Rate limiting and authentication in LangChain

Introduction

Rate limiting helps control how often users can use a service. Authentication checks who the user is. Together, they keep services safe and fair.

When you want to stop too many requests from one user in a short time.

When you need to check if a user has permission to use your API.

When you want to protect your service from abuse or overload.

When you want to track usage per user or app.

When you want to require users to log in before accessing features.

Syntax

LangChain

from langchain import RateLimiter, Authentication

# Create a rate limiter
rate_limiter = RateLimiter(max_calls=5, period=60)  # 5 calls per 60 seconds

# Create an authentication object
auth = Authentication(api_key='your_api_key')

# Use them in your LangChain calls
response = some_langchain_function(
    input_data,
    rate_limiter=rate_limiter,
    authentication=auth
)

The RateLimiter controls how many calls happen in a time window.

The Authentication object holds credentials like API keys.

Examples

This sets a limit of 10 calls every 60 seconds.

LangChain

rate_limiter = RateLimiter(max_calls=10, period=60)  # 10 calls per minute

This sets up authentication using an API key.

LangChain

auth = Authentication(api_key='abc123')

Use rate limiting without authentication.

LangChain

response = some_langchain_function(input_data, rate_limiter=rate_limiter)

Use authentication without rate limiting.

LangChain

response = some_langchain_function(input_data, authentication=auth)

Sample Program

This example tries to make 5 calls but only 3 are allowed every 10 seconds. It uses authentication with an API key. Calls beyond the limit will fail.

LangChain

from langchain import RateLimiter, Authentication

# Set up rate limiter: max 3 calls per 10 seconds
rate_limiter = RateLimiter(max_calls=3, period=10)

# Set up authentication with a fake API key
auth = Authentication(api_key='testkey123')

# Simulate calling a LangChain function with both
for i in range(5):
    try:
        response = some_langchain_function(
            input_data=f"Request {i+1}",
            rate_limiter=rate_limiter,
            authentication=auth
        )
        print(f"Call {i+1}: Success")
    except Exception as e:
        print(f"Call {i+1}: Failed - {e}")

Important Notes

Rate limiting helps prevent your service from being overwhelmed.

Always keep your API keys secret and never share them publicly.

Check error messages to handle when limits are reached gracefully.

Summary

Rate limiting controls how often users can call your service.

Authentication verifies who is using your service.

Using both keeps your service safe and fair for everyone.