py-circuit-breaker

Python Circuit Breaker Library

Usage

Call the CircuitBreaker logic using a @CircuitBreaker decorator.

@CircuitBreaker(http_client, error_threshold, time_window)
def http_request(host, port):
  conn = http.client.HTTPConnection(host, port)
  conn.request("GET", "/")
  response = conn.getresponse()
  print(response.status, response.reason)

When the underlying function raises an exception, CircuitBreaker opens the circuit for the duration of the time_window.

Execution

Note: Requires docker or a running instance of nginx at localhost:8080 that can be terminated and restarted easily.

docker-compose up -d
python3 py_circuit_breaker/py_circuit_breaker.py

#From another terminal:
docker exec -it nginx /bin/sh -c 'kill 1'

Example Execution

% python3 py_circuit_breaker/py_circuit_breaker.py
200 OK
200 OK
200 OK
200 OK
[Errno 61] Connection refused
[Errno 61] Connection refused
CircuitOpenError: Circuit open for 5 seconds.
200 OK
200 OK
200 OK
200 OK

Tests

python3 setup.py pytest

References

1. https://martinfowler.com/bliki/CircuitBreaker.html