SecantusDB 0.3.0a4

A drop-in single-node MongoDB server in Python using the WiredTiger storage engine

SecantusDB

[!WARNING] Alpha software.

SecantusDB is in early development. The API surface and on-disk format can change between point releases. The wire-protocol behaviour and driver compatibility are stabilising — but if you adopt SecantusDB as a single-node mongod replacement today, be prepared to lose on-disk data on upgrade. Production deployments that need durable data across upgrades should still run a real mongod.

Drop-in MongoDB for single-node applications. SecantusDB is a real MongoDB server written in Python: it speaks the MongoDB wire protocol on the same TCP socket a mongod would, so any standard MongoDB driver or tool — pymongo, mongo-go-driver, mongosh, mongodump / mongorestore — connects unchanged. Point a MongoClient at it and your application code doesn't know the difference, as long as the application only needs single-node behaviour. No mongod to install, no port conflicts, parallel-test friendly, embedded or as a standalone daemon (secantusdb).

Single-node only by design: replica sets, sharding, and anything that depends on real cluster topology are out of scope. Within that single-node scope, SecantusDB is the database your driver thinks it's talking to — same handshake, same wire frames, same error codes.

from pymongo import MongoClient
from secantus import SecantusDBServer

# On-disk by default at ./secantus-data; pass storage_path=":memory:" for ephemeral.
with SecantusDBServer(port=27017) as server:
    client = MongoClient(server.uri)
    db = client["mydb"]
    db["users"].insert_one({"_id": 1, "name": "Joe"})
    assert db["users"].find_one({"_id": 1})["name"] == "Joe"

Storage engine

SecantusDB uses the same WiredTiger C library mongod ships — vendored at vendor/wiredtiger/ (mongodb-7.0.33), built from source into the wheel, called via WT's official Python SWIG bindings. There is no Python re-implementation of the storage engine: B-trees, page eviction, write-ahead logging, durability, on-disk format are all pure WiredTiger. Your data lives on the same battle-tested engine mongod uses.

That doesn't make SecantusDB as fast as mongod — the layers above storage (command dispatch, query planner, aggregation pipeline) are Python, and a like-for-like benchmark currently has SecantusDB ~8×–46× slower per operation than mongod. CRUD reads sit near the lower end of that; bulk update / delete and aggregation sit at the upper end where Python loop overhead dominates. See docs/benchmark.md for current numbers and methodology. The right use is tests, dev, embedded apps, and single-node prototypes where conformance + WT durability matter more than per-op latency.

What's in scope

Everything a single-node application needs from the wire — the handshake (hello / isMaster / ping / buildInfo / ...), CRUD (insert / find / update / delete / findAndModify / count / drop), cursors with getMore / killCursors, aggregation pipelines and the expression language they need, and change streams (single-node, oplog-backed; collection / db / cluster scope; resume tokens; fullDocument: "updateLookup"; pre-images via fullDocumentBeforeChange; blocking awaitData getMore). All backed by a real query planner with index acceleration — single-field, compound, mixed-direction, partial, TTL, sort — proper explain output (IXSCAN vs COLLSCAN), and a hash-join $lookup.

Authentication: SCRAM-SHA-256 — MongoDB's default since 4.0 — is implemented end-to-end on the wire. Off by default; flip on with secantusdb --auth (or SecantusDBServer(..., require_auth=True)), provision users with createUser, then connect with the standard MongoClient(uri, username=, password=) shape. See Authentication. Authorization (RBAC), x509, LDAP, Kerberos, and TLS are not implemented — an authenticated principal is currently treated as fully privileged.

What's out of scope: real replica sets, sharding, RBAC, x509 / LDAP / Kerberos auth, TLS, text / geo / wildcard indexes, $where, real transaction rollback. If you need those, run a real mongod.

Installation

pip install SecantusDB

Pre-built wheels are published for CPython 3.10, 3.11, 3.12, and 3.13 on:

• macOS arm64 (Apple Silicon)
• Linux x86_64 and aarch64 (manylinux2014 / glibc, and musllinux_1_2 / Alpine)
• Windows AMD64

macOS Intel (x86_64) is not in the wheel matrix; use a from-source install if you need it.

WiredTiger is vendored inside the wheel — no separate package, no compile step, no system build tools required.

Building from source (unsupported platforms only)

If your platform isn't in the matrix above, pip install SecantusDB falls back to the sdist and compiles WiredTiger from source. That needs three native build tools on PATH:

• cmake (>= 3.21)
• ninja
• swig (>= 4.0)

Platform	Install prerequisites
macOS (Homebrew)	brew install cmake ninja swig
Debian/Ubuntu	sudo apt-get install -y cmake ninja-build swig
Fedora/RHEL	sudo dnf install -y cmake ninja-build swig
Alpine	apk add --no-cache cmake ninja swig build-base

See Installation for dev-install instructions.

Standalone daemon (drop-in mongod replacement)

pip install puts a secantusdb script on your PATH. Run it like you'd run mongod:

secantusdb --host 127.0.0.1 --port 27017
# storage at ./secantus-data by default; pass --storage-path :memory:
# for an ephemeral temp dir cleaned up on shutdown.

