172 lines
6.0 KiB
Python
172 lines
6.0 KiB
Python
#------------------------------------------------------------------------------
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# Copyright (c) 2022, Oracle and/or its affiliates.
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#
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# This software is dual-licensed to you under the Universal Permissive License
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# (UPL) 1.0 as shown at https://oss.oracle.com/licenses/upl and Apache License
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# 2.0 as shown at http://www.apache.org/licenses/LICENSE-2.0. You may choose
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# either license.
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#
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# If you elect to accept the software under the Apache License, Version 2.0,
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# the following applies:
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# https://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#------------------------------------------------------------------------------
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#------------------------------------------------------------------------------
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# connection_pool.py
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#
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# Demonstrates the use of connection pooling using a Flask web application.
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#
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# Connection Pools can significantly reduce connection times for long running
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# applications that repeatedly open and close connections. Connection pools
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# allow multiple, concurrent web requests to be efficiently handled. Internal
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# features help protect against dead connections, and also aid use of Oracle
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# Database features such as FAN and Application Continuity.
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#
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# To run this sample, install Flask with:
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# pip install --upgrade Flask
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#
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# The default route will display a welcome message:
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# http://127.0.0.1:8080/
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#
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# To find a username you can pass an id, for example 1:
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# http://127.0.0.1:8080/user/1
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#
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# To insert new a user 'fred' you can call:
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# http://127.0.0.1:8080/post/fred
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#
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#------------------------------------------------------------------------------
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import os
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import oracledb
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from flask import Flask
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import sample_env
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# Port to listen on
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port=int(os.environ.get('PORT', '8080'))
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# determine whether to use python-oracledb thin mode or thick mode
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if not sample_env.get_is_thin():
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oracledb.init_oracle_client(lib_dir=sample_env.get_oracle_client())
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#------------------------------------------------------------------------------
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# start_pool(): starts the connection pool
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def start_pool():
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# Generally a fixed-size pool is recommended, i.e. pool_min=pool_max. Here
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# the pool contains 4 connections, which will allow 4 concurrent users.
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pool_min = 4
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pool_max = 4
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pool_inc = 0
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pool = oracledb.create_pool(user=sample_env.get_main_user(),
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password=sample_env.get_main_password(),
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dsn=sample_env.get_connect_string(),
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min=pool_min,
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max=pool_max,
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increment=pool_inc,
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session_callback=init_session)
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return pool
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# init_session(): a 'session callback' to efficiently set any initial state
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# that each connection should have.
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#
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# This particular demo doesn't use dates, so sessionCallback could be omitted,
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# but it does show the kinds of settings many apps would use.
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#
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# If you have multiple SQL statements, then call them all in a PL/SQL anonymous
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# block with BEGIN/END so you only use execute() once. This is shown later in
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# create_schema().
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#
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def init_session(connection, requestedTag_ignored):
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with connection.cursor() as cursor:
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cursor.execute("""
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alter session set
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time_zone = 'UTC'
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nls_date_format = 'YYYY-MM-DD HH24:MI'""")
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#------------------------------------------------------------------------------
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# create_schema(): drop and create the demo table, and add a row
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def create_schema():
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with pool.acquire() as connection:
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with connection.cursor() as cursor:
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cursor.execute("""
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begin
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begin
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execute immediate 'drop table demo';
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exception when others then
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if sqlcode <> -942 then
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raise;
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end if;
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end;
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execute immediate 'create table demo (
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id number generated by default as identity,
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username varchar2(40))';
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insert into demo (username) values ('chris');
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commit;
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end;""")
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#------------------------------------------------------------------------------
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app = Flask(__name__)
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# Display a welcome message on the 'home' page
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@app.route('/')
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def index():
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return "Welcome to the demo app"
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# Add a new username
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#
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# The new user's id is generated by the database and returned in the OUT bind
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# variable 'idbv'.
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@app.route('/post/<string:username>')
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def post(username):
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with pool.acquire() as connection:
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with connection.cursor() as cursor:
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connection.autocommit = True
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idbv = cursor.var(int)
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cursor.execute("""
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insert into demo (username)
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values (:unbv)
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returning id into :idbv""", [username, idbv])
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return f'Inserted {username} with id {idbv.getvalue()[0]}'
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# Show the username for a given id
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@app.route('/user/<int:id>')
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def show_username(id):
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with pool.acquire() as connection:
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with connection.cursor() as cursor:
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cursor.execute("select username from demo where id = :idbv", [id])
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r = cursor.fetchone()
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return r[0] if r is not None else "Unknown user id"
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#------------------------------------------------------------------------------
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if __name__ == '__main__':
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# Start a pool of connections
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pool = start_pool()
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# Create a demo table
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create_schema()
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# Start a webserver
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app.run(port=port)
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