CS4300 - Flask Template

This Flask app template is intended to get you started with your project and launch it on Heroku, and assumes no prior experience with web development (but some patience).

We recommend you start with the quick start guide FIRST and then read the Flask Template Walk-through section. Some may find the additional information about AWS and KUBERNETES deployment to be useful, but those are not vital to getting your project working.

If you have any questions, do not hesitate to ask the TAs or come to OH. In this README, we will include an overview section with information on the flask app architecture and a step-by-step guide to loading up your app in dev and production (in Heroku) with instructions for (optional) EC2/EB add-ons coming soon. This README was originally written by Ilan Filonenko with help from Joseph Antonakakis.

Table of Contents

Quick Start Guide

Flask Template Walk-through

Google Cloud Deployment

AWS Deployment

Quickstart Guide

1. Cloning the repository from Git

git clone https://github.com/CornellNLP/CS4300_Flask_template.git
cd CS4300_Flask_template

2. Setting up your virtual environment

We assume by now all of you have seen and used virtualenv, but if not, go here to install and for dead-simple usage go here

# Create a new python3 virtualenv named venv.
virtualenv -p python3 venv
# Activate the environment
source venv/bin/activate # (or the equivalent in Windows)

# Install all requirements
pip install -r requirements.txt

(For Mac users, you may encounter an ERROR: Failed building wheel for greenlet. This can be fixed with xcode-select --install.)

An aside note: In the above example, we created a virtualenv for a python3 environment. You will have python3.7.6 installed by default as we have used that version for assignments. This is what we will use for the application as well.

NOTE: While you should be able to install these requirements in the virtualenv you used for the assignments, we advise using a fresh virtualenv so you can be sure that your virtualenv's installed packages and your repository's requirements.txt match exactly. This will be important when you add new dependencies.

To add any dependencies for future development just do this:

pip install <MODULE_NAME>
pip freeze > requirements.txt

3. Ensuring environment variables are present

We will be using environment variables to manage configurations for our application. This is a good practice to hide settings you want to keep out of your public code like passwords or machine-specific configurations. We will maintain all of our environment variables in a file, and we will populate our environment with these settings before running the app. We have provided you with starter environment files but remember to add them to your .gitignore if you add sensitive information to them.

Unix - MacOSx, Linux, Git Bash on Windows

• Your environment variables are stored in a file called .env
• To set your environment:

source .env

• To add a variable to your file, add a line to .env with the syntax:

export MY_VARIABLE=SOME_VALUE

Windows Cmd Prompt

• Your environment variables are stored in a file called env.bat
• To set your environment:

call env.bat

• To add a variable to your file, add a line to env.bat with the syntax:

SET MY_VARIABLE=SOME_VALUE

autoenv (Optional: Unix systems or Windows Git Bash only)

If you desire, you can set up a tool called autoenv so that every time you enter the directory, all environment variables are set immediately. This is handy for hiding configurations that you want to keep out of your public code, like passwords for example. autoenv is already installed with the requirements you installed above. NOTE: This utility is not critical to the project, it's just nice to have. To set up autoenv:

# Override cd by adding this to your .[?]rc file ([?] = bash, zsh, fish, etc),
# according to your current CLI. I'll use bash in this example:
echo "source `which activate.sh`" >> ~/.bashrc

# Reload your shell
source ~/.bashrc

# Check to see you have a .env file that exists and 
# has sets the appropriate APP_SETTINGS and DATABASE_URL variables;
# else create a new file with those variables
cat .env

# This command should produce something non-empty (specifically: config.DevelopmentConfig) if your autoenv is correctly configured
echo $APP_SETTINGS

# Reactivate the environment because you just reloaded the shell
source venv/bin/activate

If you are having issues getting autoenv working (echo $APP_SETTINGS returns empty), try running source .env from the root directory of your forked repository. This will manually set the environment variables. You will have to do this each each time you reopen the terminal.

4. Optional: Setting up Postgres Backend (if interested in Postgres)

You may either install the PostgresApp if you are using a Mac here or follow the detailed installation guide to install it manually on your Mac or Windows. Then run the following code after Postgres server is up: NOTE: you may find the need to "initialize" a new database through the Postgres App or through the initdb command before you are able to proceed with the following commands.

# Enter postgres command line interface
$ psql
# Create your database which I will call my_app_db in this example, but you can change accordingly
CREATE DATABASE my_app_db;
# Quit out
\q

The above creates the actual database that will be used for this application and the name of the database is my_app_db which you can change, but make sure to change the .env file and in your production app accordingly which I will talk about lower in this guide.

