main_mysql_pooling.py

# Copyright 2018 Google LLC
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# [START gae_python38_cloudsql_mysql_pooling]
# [START gae_python3_cloudsql_mysql_pooling]
import os

from flask import Flask
import sqlalchemy

db_user = os.environ.get("CLOUD_SQL_USERNAME")
db_password = os.environ.get("CLOUD_SQL_PASSWORD")
db_name = os.environ.get("CLOUD_SQL_DATABASE_NAME")
db_connection_name = os.environ.get("CLOUD_SQL_CONNECTION_NAME")

# When deployed to App Engine, the `GAE_ENV` environment variable will be
# set to `standard`
if os.environ.get("GAE_ENV") == "standard":
    # If deployed, use the local socket interface for accessing Cloud SQL
    unix_socket = f"/cloudsql/{db_connection_name}"
    engine_url = "mysql+pymysql://{}:{}@/{}?unix_socket={}".format(
        db_user, db_password, db_name, unix_socket
    )
else:
    # If running locally, use the TCP connections instead
    # Set up Cloud SQL Proxy (cloud.google.com/sql/docs/mysql/sql-proxy)
    # so that your application can use 127.0.0.1:3306 to connect to your
    # Cloud SQL instance
    host = "127.0.0.1"
    engine_url = "mysql+pymysql://{}:{}@{}/{}".format(
        db_user, db_password, host, db_name
    )

# The Engine object returned by create_engine() has a QueuePool integrated
# See https://docs.sqlalchemy.org/en/latest/core/pooling.html for more
# information
engine = sqlalchemy.create_engine(engine_url, pool_size=3)

app = Flask(__name__)


@app.route("/")
def main():
    cnx = engine.connect()
    cursor = cnx.execute("SELECT NOW() as now;")
    result = cursor.fetchall()
    current_time = result[0][0]
    # If the connection comes from a pool, close() will send the connection
    # back to the pool instead of closing it
    cnx.close()

    return str(current_time)


# [END gae_python3_cloudsql_mysql_pooling]
# [END gae_python38_cloudsql_mysql_pooling]


if __name__ == "__main__":
    app.run(host="127.0.0.1", port=8080, debug=True)