Added script for cleaning the database

backend/database_cleaning.py

@@ -0,0 +1,69 @@
+'''
+This program will clean the sqlite database every now and then to keep it from exploding.
+
+'''
+
+
+import serial
+import time
+import threading
+import sqlite3
+import copy
+import datetime
+from serial import SerialException
+import configparser
+import random
+
+import logging as log
+log.basicConfig(format='%(asctime)s - %(levelname)s - %(message)s', level=log.INFO)
+
+
+def _initilize_DB(_sqlite_location):
+    _db_conn = sqlite3.connect(_sqlite_location, timeout=60.0)
+    cursor = _db_conn.cursor()
+    cursor.execute("SELECT name FROM sqlite_master WHERE type='table' AND name='Events'")
+    if cursor.fetchone() == None:
+        cursor.execute('''CREATE TABLE Events
+         (UTCUnixTime INTEGER, SubSeconds REAL, TemperatureC REAL, Humidity REAL, AccelX REAL,
+          AccelY REAL, AccelZ REAL, MagX REAL, MagY REAL, MagZ REAL, Pressure REAL, Longitude REAL,
+          Latitude REAL, DetectorName TEXT, DetectorVersion TEXT);''')
+        _db_conn.commit()
+
+
+# settings files
+CONFIG_FILE = "../config/CosmicPi.config"
+
+# read configuration
+# Todo: Put the config parser into a propper class
+# Todo: Implement proper error catching for configparser (e.g. non existent keys or file)
+# read configuration
+config = configparser.ConfigParser()
+config.read(CONFIG_FILE)
+sqlite_location = config.get("Storage", "sqlite_location")
+max_event_age = config.getint("Storage", "sqlite_max_event_age") * 60. * 60.    # here used in seconds
+
+# setup the program
+_initilize_DB(sqlite_location)
+
+# start the cleaning loop
+while(True):
+    # establish a connection
+    db_conn = sqlite3.connect(sqlite_location, timeout=60.0)
+    cursor = db_conn.cursor()
+
+    # delete old events
+    # get the most recent time
+    cursor.execute("SELECT * FROM Events ORDER BY UTCUnixTime DESC, SubSeconds DESC;")
+    latest_time = cursor.fetchone()[0]
+    limit_time = int(latest_time - max_event_age)
+
+    log.info("Deleting entries older than: {} [s]".format(limit_time))
+    # delete old entries and close the connection
+    cursor.execute("DELETE FROM Events WHERE UTCUnixTime < ?;", (limit_time,))
+    db_conn.commit()
+    db_conn.close()
+
+    # sleep for a semi random time
+    time_to_wait = int(random.randrange(5*60, 10*60))
+    log.info("Sleeping for: {} [s]".format(time_to_wait))
+    time.sleep(time_to_wait)