Add Redis Health Check (#225)

.travis.yml

@@ -10,6 +10,8 @@ env:
   - DJANGO=111
   - DJANGO=22
   - DJANGO=master
+services:
+  - redis-server
 matrix:
   fast_finish: true
   allow_failures:

README.rst

@@ -73,6 +73,7 @@ Add the ``health_check`` applications to your ``INSTALLED_APPS``:
         'health_check.contrib.psutil',              # disk and memory utilization; requires psutil
         'health_check.contrib.s3boto_storage',      # requires boto and S3BotoStorage backend
         'health_check.contrib.rabbitmq',            # requires RabbitMQ broker
+        'health_check.contrib.redis',               # required Redis broker
     ]
 
 (Optional) If using the ``psutil`` app, you can configure disk and memory
@@ -99,6 +100,12 @@ on django.conf.settings with the required format to connect to your rabbit serve
 
     BROKER_URL = amqp://myuser:mypassword@localhost:5672/myvhost
 
+To use the Redis healthcheck, please make sure that there is a variable named ``REDIS_URL``
+on django.conf.settings with the required format to connect to your redis server. For example:
+
+.. code::
+
+    REDIS_URL = redis://localhost:6370
 
 Setting up monitoring
 ---------------------

health_check/contrib/rabbitmq/backends.py

@@ -38,4 +38,4 @@ def check_status(self):
         except BaseException as e:
             self.add_error(ServiceUnavailable("Unknown error"), e)
         else:
-            logger.debug("Connection estabilished. RabbitMQ is healthy.")
+            logger.debug("Connection established. RabbitMQ is healthy.")

health_check/contrib/redis/__init__.py

@@ -0,0 +1 @@
+default_app_config = 'health_check.contrib.redis.apps.HealthCheckConfig'

health_check/contrib/redis/apps.py

@@ -0,0 +1,12 @@
+from django.apps import AppConfig
+
+from health_check.plugins import plugin_dir
+
+
+class HealthCheckConfig(AppConfig):
+    name = "health_check.contrib.redis"
+
+    def ready(self):
+        from .backends import RedisHealthCheck
+
+        plugin_dir.register(RedisHealthCheck)

health_check/contrib/redis/backends.py

@@ -0,0 +1,35 @@
+import logging
+
+from django.conf import settings
+from redis import exceptions, from_url
+
+from health_check.backends import BaseHealthCheckBackend
+from health_check.exceptions import ServiceUnavailable
+
+logger = logging.getLogger(__name__)
+
+
+class RedisHealthCheck(BaseHealthCheckBackend):
+    """Health check for Redis."""
+
+    redis_url = getattr(settings, "REDIS_URL", 'redis://localhost/1')
+
+    def check_status(self):
+        """Check Redis service by pinging the redis instance with a redis connection."""
+        logger.debug("Got %s as the redis_url. Connecting to redis...", self.redis_url)
+
+        logger.debug("Attempting to connect to redis...")
+        try:
+            # conn is used as a context to release opened resources later
+            with from_url(self.redis_url) as conn:
+                conn.ping()  # exceptions may be raised upon ping
+        except ConnectionRefusedError as e:
+            self.add_error(ServiceUnavailable("Unable to connect to Redis: Connection was refused."), e)
+        except exceptions.TimeoutError as e:
+            self.add_error(ServiceUnavailable("Unable to connect to Redis: Timeout."), e)
+        except exceptions.ConnectionError as e:
+            self.add_error(ServiceUnavailable("Unable to connect to Redis: Connection Error"), e)
+        except BaseException as e:
+            self.add_error(ServiceUnavailable("Unknown error"), e)
+        else:
+            logger.debug("Connection established. Redis is healthy.")

requirements-dev.txt

@@ -9,3 +9,4 @@ pydocstyle
 pep8-naming
 pytest<4
 pytest-django
+redis==3.3.8

setup.cfg

@@ -32,11 +32,12 @@ setup_requires =
     sphinx
     pytest-runner
 tests_require =
+    mock
     pytest
     pytest-cov
     pytest-django
     celery
-    mock
+    redis
 
 [bdist_wheel]
 universal = 1

tests/test_redis.py

@@ -0,0 +1,88 @@
+import mock
+from redis.exceptions import ConnectionError, TimeoutError
+
+from health_check.contrib.redis.backends import RedisHealthCheck
+
+
+class TestRedisHealthCheck:
+    """Test Redis health check."""
+
+    @mock.patch("health_check.contrib.redis.backends.getattr")
+    @mock.patch("health_check.contrib.redis.backends.from_url", autospec=True)
+    def test_redis_refused_connection(self, mocked_connection, mocked_getattr):
+        """Test when the connection to Redis is refused."""
+        mocked_getattr.return_value = "redis_url"
+
+        # mock returns
+        mocked_connection.return_value = mock.MagicMock()
+        mocked_connection.return_value.__enter__.side_effect = ConnectionRefusedError("Refused connection")
+
+        # instantiates the class
+        redis_healthchecker = RedisHealthCheck()
+
+        # invokes the method check_status()
+        redis_healthchecker.check_status()
+        assert len(redis_healthchecker.errors), 1
+
+        # mock assertions
+        mocked_connection.assert_called_once_with('redis://localhost/1')
+
+    @mock.patch("health_check.contrib.redis.backends.getattr")
+    @mock.patch("health_check.contrib.redis.backends.from_url")
+    def test_redis_timeout_error(self, mocked_connection, mocked_getattr):
+        """Test Redis TimeoutError."""
+        mocked_getattr.return_value = "redis_url"
+
+        # mock returns
+        mocked_connection.return_value = mock.MagicMock()
+        mocked_connection.return_value.__enter__.side_effect = TimeoutError("Timeout Error")
+
+        # instantiates the class
+        redis_healthchecker = RedisHealthCheck()
+
+        # invokes the method check_status()
+        redis_healthchecker.check_status()
+        assert len(redis_healthchecker.errors), 1
+
+        # mock assertions
+        mocked_connection.assert_called_once_with('redis://localhost/1')
+
+    @mock.patch("health_check.contrib.redis.backends.getattr")
+    @mock.patch("health_check.contrib.redis.backends.from_url")
+    def test_redis_con_limit_exceeded(self, mocked_connection, mocked_getattr):
+        """Test Connection Limit Exceeded error."""
+        mocked_getattr.return_value = "redis_url"
+
+        # mock returns
+        mocked_connection.return_value = mock.MagicMock()
+        mocked_connection.return_value.__enter__.side_effect = ConnectionError("Connection Error")
+
+        # instantiates the class
+        redis_healthchecker = RedisHealthCheck()
+
+        # invokes the method check_status()
+        redis_healthchecker.check_status()
+        assert len(redis_healthchecker.errors), 1
+
+        # mock assertions
+        mocked_connection.assert_called_once_with('redis://localhost/1')
+
+    @mock.patch("health_check.contrib.redis.backends.getattr")
+    @mock.patch("health_check.contrib.redis.backends.from_url")
+    def test_redis_conn_ok(self, mocked_connection, mocked_getattr):
+        """Test everything is OK."""
+        mocked_getattr.return_value = "redis_url"
+
+        # mock returns
+        mocked_connection.return_value = mock.MagicMock()
+        mocked_connection.return_value.__enter__.side_effect = True
+
+        # instantiates the class
+        redis_healthchecker = RedisHealthCheck()
+
+        # invokes the method check_status()
+        redis_healthchecker.check_status()
+        assert len(redis_healthchecker.errors), 0
+
+        # mock assertions
+        mocked_connection.assert_called_once_with('redis://localhost/1')