[feature] Allowed specifying additional options for InfluxDB backend #…

…458

- Additional options can be specified to the TIMESERIES_DATABASE setting
  which are passed to the underlying backend library. This allows using
  UDP for writing to InfluxDB.
- "openwisp_monitoring.db.backends.influxdb.client.DatabaseClient.write"
  will use "InfluxDBClient.write_points" instead of "InfluxDBClient.write"
  because the former allows writing data using the UDP protocol.

Closes #458

README.rst

@@ -333,6 +333,13 @@ Follow the setup instructions of `openwisp-controller
         'NAME': 'openwisp2',
         'HOST': 'localhost',
         'PORT': '8086',
+        'OPTIONS': {
+            # Specify additional options to be used while initializing
+            # database connection.
+            # Note: These options may differ based on the backend used.
+            'use_udp': True,
+            'udp_port': 8088,
+        }
     }
 
 ``urls.py``:

docker-compose.yml

@@ -16,8 +16,10 @@ services:
     image: influxdb:1.8-alpine
     volumes:
       - influxdb-data:/var/lib/influxdb
+      - ./tests/influxdb.conf:/etc/influxdb/influxdb.conf
     ports:
       - "8086:8086"
+      - "8088:8088/udp"
     environment:
       INFLUXDB_DB: openwisp2
       INFLUXDB_USER: openwisp

openwisp_monitoring/db/backends/influxdb/client.py

@@ -81,6 +81,7 @@ def db(self):
             TIMESERIES_DB['USER'],
             TIMESERIES_DB['PASSWORD'],
             self.db_name,
+            **TIMESERIES_DB.get('OPTIONS', {}),
         )
 
     @retry

tests/influxdb.conf

@@ -0,0 +1,15 @@
+[meta]
+  dir = "/var/lib/influxdb/meta"
+
+[data]
+  dir = "/var/lib/influxdb/data"
+  engine = "tsm1"
+  wal-dir = "/var/lib/influxdb/wal"
+
+[[udp]]
+  enabled = true
+  bind-address = ":8088"
+  database = "openwisp2"
+  batch-size = 0c
+  batch-pending = 0
+  batch-timeout = "0s"

tests/openwisp2/settings.py

@@ -28,7 +28,15 @@
     'NAME': 'openwisp2',
     'HOST': os.getenv('INFLUXDB_HOST', 'localhost'),
     'PORT': '8086',
+    'OPTIONS': {'use_udp': True, 'udp_port': 8088},
 }
+if TESTING:
+    # Some automated tests queries InfluxDB just after
+    # writing the data. Occasionally, the read operation
+    # is performed before InfluxDB has processed the UDP
+    # packet which leads to failing test cases. Therefore,
+    # we always run test suite without UDP support.
+    TIMESERIES_DATABASE['OPTIONS']['use_udp'] = False
 
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