config.py

import os
import sqlalchemy

from os import path
from sqlalchemy import create_engine
from shutil import copyfile

db_type = os.environ.get("DB_TYPE") or "mysql"

if (db_type=="sqlite3"): # for testing; use a local sqlite3 file as DB
    
    db_file="instapuller.db"

    if (not path.exists(db_file)): # copy from the template to a new db
        copyfile("misc/instapuller-template.db",db_file)
            
    db = create_engine("sqlite:///"+db_file, echo=True)
elif (db_type=="mysql"): 
    db_user = os.environ.get("DB_USER")
    db_pass = os.environ.get("DB_PASS")
    db_name = os.environ.get("DB_NAME")
    db_connection_type = os.environ.get("DB_CONNECTION_TYPE") or "cloud_sql"

    if (db_connection_type=="direct"):
        db_host=os.environ.get("DB_HOST") or "localhost"
        db = sqlalchemy.create_engine(
            sqlalchemy.engine.url.URL(
                drivername="mysql+pymysql",
                username=db_user,
                password=db_pass,
                database=db_name,
                host=db_host
            ),
            pool_size=5,
            max_overflow=2,
            pool_timeout=30,  # 30 seconds
            pool_recycle=1800,  # 30 minutes
        )
    elif (db_connection_type=="cloud_sql"):
        cloud_sql_connection_name = os.environ.get("CLOUD_SQL_CONNECTION_NAME")

        db = sqlalchemy.create_engine(
            sqlalchemy.engine.url.URL(
                drivername="mysql+pymysql",
                username=db_user,
                password=db_pass,
                database=db_name,
                query={
                    "unix_socket": "/cloudsql/{}".format(cloud_sql_connection_name)
                }
            ),
            pool_size=5,
            max_overflow=2,
            pool_timeout=30,  # 30 seconds
            pool_recycle=1800,  # 30 minutes
        )
    else:
        logger.error("UNKNOWN connection type: " + db_connection_type)
        
else:
    logger.error("UNKNOWN database type: " + db_type)