Configuring the storage backend
===============================

Purgatory can share the state of its circuits between many instances using
a redis server.

With this strategy, when a service has been restarted, it starts with
the circuit breaker state.

To choose a storage backend, the unit of work has to be configured.

Using asynchronous API
----------------------

.. important::

   Extra dependency ``redis`` is required. can be installed using

   ::

      pip install "purgatory[redis]"


::

   import httpx
   from purgatory import AsyncCircuitBreakerFactory, AsyncRedisUnitOfWork

   circuit_breaker = AsyncCircuitBreakerFactory(
      default_threshold=5,
      default_ttl=30,
      exclude=[
         (httpx.HTTPStatusError, lambda exc: exc.response.is_client_error),
      ],
      uow=AsyncRedisUnitOfWork("redis://localhost/0"),
   )

   await circuit_breaker.initialize()


Using synchronous API
---------------------


.. important::

   Extra dependency ``redis`` is required. can be installed using

   ::

      pip install "purgatory[redis]"


::

   import requests
   from purgatory import SyncCircuitBreakerFactory, SyncRedisUnitOfWork

   circuit_breaker = SyncCircuitBreakerFactory(
      default_threshold=5,
      default_ttl=30,
      exclude=[
         (requests.HTTPError, lambda exc: 400 <= exc.response.status_code < 500),
      ],
      uow=SyncRedisUnitOfWork("redis://localhost/0"),
   )


.. important::

   When using the AsyncRedisUnitOfWork, the coroutine ``initialize`` must
   be called to initialize the redis connection.

   The synchronous client has this method because it is autogenerated,
   but it cannot not be used.