Implement metrics for redis cache (#79)

.travis.yml

@@ -8,6 +8,7 @@ env:
   - DJANGO_VERSION=1.8
 services:
   - memcached
+  - redis
   - mysql
   - postgresql
 matrix:

README.md

@@ -70,7 +70,7 @@ DATABASES = {
 
 ### Monitoring your caches
 
-Filebased and memcached caches can be monitored. Just replace
+Filebased, memcached, redis caches can be monitored. Just replace
 the cache backend to use the one provided by django_prometheus
 `django.core.cache.backends` with `django_prometheus.cache.backends`.
 

django_prometheus/cache/backends/redis.py

@@ -0,0 +1,36 @@
+from django_redis import cache, exceptions
+
+from django_prometheus.cache.metrics import (
+    django_cache_get_fail_total,
+    django_cache_get_total,
+    django_cache_hits_total,
+    django_cache_misses_total,
+)
+
+
+class RedisCache(cache.RedisCache):
+    """Inherit redis to add metrics about hit/miss/interruption ratio"""
+
+    @cache.omit_exception
+    def get(self, key, default=None, version=None, client=None):
+        try:
+            django_cache_get_total.labels(backend='redis').inc()
+            cached = self.client.get(
+                key,
+                default=None,
+                version=version,
+                client=client
+            )
+        except exceptions.ConnectionInterrupted as e:
+            django_cache_get_fail_total.labels(backend='redis').inc()
+            if cache.DJANGO_REDIS_IGNORE_EXCEPTIONS or self._ignore_exceptions:
+                if cache.DJANGO_REDIS_LOG_IGNORED_EXCEPTIONS:
+                    cache.logger.error(str(e))
+                return default
+            raise
+        else:
+            if cached is not None:
+                django_cache_hits_total.labels(backend='redis').inc()
+            else:
+                django_cache_misses_total.labels(backend='redis').inc()
+            return cached or default

django_prometheus/cache/metrics.py

@@ -1,8 +1,15 @@
 from prometheus_client import Counter
 
-django_cache_get_total = Counter('django_cache_get_total',
-                                 'Total get requests on cache', ['backend'])
-django_cache_hits_total = Counter('django_cache_get_hits_total',
-                                  'Total hits on cache', ['backend'])
-django_cache_misses_total = Counter('django_cache_get_misses_total',
-                                    'Total misses on cache', ['backend'])
+django_cache_get_total = Counter(
+    'django_cache_get_total', 'Total get requests on cache', ['backend']
+)
+django_cache_hits_total = Counter(
+    'django_cache_get_hits_total', 'Total hits on cache', ['backend']
+)
+django_cache_misses_total = Counter(
+    'django_cache_get_misses_total', 'Total misses on cache', ['backend']
+)
+django_cache_get_fail_total = Counter(
+    'django_cache_get_fail_total',
+    'Total get request failures by cache', ['backend']
+)

django_prometheus/tests/end2end/testapp/settings.py

@@ -153,6 +153,22 @@ def GetMiddlewareClasses():
     'locmem': {
         'BACKEND': 'django_prometheus.cache.backends.locmem.LocMemCache',
         'LOCATION': '/var/tmp/locmem_cache',
+    },
+    'redis': {
+        'BACKEND': 'django_prometheus.cache.backends.redis.RedisCache',
+        'LOCATION': 'redis://127.0.0.1:6379/1',
+    },
+    # Fake redis config emulated stopped service
+    'stopped_redis': {
+        'BACKEND': 'django_prometheus.cache.backends.redis.RedisCache',
+        'LOCATION': 'redis://127.0.0.1:6666/1',
+    },
+    'stopped_redis_ignore_exception': {
+        'BACKEND': 'django_prometheus.cache.backends.redis.RedisCache',
+        'LOCATION': 'redis://127.0.0.1:6666/1',
+        "OPTIONS": {
+            "IGNORE_EXCEPTIONS": True,
+        }
     }
 }
 

django_prometheus/tests/end2end/testapp/test_caches.py

@@ -1,20 +1,27 @@
-from unittest import skipUnless
+from django.core.cache import caches
+from django.test import TestCase
+from redis import RedisError
 
 from django_prometheus.testutils import PrometheusTestCaseMixin
-from django.test import TestCase
-from django.core.cache import caches
 
 
 class TestCachesMetrics(PrometheusTestCaseMixin, TestCase):
     """Test django_prometheus.caches metrics."""
 
