(deploy): replace esptool subprocess with espflash native crate #66: this addresses the WebSocket progress-bridge follow-up. The core esptool → espflash migration landed earlier (PRs spike(deploy): add espflash crate + feasibility module (partial #66) #74 / perf(deploy): use espflash crate for verify-flash (partial #66) #89 / perf(deploy): use espflash crate for write-flash (partial #66) #106).

Test plan

• uv run cargo check -p fbuild-daemon --all-targets
• uv run cargo clippy -p fbuild-daemon --all-targets -- -D warnings
• uv run cargo test -p fbuild-daemon --lib (111 passed; 4 new log_layer tests)
• Manual: open /ws/logs against a local daemon during an ESP32 deploy with FBUILD_USE_ESPFLASH_WRITE=1 and confirm progress frames stream live.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Refactor
  • Enhanced logging pipeline architecture to better support live log streaming via WebSocket.
  • Improved flexibility in how broadcast channels are initialized and supplied within the daemon infrastructure.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro

Run ID: e4e86f92-af01-4fef-8470-432ae3e77a32

📥 Commits

Reviewing files that changed from the base of the PR and between 53a077a and 5ad1d78.

📒 Files selected for processing (4)

• crates/fbuild-daemon/src/context.rs
• crates/fbuild-daemon/src/lib.rs
• crates/fbuild-daemon/src/log_layer.rs
• crates/fbuild-daemon/src/main.rs

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📝 Walkthrough

Walkthrough

The changes introduce a broadcast logging layer that intercepts tracing events and publishes them to a shared channel, enabling external components to subscribe to log messages. A new BroadcastLogLayer is implemented, DaemonContext gains a constructor accepting an external BroadcastHub, and main.rs wires these components together with the tracing subscriber pipeline.

Changes

Cohort / File(s)	Summary
Logging Layer Implementation crates/fbuild-daemon/src/log_layer.rs	New BroadcastLogLayer struct implementing tracing_subscriber::Layer to intercept events, render them as JSON with metadata, and broadcast via a shared channel. Includes optimization to skip serialization when no receivers exist and filters out WebSocket module events.
Daemon Infrastructure crates/fbuild-daemon/src/context.rs, crates/fbuild-daemon/src/lib.rs	Added DaemonContext::with_hub() constructor accepting external BroadcastHub; refactored new() to delegate to it. Exported log_layer module for public access.
Daemon Initialization crates/fbuild-daemon/src/main.rs	Updated tracing subscriber setup to include BroadcastLogLayer wired to a shared broadcast channel. Switched DaemonContext construction to use with_hub(), passing the configured BroadcastHub instance.

Sequence Diagram

sequenceDiagram
    participant App as Application
    participant TS as Tracing System
    participant BLL as BroadcastLogLayer
    participant Hub as BroadcastHub
    participant WS as WebSocket Handler

    App->>TS: Emit tracing event
    TS->>BLL: Invoke on_event()
    alt Receivers exist
        BLL->>BLL: Render message + fields
        BLL->>BLL: Serialize to JSON
        BLL->>Hub: Broadcast message
        Hub->>WS: Send to subscribers
    else No receivers
        BLL->>BLL: Skip (early return)
    end

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Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Poem

🐰 A hop through the logs we now shall take,
Tracing events dance in the wake,
Broadcast channels sing with glee,
WebSocket friends shall always see,
The daemon's heart laid bare and free! 📡✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch perf/daemon-broadcast-log-layer

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