tombstone-sdk 0.2.0

Tombstone Python SDK — server-side feature flag evaluation with OpenFeature support

Tombstone Python SDK

The official Python SDK for Tombstone — production intelligence layer for feature flags.

Installation

pip install tombstone

Quick Start

from tombstone import TombstoneClient

client = TombstoneClient(
    api_url="http://localhost:8081",
    sdk_key="sdk-dev-token-change-in-prod",
    environment="development",
)
client.initialize()

enabled = client.is_enabled("my-first-flag", {"user_id": "user-123"})
print(f"Feature enabled: {enabled}")

Configuration

Parameter	Type	Required	Default	Description
api_url	str	Yes	—	Base URL of your Tombstone flag-api service
sdk_key	str	Yes	—	SDK authentication token (set via FLAG_API_TOKEN in infra/.env)
environment	str	No	"production"	Environment name (development, staging, production)
cache_ttl	int	No	30	Flag cache TTL in seconds
timeout	float	No	5.0	HTTP request timeout in seconds
stream_url	str	No	None	Gateway SSE URL for real-time updates (e.g. http://localhost:8080)

from tombstone import TombstoneClient

client = TombstoneClient(
    api_url="http://localhost:8081",
    sdk_key="sdk-dev-token-change-in-prod",
    environment="staging",
    cache_ttl=60,
    timeout=3.0,
    stream_url="http://localhost:8080",
)
client.initialize()

Usage

is_enabled()

Returns True if the flag is enabled for the given evaluation context.

# Simple boolean flag
enabled = client.is_enabled("my-first-flag", {"user_id": "user-123"})

# With richer context for targeting rules
enabled = client.is_enabled("checkout-v2", {
    "user_id": "user-123",
    "email": "[e-mail]",
    "plan": "pro",
    "country": "US",
})

if enabled:
    show_new_checkout()
else:
    show_legacy_checkout()

get_variation()

Returns the variation value for multivariate flags. Use when you need string/number/JSON values rather than a boolean.

# String variation
theme = client.get_variation("ui-theme", {"user_id": "user-123"}, default="light")
# Returns: "light", "dark", or "high-contrast"

# JSON variation
config = client.get_variation("pricing-config", {"user_id": "user-123"}, default={})
# Returns: {"monthly": 29, "annual": 249}

# Numeric variation
limit = client.get_variation("rate-limit-tier", {"user_id": "user-123"}, default=100)

Async Support

The SDK ships an async client for use with asyncio, FastAPI, and other async frameworks.

import asyncio
from tombstone import AsyncTombstoneClient

async def main():
    client = AsyncTombstoneClient(
        api_url="http://localhost:8081",
        sdk_key="sdk-dev-token-change-in-prod",
        environment="development",
    )
    await client.initialize()

    enabled = await client.is_enabled("my-first-flag", {"user_id": "user-123"})
    print(f"Feature enabled: {enabled}")

    await client.close()

asyncio.run(main())

FastAPI integration

from contextlib import asynccontextmanager
from fastapi import FastAPI, Request
from tombstone import AsyncTombstoneClient

client: AsyncTombstoneClient

@asynccontextmanager
async def lifespan(app: FastAPI):
    global client
    client = AsyncTombstoneClient(
        api_url="http://localhost:8081",
        sdk_key="sdk-dev-token-change-in-prod",
        environment="production",
    )
    await client.initialize()
    yield
    await client.close()

app = FastAPI(lifespan=lifespan)

@app.get("/checkout")
async def checkout(request: Request, user_id: str):
    enabled = await client.is_enabled("checkout-v2", {"user_id": user_id})
    return {"checkout_version": "v2" if enabled else "v1"}

Local Development

Start the full Tombstone stack first:

git clone https://github.com/sairam0424/Tombstone.git
cd Tombstone
cp infra/.env.example infra/.env
make dev

The flag-api will be available at http://localhost:8081. The default SDK token is sdk-dev-token-change-in-prod (set via FLAG_API_TOKEN in infra/.env).

# Local development client — no changes needed
client = TombstoneClient(
    api_url="http://localhost:8081",
    sdk_key="sdk-dev-token-change-in-prod",
    environment="development",
)

Testing

Use TombstoneTestClient for unit tests — it evaluates flags locally without any network calls.

from tombstone.testing import TombstoneTestClient

def test_checkout_page():
    client = TombstoneTestClient()
    client.set_flag("checkout-v2", enabled=True)
    client.set_variation("ui-theme", "dark")

    # Your application code under test
    result = render_checkout(client)

    assert result["checkout_version"] == "v2"
    assert result["theme"] == "dark"

def test_checkout_page_disabled():
    client = TombstoneTestClient()
    client.set_flag("checkout-v2", enabled=False)

    result = render_checkout(client)

    assert result["checkout_version"] == "v1"

TombstoneTestClient implements the same interface as TombstoneClient, so you can inject it via dependency injection or monkeypatching.

Requirements

• Python 3.10+
• httpx (HTTP client)
• pydantic v2 (config validation)

No other runtime dependencies.