Oleksandr Bezdieniezhnykh
2.8 KiB
FDR And Observability
1. High-Level Overview
Purpose: Record bounded, replayable mission evidence and expose runtime health/status events for analysis and operator awareness.
Architectural Pattern: Append-only event sink + exporter.
Upstream dependencies: All runtime components.
Downstream consumers: Validation harness, post-flight audit tools, QGC status through MAVLink component.
2. Internal Interfaces
Interface: FlightRecorder
| Method | Input | Output | Async | Error Types |
|---|---|---|---|---|
append_event |
FdrEvent |
AppendResult |
Yes | RecorderUnavailable, StorageFull |
rollover |
RolloverRequest |
FdrSegmentInfo |
No | RolloverFailed |
export |
ExportRequest |
ExportResult |
Yes | ExportFailed |
3. Data Access Patterns
| Query | Frequency | Hot Path | Index Needed |
|---|---|---|---|
| Append event | High | Yes | Append index only |
| Export by time/type | Post-flight | No | Time/type index |
Storage Estimates
| Table/Collection | Est. Row Count | Row Size | Total Size | Growth Rate |
|---|---|---|---|---|
| FDR events | Flight-dependent | Mixed | <=64 GB per 8 h | Per flight |
4. Implementation Details
State Management: Owns active segment, rollover policy, and export state.
Key Dependencies:
| Library | Purpose |
|---|---|
| PostgreSQL client | Event metadata, time/type indexes, mission query surface |
| CBOR writer | Bounded runtime payload segments |
| Parquet writer | Optional post-flight export |
Error Handling Strategy:
- Storage-full emits critical status and starts rollover/retention behavior.
- Append failures are surfaced to the caller and health system.
5. Caveats & Edge Cases
Known limitations:
- Raw frames are not retained by default; only metadata, decisions, hashes, and occlusion/blackout status are recorded.
- PostgreSQL availability is required for indexed FDR metadata; CBOR payload segments preserve bounded append behavior for high-volume data.
Performance bottlenecks:
- FDR appends must not block hot-path localization.
6. Dependency Graph
Must be implemented after: event schema and key DTOs.
Can be implemented in parallel with: MAVLink integration.
Blocks: release evidence and most validation reports.
7. Logging Strategy
| Log Level | When | Example |
|---|---|---|
| ERROR | Recorder unavailable | fdr_unavailable path=... |
| WARN | Rollover occurs | fdr_rollover segment=... |
| INFO | Export complete | fdr_export_complete format=parquet |
Log format: FDR event metadata plus local health logs.
Log storage: PostgreSQL FDR event tables plus CBOR segment payloads.