undertow_llm

Wrap any LLM call, get caching, retries, rate limiting, and a real-time dashboard — with zero code changes to your model.

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Problem Statement

Without an observability and resilience layer, production LLM applications suffer from soaring API costs due to redundant prompt calls, unexpected provider outages with zero fallback protection, and complete lack of visibility into latency and errors. undertow_llm solves this by wrapping your existing Python LLM functions in a single decorator—providing semantic caching, automated retries, rate limiting, and a live dashboard without modifying your model logic.

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Install

pip install undertow-llm

Or install with provider & production backend extras:

pip install "undertow-llm[gemini]"    # Google Gemini support
pip install "undertow-llm[ollama]"    # Ollama local model support
pip install "undertow-llm[postgres]"  # PostgreSQL + pgvector backend
pip install "undertow-llm[redis]"     # Redis rate-limiting backend
pip install "undertow-llm[prod]"      # Production stack (Postgres + Redis)

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Quickstart

Before (bare LLM call — no caching, no fallback, no observability):

def generate_response(prompt: str) -> str:
    return client.models.generate_content("gemini-2.5-flash", prompt).text

After (wrapped with @track() — fully resilient & tracked):

from undertow_llm import track

@track(cache=True, retries=3, rate_limit_rate=2.0)
def generate_response(prompt: str) -> str:
    return client.models.generate_content("gemini-2.5-flash", prompt).text

Copy-paste into your application and run. Zero edits required except setting your provider API key.

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Real-Time Dashboard

Start the live observability dashboard in one command:

undertow-llm serve

Open http://localhost:8080 to inspect real-time metrics, cache hit ratios, latency charts, cost estimates, distributed traces, and request logs.

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How It Works

1. The @track() decorator wraps your function, intercepting incoming prompts before execution.
2. It performs a vector similarity search (using SentenceTransformers) to serve semantic cache hits instantly and applies token-bucket rate limits.
3. Upon function completion, it records latency, token usage, estimated cost, and execution traces to storage.
4. It is provider-agnostic because it wraps your Python function call directly and never touches your underlying model SDK.

For a detailed architectural breakdown of the 8-stage execution pipeline and backend dispatcher, see ARCHITECTURE.md.

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Configuration

Local dev needs zero config — defaults out-of-the-box to local SQLite (undertow_llm.db).

For production environments, configure via environment variables or configure():

Environment Variable	Default	Description
UNDERTOW_LLM_POSTGRES_URL	None (SQLite)	PostgreSQL URL with pgvector for production vector storage & metrics
UNDERTOW_LLM_REDIS_URL	None (Local)	Redis URL for distributed rate limiting & token buckets
UNDERTOW_LLM_DB_PATH	"undertow-llm.db"	File path for local SQLite database fallback
UNDERTOW_LLM_DASHBOARD_PORT	8080	HTTP port for undertow-llm serve dashboard

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@track() Parameter Reference

Parameter	Type	Default	Description
cache	bool	True	Enable semantic caching for responses
similarity_threshold	float	0.92	Cosine similarity threshold for cache hits (0.0 to 1.0)
cache_ttl	int | None	None	Optional time-to-live in seconds for cached entries
retries	int	3	Max retry attempts for transient LLM failures
base_delay	float	1.0	Initial exponential backoff delay (seconds)
max_delay	float	60.0	Cap on exponential backoff delay (seconds)
jitter	bool	True	Add randomized jitter to retry delays to prevent thundering herds
retry_on	tuple	(Exception,)	Exception types that trigger automatic retries
fallback	list	[]	Ordered list of fallback functions to call if primary function fails
rate_limit_rate	float	2.0	Token-bucket refill rate (tokens/second)
rate_limit_max_tokens	float	10.0	Token-bucket maximum capacity (burst limit)
max_concurrency	int | None	None	Max concurrent executions allowed across processes
cost_per_call	float | None	None	Explicit cost override per call ($/call)
policy	callable | None	None	Custom safety hook returning "allow", "block", or "flag"
canary	dict | None	None	Canary routing config {"fn": alternate_fn, "weight": 0.10}

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Supported Providers

undertow_llm works with any provider — OpenAI, Anthropic, Google Gemini, Ollama, HuggingFace, or custom local models — since it wraps your existing Python function call rather than a specific provider SDK.

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Examples

See demo/example_usage.py for complete runnable examples.

1. Multi-Provider Fallback Chain

from undertow_llm import track

def fallback_anthropic(prompt: str) -> str:
    return anthropic_client.messages.create(model="claude-3-5-sonnet", messages=[{"role": "user", "content": prompt}]).content[0].text

@track(retries=2, fallback=[fallback_anthropic])
def primary_openai(prompt: str) -> str:
    return openai_client.chat.completions.create(model="gpt-4o", messages=[{"role": "user", "content": prompt}]).choices[0].message.content

2. Streaming LLM Response

@track(cache=False)
def stream_gemini(prompt: str):
    response = gemini_client.models.generate_content_stream("gemini-2.5-flash", prompt)
    for chunk in response:
        yield chunk.text

3. Local Model (Ollama) with Custom Usage Extractor

@track(
    cost_per_call=0.0,  # Local model — zero API cost
    usage_extractor=lambda res: {"prompt_tokens": len(res.get("prompt", "")), "completion_tokens": len(res.get("response", ""))}
)
def ask_ollama(prompt: str) -> dict:
    return ollama.generate(model="llama3", prompt=prompt)

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Known Limitations & Roadmap

Limitations

• SQLite Concurrency: Local SQLite storage (undertow_llm.db) is zero-config and ideal for development and single-instance apps, but is not designed for multi-node production scale. For high concurrency, set UNDERTOW_LLM_POSTGRES_URL and UNDERTOW_LLM_REDIS_URL.

Near-Term Roadmap

• OpenTelemetry trace exporter integration
• Multi-tenant workspace tagging & dashboard authentication
• Automated PII redaction and sensitive prompt masking filters

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Contributing

Contributions are welcome! Please see CONTRIBUTING.md for developer setup instructions.

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License

MIT — see LICENSE