Merge pull request #19 from luizalabs/ro-do_not_open_circuit_duplicated

Check if circuit breaker is open in __exit__ method

.travis.yml

@@ -34,3 +34,4 @@ deploy:
     tags: true
     distributions: "sdist bdist_wheel"
     repo: luizalabs/django-toolkit
+  skip_cleanup: true

django_toolkit/fallbacks/circuit_breaker.py

@@ -34,21 +34,25 @@ def total_failures(self):
         return self.cache.get(self.failure_cache_key) or 0
 
     def open_circuit(self):
+        self.cache.set(self.circuit_cache_key, True, self.circuit_timeout)
+
         logger.critical(
             'Open circuit for {failure_cache_key} {cicuit_cache_key}'.format(
                 failure_cache_key=self.failure_cache_key,
                 cicuit_cache_key=self.circuit_cache_key
             )
         )
 
-        self.cache.set(self.circuit_cache_key, True, self.circuit_timeout)
-
     def __enter__(self):
         if self.is_circuit_open:
             raise self.max_failure_exception
 
+        return self
+
     def __exit__(self, exc_type, exc_value, traceback):
         if exc_type in self.catch_exceptions:
+            if self.is_circuit_open:
+                raise self.max_failure_exception
 
             self._increase_failure_count()
 

tests/fallbacks/test_circuit_breaker.py

@@ -78,7 +78,6 @@ def test_should_open_circuit_when_max_failures_exceeds(self):
         assert cache.get(failure_cache_key, 2)
 
     def test_should_raise_exception_when_circuit_is_open(self):
-
         cache.set('circuit_circuit_open', True)
 
         with pytest.raises(MyException):
@@ -92,3 +91,26 @@ def test_should_raise_exception_when_circuit_is_open(self):
                 success_function()
 
             assert circuit_breaker.is_circuit_open
+
+    def test_should_not_increment_fail_when_circuit_is_open(self):
+        """
+        It should not increment fail count over the max failures limit, when
+        circuit breaker is open after a successful enter.
+        """
+        failure_cache_key = 'fail_count'
+        max_failures = 10
+
+        with pytest.raises(MyException):
+            with CircuitBreaker(
+                cache=cache,
+                failure_cache_key=failure_cache_key,
+                max_failures=max_failures,
+                max_failure_exception=MyException,
+                catch_exceptions=(ValueError,),
+            ) as circuit_breaker:
+                cache.set(failure_cache_key, max_failures)
+                circuit_breaker.open_circuit()
+
+                fail_function()
+
+        assert cache.get(failure_cache_key) == max_failures