Getting Started · Circuit Breaker for Requests

Pre-requisites

This is a Python library that works with requests as an adapter. You need to be familiar with requests. We will show you how to integrate your circuit breakers into requests in a way that does not interfere with normal usages.

If you are running on a fixed server, you don't need to spin up Redis and can just go with installing requests-circuit-breaker without any of the optional extras.

You also need to be running Python 3.8. This is supported by AWS Lambdas. The examples here cover how to deploy a python REST endpoint as a Lambda on AWS behind an API Gateway, spin up a Redis backed ElastiCache service and set up an example monitoring web application. You will need an AWS account to try this out. NOTE: Some of these services (e.g. ElastiCache) do not have a free tier so there will be a cost to it.

The deployment code uses the Serverless framework which needs NodeJS installed. See the Serverless documentation for minimum version requirements.

Installing

For the base case, using an in-memory circuit breaker store, run:

$ pip install requests-circuit-breaker

For a Redis backed storage, you need to include the Redis extra requirements:

$ pip install requests-circuit-breaker[Redis]

To include storing failures and monitoring information in DynamoDB, install with the options:

$ pip install requests-circuit-breaker[Redis,Monitor]

Setting up a circuit breaker

You can register multiple circuit breakers, one per base URL that you want to protect.

import requests
from requests_circuit_breaker import CircuitBreakerAdapter
from requests_circuit_breaker import PercentageCircuitBreaker
from requests_circuit_breaker.storage import InMemoryStorage

# Use the default settings
breaker = PercentageCircuitBreaker("my-service", storage=InMemoryStorage())
adapter = CircuitBreakerAdapter(breaker)
session = requests.Session()
session.mount("https://path.to.my/service", adapter)

session.get("https://path.to.my/service/v1/user/123")

When making calls to the service, you need to use session instead of calling requests directly.