Ryan Malloy
5e26b34564
Thread-safe connection pool with min/max sizing, lazy growth,
idle recycling, and per-acquire health-check.
API:
pool = informix_db.create_pool(host=..., min_size=1, max_size=10)
with pool.connection() as conn:
...
pool.close()
Design choices:
* Lazy growth from min_size — pre-opens min_size on construction,
grows to max_size on demand. Pay-nothing startup with burst capacity.
* Health-check on acquire, not release. Sends a trivial SELECT 1
round-trip before yielding. Dead idle connections (server-side
timeout, network drop) are silently replaced. The cost is ~1ms
per acquire, bought at the price of "users never see a stale-
connection error". Check-on-release is wrong because idle time
is when connections actually die.
* Eviction on OperationalError/InterfaceError only. The "with
pool.connection()" context manager retains the connection on
application-level errors (ValueError, IntegrityError, etc.).
Avoids the "every constraint violation evicts a healthy connection"
pitfall.
* Releases the pool lock during connect() — the slow handshake
(50-100ms) doesn't serialize other threads' acquires.
Tests: 15 integration tests in test_pool.py covering:
* API & lifecycle (pre-open, lazy growth, context-manager, LIFO)
* Exhaustion (timeout when full, per-acquire override, unblock-on-release)
* Eviction (explicit broken, auto on OperationalError, retain on
application errors)
* Health-check (dead idle silently replaced)
* Shutdown (close drains, idempotent, context-manager)
* Multi-thread safety (8 workers × 3 queries each, no leaks)
Total: 69 unit + 154 integration = 223 tests.
With Phase 14 (TLS) and Phase 15 (pool), the project covers the
three things a typical Python web/API workload needs from a
database driver: PEP 249 surface, TLS transport, connection pool.
Only async (informix_db.aio) remains in the backlog.
informix-db
Pure-Python driver for IBM Informix IDS, speaking the SQLI wire protocol over raw sockets. No IBM Client SDK. No JVM. No native libraries.
Status
🟢 Phase 1 complete. connect() / close() work end-to-end against a real Informix server. Cursor / execute / fetch land in Phase 2.
To our knowledge this is the first pure-socket Informix driver in any language — every other Informix driver (IfxPy, the legacy informixdb, ODBC bridges, Perl DBD::Informix) wraps either IBM's CSDK or the JDBC JAR.
Quick start
import informix_db
with informix_db.connect(
host="127.0.0.1", port=9088,
user="informix", password="in4mix",
database="sysmaster", server="informix",
) as conn:
# cursor() / execute() / fetchone() arrive in Phase 2
pass
Test against the official Informix dev container
docker compose -f tests/docker-compose.yml up -d # IBM Developer Edition, pinned by digest
uv sync --extra dev
uv run pytest # 34 unit tests (no Docker needed)
uv run pytest -m integration # 6 integration tests (needs the container)
Phase 0 artifacts (still useful — they ARE the public reference)
docs/PROTOCOL_NOTES.md— byte-level wire-format reference, derived from packet captures + JDBC decompilation, validated against a real serverdocs/JDBC_NOTES.md— index into the decompiled IBM JDBC driver's wire-protocol classesdocs/DECISION_LOG.md— running rationale for protocol / auth / type decisionsdocs/CAPTURES/— socat hex-dump captures of three reference scenarios (connect, SELECT, full DML cycle)tests/reference/RefClient.java— re-runnable JDBC ground-truth client for capturing fresh traces
License
MIT.