     def testCounters(self):
-        supported_caches = ['memcached', 'filebased', 'locmem']
+        supported_caches = ['memcached', 'filebased', 'locmem', 'redis']
 
         # Note: those tests require a memcached server running
         for supported_cache in supported_caches:
             tested_cache = caches[supported_cache]
 
+            total_before = self.getMetric(
+                'django_cache_get_total', backend=supported_cache) or 0
+            hit_before = self.getMetric(
+                'django_cache_get_hits_total', backend=supported_cache) or 0
+            miss_before = self.getMetric(
+                'django_cache_get_misses_total', backend=supported_cache) or 0
+
             tested_cache.set('foo1', 'bar')
             tested_cache.get('foo1')
             tested_cache.get('foo1')
@@ -25,14 +32,72 @@ def testCounters(self):
             assert result == 'default'
 
             self.assertMetricEquals(
-                4, 'django_cache_get_total', backend=supported_cache)
+                total_before + 4,
+                'django_cache_get_total', backend=supported_cache)
             self.assertMetricEquals(
-                2, 'django_cache_get_hits_total', backend=supported_cache)
+                hit_before + 2,
+                'django_cache_get_hits_total', backend=supported_cache)
             self.assertMetricEquals(
-                2, 'django_cache_get_misses_total', backend=supported_cache)
+                miss_before + 2,
+                'django_cache_get_misses_total', backend=supported_cache)
+
+    def test_redis_cache_fail(self):
+
+        # Note: test use fake service config (like if server was stopped)
+        supported_cache = 'redis'
+
+        total_before = self.getMetric(
+            'django_cache_get_total', backend=supported_cache) or 0
+        fail_before = self.getMetric(
+            'django_cache_get_fail_total', backend=supported_cache) or 0
+        hit_before = self.getMetric(
+            'django_cache_get_hits_total', backend=supported_cache) or 0
+        miss_before = self.getMetric(
+            'django_cache_get_misses_total', backend=supported_cache) or 0
+
+        tested_cache = caches['stopped_redis_ignore_exception']
+        tested_cache.get('foo1')
+
+        self.assertMetricEquals(
+            hit_before,
+            'django_cache_get_hits_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            miss_before,
+            'django_cache_get_misses_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            total_before + 1,
+            'django_cache_get_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            fail_before + 1,
+            'django_cache_get_fail_total', backend=supported_cache
+        )
+
+        tested_cache = caches['stopped_redis']
+        with self.assertRaises(RedisError):
+            tested_cache.get('foo1')
+
+        self.assertMetricEquals(
+            hit_before,
+            'django_cache_get_hits_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            miss_before,
+            'django_cache_get_misses_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            total_before + 2,
+            'django_cache_get_total', backend=supported_cache
+        )
+        self.assertMetricEquals(
+            fail_before + 2,
+            'django_cache_get_fail_total', backend=supported_cache
+        )
 
     def test_cache_version_support(self):
-        supported_caches = ['memcached', 'filebased', 'locmem']
+        supported_caches = ['memcached', 'filebased', 'locmem', 'redis']
 
         # Note: those tests require a memcached server running
         for supported_cache in supported_caches:

requirements.txt

@@ -1,4 +1,5 @@
 Django>=1.8
+django-redis>=4.8
 pep8>=1.6.2
 prometheus-client>=0.0.21
 pip-prometheus>=1.1.0