Spanda

Deterministic Replay

Record and replay simulation traces for regression and incident analysis.

Recording

spanda sim rover.sd --record

Produces a JSON mission trace (.trace, version 2 when state snapshots are present) with scheduler events, provider dispatch events (provider_call with module, function, and provider key), and embedded robot state (pose, velocity, e-stop, active mode) on each recorded frame.

Replay modes

Inspect frames (default):

spanda replay mission.trace
spanda replay mission.trace --from T+00:30

Deterministic verification — re-run the source program and compare event sequences:

spanda replay mission.trace --deterministic

Frame-by-frame playback — apply recorded state snapshots without re-executing program logic:

spanda replay mission.trace --playback

Playback uses wall-clock pacing between frames by default. Offsets accept milliseconds or T+mm:ss / T+hh:mm:ss forms.

Twin replay integrates with existing twin { replay true; } blocks.

Incident workflow (Phase 24)

Combine mission trace recording, twin export, and optional cloud upload for post-incident review:

# 1. Record a mission trace during simulation
spanda sim examples/showcase/autonomous_rover/src/rover.sd --record

# 2. Export twin replay JSON
spanda twin export examples/communication/twin_replay_golden.sd --out incident-replay.json

# 3. Optional cloud upload (mock HTTP server in CI)
export SPANDA_CLOUD_UPLOAD_URL=http://127.0.0.1:18770/upload
./scripts/twin_cloud_golden_path.sh

Golden path index: tier-3-golden-paths.md

Digital twin replay export (JSON)

Export the twin replay buffer after simulation for post-incident review:

spanda twin export examples/communication/twin_replay_golden.sd --out twin-replay.json
spanda sim examples/showcase/digital_twin_demo.sd --twin-export twin-replay.json

JSON shape:

{
  "twin": "RobotTwin",
  "mirrors": ["pose", "velocity"],
  "frame_count": 12,
  "frames": [
    { "frame": 0, "fields": { "pose": { "...": "..." } } }
  ]
}

Golden traces in git

Runtime --record output is ignored by default (*.trace in .gitignore). Committed reference traces are allowed under:

See realtime.

This site is open source. Improve this page.