Signal K SQLite History API Provider

This plugin provides lightweight, dependency-free Signal K History API implementation for systems where installing InfluxDB or other big time series systems is not feasible. The plugin uses node:sqlite bundled in Node.js 22+.

Features

• Zero external dependencies for database operations - uses Node.js's built-in node:sqlite
• Write-Ahead Logging (WAL) for concurrent non-blocking reads and writes
• Batch writing to protect flash storage lifespan
• Configurable allowlist/denylist for filtering which paths to store
• Multi-context support - can store data from other vessels, ATONs, and SAR aircraft

Database Schema

The plugin creates the following tables in a database file inside Signal K plugin data directory (usually ~/.signalk/plugin-config-data/signalk-history-sqlite/sqlite-history/):

• metrics: Dictionary mapping metric names to IDs
• telemetry_real: Real-valued telemetry (numbers)
• telemetry_bool: Boolean telemetry (switches, binary indicators)
• telemetry_string: String telemetry (status flags, mode names, enum values)
• telemetry_json: Reserved for future use (not currently utilized)

History API

This plugin implements the Signal K History API, allowing clients to query historical data:

Get Values

GET /signalk/v2/api/history/values?paths=navigation.speedOverGround,navigation.position&from=2026-01-01T00:00:00Z&to=2026-01-02T00:00:00Z

Supports aggregation methods: average, min, max, first, last, sma, ema

GET /signalk/v2/api/history/values?paths=navigation.speedOverGround:sma:5&from=2026-01-01T00:00:00Z&to=2026-01-02T00:00:00Z

Get Contexts

GET /signalk/v2/api/history/contexts?from=2026-01-01T00:00:00Z&to=2026-01-02T00:00:00Z

Get Paths

GET /signalk/v2/api/history/paths?from=2026-01-01T00:00:00Z&to=2026-01-02T00:00:00Z

Storage Requirements

Storage usage depends on the number of metrics, data frequency, and retention period. With the default 1-second resolution, rough estimates are:

• 1 metric = ~25MB/month
• 100 metrics = ~2.5GB/month

For higher-frequency sampling, storage scales linearly with the sample rate.

License

EUPL-1.2