Added possibility to export metrics of several caches backends (#69)

* Added metrics for filebased cache

* Added more backends and more testings

* Fix 2.7 compatibility

* fix typos

* Removed unwanted comments

Author: geobeau

.gitignore

@@ -91,5 +91,8 @@ tramp
 # cask packages
 .cask/
 
+# venv
+venv/
+
 ### Prometheus ###
 examples/prometheus/data

.travis.yml

@@ -7,13 +7,14 @@ env:
   - DJANGO_VERSION=1.11
   - DJANGO_VERSION=1.8
 services:
+  - memcached
   - mysql
   - postgresql
 matrix:
   exclude:
     - python: "2.7"
       env: DJANGO_VERSION=2.0
-      
+
 install:
   - pip install -r requirements.txt
   - pip install -q Django==$DJANGO_VERSION

README.md

@@ -68,6 +68,21 @@ DATABASES = {
 }
 ```
 
+### Monitoring your caches
+
+Filebased and memcached 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`.
+
+```python
+CACHES = {
+    'default': {
+        'BACKEND': 'django_prometheus.cache.backends.filebased.FileBasedCache',
+        'LOCATION': '/var/tmp/django_cache',
+    }
+}
+```
+
 ### Monitoring your models
 
 You may want to monitor the creation/deletion/update rate for your

django_prometheus/cache/__init__.py

@@ -0,0 +1,19 @@
+from django_memcached_consul import memcached
+from django_prometheus.cache.metrics import (
+    django_cache_get_total, django_cache_hits_total, django_cache_misses_total)
+
+
+class MemcachedCache(memcached.MemcachedCache):
+    """Inherit django_memcached_consul to add metrics about hit/miss ratio"""
+
+    def get(self, key, default=None, version=None):
+        django_cache_get_total.labels(backend='django_memcached_consul').inc()
+        cached = super(MemcachedCache, self).get(
+            key, default=None, version=None)
+        if cached is not None:
+            django_cache_hits_total.labels(
+                backend='django_memcached_consul').inc()
+        else:
+            django_cache_misses_total.labels(
+                backend='django_memcached_consul').inc()
+        return cached

django_prometheus/cache/backends/__init__.py

@@ -0,0 +1,17 @@
+from django.core.cache.backends import filebased
+from django_prometheus.cache.metrics import (
+    django_cache_get_total, django_cache_hits_total, django_cache_misses_total)
+
+
+class FileBasedCache(filebased.FileBasedCache):
+    """Inherit filebased cache to add metrics about hit/miss ratio"""
+
+    def get(self, key, default=None, version=None):
+        django_cache_get_total.labels(backend='filebased').inc()
+        cached = super(FileBasedCache, self).get(
+            key, default=None, version=None)
+        if cached is not None:
+            django_cache_hits_total.labels(backend='filebased').inc()
+        else:
+            django_cache_misses_total.labels(backend='filebased').inc()
+        return cached

django_prometheus/cache/backends/django_memcached_consul.py

@@ -0,0 +1,19 @@
+from django.core.cache.backends import memcached
+from django_prometheus.cache.metrics import (
+    django_cache_get_total, django_cache_hits_total, django_cache_misses_total)
+
+
+class MemcachedCache(memcached.MemcachedCache):
+    """Inherit memcached to add metrics about hit/miss ratio"""
+
+    def get(self, key, default=None, version=None):
+        django_cache_get_total.labels(backend='memcached').inc()
+        cached = super(MemcachedCache, self).get(
+            key, default=None, version=None)
+        if cached is not None:
+            django_cache_hits_total.labels(
+                backend='memcached').inc()
+        else:
+            django_cache_misses_total.labels(
+                backend='memcached').inc()
+        return cached

django_prometheus/cache/backends/filebased.py

@@ -0,0 +1,8 @@
+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_prometheus/cache/backends/memcached.py

@@ -135,6 +135,22 @@ def GetMiddlewareClasses():
     },
 }
 
+# Caches
+
+CACHES = {
+    'default': {
+        'BACKEND': 'django_prometheus.cache.backends.memcached.MemcachedCache',
+        'LOCATION': 'localhost:11211',
+    },
+    'memcached': {
+        'BACKEND': 'django_prometheus.cache.backends.memcached.MemcachedCache',
+        'LOCATION': 'localhost:11211',
+    },
+    'filebased': {
+        'BACKEND': 'django_prometheus.cache.backends.filebased.FileBasedCache',
+        'LOCATION': '/var/tmp/django_cache',
+    }
+}
 
 # Internationalization
 # https://docs.djangoproject.com/en/1.8/topics/i18n/