Adds Redis Sentinel backend

Author: Richard O'Dwyer

health_check/contrib/redis_sentinel/__init__.py

@@ -0,0 +1,4 @@
+import django
+
+if django.VERSION < (3, 2):
+    default_app_config = "health_check.contrib.redis.apps.HealthCheckConfig"

health_check/contrib/redis_sentinel/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_sentinel"
+
+    def ready(self):
+        from .backends import RedisSentinelHealthCheck
+
+        plugin_dir.register(RedisSentinelHealthCheck)

health_check/contrib/redis_sentinel/backends.py

@@ -0,0 +1,62 @@
+import logging
+
+from django.conf import settings
+from redis import exceptions, Sentinel
+
+from health_check.backends import BaseHealthCheckBackend
+from health_check.exceptions import ServiceUnavailable
+
+logger = logging.getLogger(__name__)
+
+
+class RedisSentinelHealthCheck(BaseHealthCheckBackend):
+    """Health check for Redis Sentinel."""
+
+    redis_sentinels = getattr(settings, 'REDIS_SENTINELS', ())
+    redis_master_name = getattr(settings, 'REDIS_MASTER_NAME', 'mymaster')
+    redis_sentinels_healthcheck_socket_timeout = getattr(
+        settings, 'REDIS_SENTINELS_HEALTHCHECK_SOCKET_TIMEOUT', 1000
+    )
+
+    def check_status(self, subset=None):
+        """Check Redis service by pinging the redis instance with a redis connection."""
+        logger.debug(
+            'Got %s as the redis_sentinels. Connecting to redis...',
+            self.redis_sentinels,
+        )
+
+        logger.debug('Attempting to connect to redis...')
+        try:
+            client = self._get_redis_client(
+                sentinels=self.redis_sentinels,
+                master_name=self.redis_master_name,
+                timeout=self.redis_sentinels_healthcheck_socket_timeout,
+            )
+            client.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.')
+
+    @staticmethod
+    def _get_redis_client(sentinels, master_name, timeout):
+        sentinel = Sentinel(sentinels, socket_timeout=timeout)
+        return sentinel.master_for(master_name, socket_timeout=timeout)