knx-telegram-store

A standalone, host-agnostic Python library for KNX telegram persistence.

Features

• Canonical Data Model: A unified model for KNX telegrams shared between Home Assistant and SpectrumKNX.
• Pluggable Backends:
  • In-Memory: Fast, deque-based storage with full filtering support.
  • SQLite: Lightweight persistent storage with SQL-based filtering.
  • PostgreSQL + TimescaleDB: Full-scale time-series storage.
• Unified Query Model: Powerful declarative filtering including time-delta context windows and pagination.
• Stats & Maintenance: get_stats() reports count, covered time range and on-disk size; evict_older_than() supports dry runs; optimize() reclaims disk space (VACUUM).
• Read-Only Mode: Open a SQLite store owned and written by another process (e.g. Home Assistant's KNX telegram store) without running migrations or allowing writes.
• Concurrent Access: Writing SQLite stores use WAL journaling and a busy timeout, so a single writer and multiple (cross-process) readers coexist safely.
• Capability Flags: store.capabilities declares what a backend supports (supports_optimize, supports_size_stats, read_only, …) so hosts can gate UI instead of hardcoding backends.
• Zero Runtime Dependencies: Core library (model, interface, in-memory) has no dependencies.
• Automated Schema Management: SQL backends handle their own creation and upgrades.

Installation

pip install knx-telegram-store

For SQL support:

pip install knx-telegram-store[sqlite]
pip install knx-telegram-store[postgres]

Usage

from datetime import datetime
from knx_telegram_store import StoredTelegram, TelegramQuery
from knx_telegram_store.backends.memory import MemoryStore

async def main():
    store = MemoryStore(max_size=1000)
    await store.initialize()

    telegram = StoredTelegram(
        timestamp=datetime.now(),
        source="1.1.1",
        destination="1/1/1",
        telegramtype="GroupValueWrite",
        direction="Incoming",
        value=22.5,
        unit="°C"
    )

    await store.store(telegram)

    query = TelegramQuery(destinations=["1/1/1"])
    result = await store.query(query)
    
    for t in result.telegrams:
        print(f"{t.timestamp}: {t.source} -> {t.destination} | {t.value} {t.unit}")

    await store.close()

Stats, purging and space reclamation

from datetime import UTC, datetime, timedelta
from knx_telegram_store.backends.sqlite import SqliteStore

store = SqliteStore("/data/telegrams.db", retention_days=90)
await store.initialize()

stats = await store.get_stats()
print(f"{stats.telegram_count} telegrams, {stats.size_bytes} bytes, "
      f"{stats.oldest_timestamp} .. {stats.newest_timestamp}")

cutoff = datetime.now(UTC) - timedelta(days=30)
would_delete = await store.evict_older_than(cutoff, dry_run=True)  # preview only
deleted = await store.evict_older_than(cutoff)

# Deleting rows does not shrink the database on disk by itself:
if store.capabilities.supports_optimize:
    await store.optimize()  # VACUUM — blocks writers, can take a while on large DBs

Read-only access to a shared store

Another process (e.g. Home Assistant's KNX integration) owns and writes the database; you only want to read it:

store = SqliteStore("/homeassistant/.storage/knx/telegrams.db", read_only=True)
await store.initialize()   # never runs DDL/migrations against a foreign schema

if await store.needs_migration():
    ...  # schema is older/newer than this library version — surface a warning

result = await store.query(TelegramQuery(limit=100))
await store.store(telegram)  # raises KnxTelegramStoreException — writes rejected

The file is opened with SQLite's mode=ro, so writes are impossible at the driver level. capabilities.read_only is True and supports_optimize is False in this mode. Writing stores enable WAL journaling, which makes this single-writer/multi-reader setup safe across processes.

Validating a config / connection

Before triggering an expensive operation such as a migration, you can validate that a store is reachable. Both checks return a structured ConnectionCheckResult (ok, kind, message, detail) instead of raising.

from knx_telegram_store import ConnectionErrorKind
from knx_telegram_store.backends.sqlite import SqliteStore
from knx_telegram_store.backends.postgres import PostgresStore

# Static, side-effect-free config validation (before constructing a store):
#  - SQLite: sync — checks the file is writeable or can be created
result = SqliteStore.check_config("/data/telegrams.db")
#    (with read_only=True: checks the file exists and is readable instead)
result = SqliteStore.check_config("/data/telegrams.db", read_only=True)
#  - Postgres: async — actually connects to verify user/password/host/port/database
result = await PostgresStore.check_config("postgresql://user:pw@host:5432/knx")

if not result.ok:
    print(f"[{result.kind}] {result.message}")  # e.g. [auth] Authentication failed ...

# Live probe of an already-constructed store (no migrations, no schema changes):
store = SqliteStore("/data/telegrams.db")
result = await store.check_connection()
if result.kind is ConnectionErrorKind.OK:
    await store.initialize()

License

MIT