Then point any MongoDB driver or tool at it — no application code changes, just the URI:

mongosh mongodb://127.0.0.1:27017
mongodump --uri mongodb://127.0.0.1:27017 --out ./dump

from pymongo import MongoClient
client = MongoClient("mongodb://127.0.0.1:27017")  # same code as for mongod

The conformance gauges back this up: pymongo's own test suite and mongo-go-driver's own test suite run unmodified against SecantusDB — see pymongo validation report and Go-driver validation report.

Examples

A walk through the operations a typical application exercises — connect, insert, index, query, drop. Full version with explanations: examples in the docs.

from pymongo import MongoClient
from secantus import SecantusDBServer

# Ephemeral here so the snippet is self-contained; the production default
# is on-disk at ./secantus-data — drop storage_path or set a real path.
with SecantusDBServer(port=0, storage_path=":memory:") as server:
    client = MongoClient(server.uri)
    cellar = client["wine_cellar"]
    bottles = cellar["bottles"]

    # --- Insert ---
    bottles.insert_one(
        {"_id": 1, "name": "Pommard 2018", "region": "Burgundy", "year": 2018}
    )
    bottles.insert_many(
        [
            {"_id": 2, "name": "Brunello 2015", "region": "Tuscany", "year": 2015},
            {"_id": 3, "name": "Barolo 2017", "region": "Piedmont", "year": 2017},
            {"_id": 4, "name": "Pommard 2020", "region": "Burgundy", "year": 2020},
        ]
    )

    # --- Indexes ---
    bottles.create_index([("year", 1)])                     # single-field
    bottles.create_index([("region", 1), ("year", -1)])     # compound

    # --- Query ---
    drinkable_now = list(
        bottles.find({"year": {"$lte": 2018}}).sort("year")
    )
    assert [b["name"] for b in drinkable_now] == [
        "Brunello 2015",
        "Barolo 2017",
        "Pommard 2018",
    ]

    by_region = list(
        bottles.aggregate(
            [
                {"$group": {"_id": "$region", "count": {"$sum": 1}}},
                {"$sort": {"_id": 1}},
            ]
        )
    )

    # --- Drop ---
    bottles.drop()                              # one collection
    client.drop_database("wine_cellar")         # whole database

Documentation

Full docs are in docs/; build them with uv run python -m invoke docs and open docs/_build/html/index.html. Highlights:

• Quickstart — embedding in tests, running standalone.
• Architecture — the layered design.
• Indexes — what find() and aggregate accelerate, explain semantics, hints, partial indexes, TTL.
• Aggregation — supported pipeline stages and expression operators.
• Compatibility — the divergences you should know about before you point an application at SecantusDB.
• pymongo validation report — per-category pass / fail / skip rate from running pymongo's own test suite, unmodified, against SecantusDB. The submodule at vendor/pymongo-tests/ is checked out at the pinned upstream tag with zero local edits; a pytest plugin starts an embedded server and points pymongo's DB_IP/DB_PORT at it.
• Go-driver validation report — same shape against mongo-go-driver's own test suite, unmodified. Spawns a standalone SecantusDB daemon and runs go test with MONGODB_URI pointed at it. The Go driver underpins mongodump / mongorestore and most non-Python tooling, so this gauge catches type-strict wire bugs (int32 vs int64) that pymongo accepts silently.
• Node-driver validation report — same shape against mongo-node-driver's own test suite, unmodified. Spawns a standalone SecantusDB daemon and runs mocha with MONGODB_URI pointed at it. Initial baseline is restricted to the import-clean subset of unit tests because of an unrelated ESM/TypeScript loader quirk in node-mongodb-native v7.2.0; see node_validation/include_paths.py for the rationale.
• Java-driver validation report — same shape against mongo-java-driver's own test suite, unmodified. Spawns a standalone SecantusDB daemon and invokes the driver's bundled ./gradlew with -Dorg.mongodb.test.uri=mongodb://.... Initial baseline is the :bson:test module (BSON serialization, ~289 test files); the JDBC-style integration modules can be added to java_validation/include_modules.py as we widen.

Development

git clone https://github.com/jdrumgoole/SecantusDB.git
cd SecantusDB
uv sync --extra dev
uv run python -m pytest    # 584 tests, runs in parallel under pytest-xdist

Common workflows:

uv run python -m invoke fmt    # ruff format
uv run python -m invoke lint   # ruff check
uv run python -m invoke test   # pytest, parallel
uv run python -m invoke docs   # build Sphinx docs (warnings as errors)

License

SecantusDB is dual-licensed:

• Code — GPL-2.0-only. See LICENSE. SecantusDB bundles the WiredTiger storage engine (itself GPL-2/GPL-3), so the combined work is GPL.
• Written content — Creative Commons Attribution 4.0 International (CC-BY 4.0). See LICENSE-DOCS. Covers README.md, everything under docs/, the validation reports, and pymongo_validation/README.md. Operational instructions to AI assistants (CLAUDE.md) and vendored third-party content (under vendor/) are out of scope.