feat: Support for postgis database

This adds support for PostGis database which is
also supported officially by django-- geodjango.

References: #41 #90 #140

Closes #64

Author: EverWinter23

.travis.yml

@@ -9,10 +9,18 @@ services:
   - redis-server
   - mysql
   - postgresql
+addons:
+  postgresql: 9.5
+  apt:
+    packages:
+      - postgresql-9.5-postgis-2.4
+      - gdal-bin
 
 install:
   - pip install tox-travis coverage coveralls codacy-coverage
   - mysql -e 'create database django_prometheus_1;'
+  - psql -U postgres -c 'CREATE DATABASE postgis'
+  - psql -U postgres postgis -c 'CREATE EXTENSION IF NOT EXISTS postgis;'
 script:
   - tox
 after_success:

django_prometheus/db/backends/postgis/__init__.py

@@ -0,0 +1,17 @@
+import psycopg2.extensions
+from django.contrib.gis.db.backends.postgis import base
+from django_prometheus.db.common import DatabaseWrapperMixin, ExportingCursorWrapper
+
+
+class DatabaseWrapper(DatabaseWrapperMixin, base.DatabaseWrapper):
+    def get_connection_params(self):
+        conn_params = super(DatabaseWrapper, self).get_connection_params()
+        conn_params["cursor_factory"] = ExportingCursorWrapper(
+            psycopg2.extensions.cursor, "postgis", self.vendor,
+        )
+        return conn_params
+
+    def create_cursor(self, name=None):
+        # cursor_factory is a kwarg to connect() so restore create_cursor()'s
+        # default behavior
+        return base.DatabaseWrapper.create_cursor(self, name=name)

django_prometheus/db/backends/postgis/base.py

@@ -62,6 +62,15 @@
         "HOST": "localhost",
         "PORT": "5432",
     },
+    # Comment this to not test django_prometheus.db.backends.postgis.
+    "postgis": {
+        "ENGINE": "django_prometheus.db.backends.postgis",
+        "NAME": "postgis",
+        "USER": "postgres",
+        "PASSWORD": "",
+        "HOST": "localhost",
+        "PORT": "5432",
+    },
     # Comment this to not test django_prometheus.db.backends.mysql.
     "mysql": {
         "ENGINE": "django_prometheus.db.backends.mysql",

django_prometheus/tests/end2end/testapp/settings.py

@@ -155,3 +155,30 @@ def testCounters(self):
             alias="mysql",
             vendor="mysql",
         )
+
+
+@skipUnless("postgis" in connections, "Skipped unless postgis database is enabled")
+class TestPostgisDbMetrics(BaseDbMetricTest):
+    """Test django_prometheus.db metrics for postgis backend.
+
+    Note regarding the values of metrics: many tests interact with the
+    database, and the test runner itself does. As such, tests that
+    require that a metric has a specific value are at best very
+    fragile. Consider asserting that the value exceeds a certain
+    threshold, or check by how much it increased during the test.
+    """
+
+    def testCounters(self):
+        r = self.saveRegistry()
+        cursor = connections["postgis"].cursor()
+
+        for _ in range(20):
+            cursor.execute("SELECT 1")
+
+        self.assertMetricCompare(
+            r,
+            lambda a, b: a + 20 <= b < a + 25,
+            "django_db_execute_total",
+            alias="postgis",
+            vendor="postgresql",
+        )