Built-in Hooks

pondrs provides two built-in hook implementations.

LoggingHook

Requires the std feature.

Logs pipeline and node lifecycle events using the log crate, with automatic timing:

use pondrs::hooks::LoggingHook;

App::new(catalog, params)
    .with_hooks((LoggingHook::new(),))
    .execute(pipeline)?;

Output (with env_logger at info level):

[INFO] [pipeline] processing - starting
[INFO] [node] clean - starting
[INFO] [node] clean - completed (12.3ms)
[INFO] [node] transform - starting
[INFO] [node] transform - completed (5.1ms)
[INFO] [pipeline] processing - completed (17.8ms)

At debug level, dataset load/save events are also logged:

[DEBUG]   loading readings
[DEBUG]   loaded readings (8.2ms)
[DEBUG]   saving summary
[DEBUG]   saved summary (0.1ms)

LoggingHook uses a TimingTracker internally to measure durations between before/after pairs.

VizHook

Requires the viz feature.

Posts live execution events to a running viz server via HTTP. This enables the interactive visualization to show real-time node status during app run:

use pondrs::viz::VizHook;

App::new(catalog, params)
    .with_hooks((LoggingHook::new(), VizHook::new("http://localhost:8080".into())))
    .execute(pipeline)?;

The typical workflow is:

1. Start the viz server: my_app viz --port 8080
2. In another terminal, run the pipeline with VizHook attached

VizHook is fire-and-forget — it silently ignores HTTP errors, so a missing viz server won’t crash your pipeline. It tracks:

• Node start/end/error events
• Dataset load/save durations

Each event is posted as a VizEvent to POST /api/status, which the viz server broadcasts to connected WebSocket clients.

Combining hooks

Hooks compose as tuples:

.with_hooks((
    LoggingHook::new(),
    VizHook::new("http://localhost:8080".into()),
    my_custom_hook,
))

Each hook receives every event independently. Order in the tuple determines call order, but hooks should not depend on ordering.