5. Check to see if app runs fine by running in localhost:

python3 app.py

If you encounter a KeyError: 'APP_SETTINGS', try running source .env (Mac) or call env.bat (Windows) again. At this point the app should be running on http://localhost:5000/. Navigate to that URL in your browser.

6. Push to heroku

We have included a Procfile (process file) that leverages gunicorn (which you can read more about here) for deployment.

To set up heroku and push this app to it, you must do the following:

1. Install the heroku-cli following the installation instructions found here and create an account with heroku. After that, run the following commands to push to your heroku app into deployment using git from your command line!

# Update heroku-cli to its latest version
$ heroku update

# Login with your heroku credentials
$ heroku auth:login
Enter your Heroku credentials:
# You will be directed to a browser login page

# This create logic might be deprecated so
# navigate to Heroku Dashboard and create app manually
$ heroku create <YOUR_WEBSITE_NAME>

# Note you will have had to commit any changes you've made
# since cloning this template in order to push to heroku
$ git push heroku master

2. Now, go to your Heroku dashboard and find your app. This will probably be here: https://dashboard.heroku.com/apps/<YOUR_WEBSITE_NAME>.

3. You need to modify your environment variables (remember your .env?) by navigating to https://dashboard.heroku.com/apps/<YOUR_WEBSITE_NAME>/settings, clicking Reveal Config Vars and in the left box below DATABASE_URL write: APP_SETTINGS and in the box to the right write: config.ProductionConfig.

(In essence you are writing export APP_SETTINGS=config.ProductionConfig in .env using Heroku's UI. You can also do this from the heroku-cli using the heroku config:edit command.)

4. You lastly will run: heroku ps:scale web=1. You may now navigate to https://<YOUR_WEBSITE_NAME>.herokuapp.com and see your app in production. From now on, you can continue to push to Heroku and have a easy and well-managed dev flow into production. Hooray!

You can check out the example herokuapp: here

Where to go from here?

At some point you will need to fork this repo and name your repo cs4300sp2020-##### with your netids substituting the #####.

To begin customizing this boilerplate webapp to actually do something interesting with your search queries, you should look at modifying the app/irsystem/controllers/search_controller.py file where you can see the params we are passing into the rendered view.

If you plan on reading no further than this, please at least skim the section An Indepth Flask App Walk-through, it will provide you a good background on how to interact and modify this template.

---

An Indepth Flask App Walk-through

This will overview Flask development operations for setting up a new project with an emphasis on the Model-View-Controller design pattern. This guide will be utilizing PostgreSQL to drive persistent storage on the backend.

Some of the first few sections will mirror the steps you took in the quickstart guide but will be more in-depth.

Organization

A Flask app has some utility scripts at the top-level, and has a modular organization when defining any sort of functionality. Dividing up a Flask app into modules allows one to separate resource / logic concerns.

The utility scripts at the top level include the following:

config.py # describes different environments that app runs in
manage.py # holds functionality for migrating your database (changing its schema)
app.py    # runs the app on a port

The entire functional backend of a Flask app is housed in a parent module called app. You can create this by creating a directory app and populating it with an __init__.py file. Then, inside that app directory, you can create modules that describe the resources of your app. These modules should be as de-coupled and reusable as possible. For example, let's say I need a bunch of user authentication logic described by a couple of endpoints and helper functions. These might be useful in another Flask app and can be comfortably separated from other functionality. As a result, I would make a module called accounts inside my app directory. Each module (including app) should also have a templates directory if you plan on adding any HTML views to your app.

Template

The use of templates here is specifically for the purpose of mimicking the structure of an MVC application. In this application, I have separated the system into two separate templates: accounts and irsystem, since some of you might need to leverage the database for user/session log flow so you would only use the irsystem template. The irsystem is what you will be manipulating for the purposes of your information retrevial. If you look at the file search_controller.py you can see that we are rendering the view with data being passed in. This data will the results from your IR system which you will customize accordingly. You may make more models/controllers for organization purposes.

Database Setup

If you followed the quickstart guide, you should now have set up postgres.

Rather than writing raw-SQL for this application, I have chosen to utilize SQLAlchemy (specifically, Flask-SQLAlchemy) as a database Object-Relational-Model (ORM, for short). In addition, for the purposes of serialization (turning these database entities into organized JSONs that we can send over the wire) and deserialization (turning a JSON into a entity once again), I have chosen to use Marshmallow (specifically, marshmallow-SQLAlchemy).

Several modules are needed to completely integrate Postgres into a Flask app, but several of these modules are co-dependent on one another. I have included all of these in the requirements.txt file, these modules include: flask-migrate marshmallow-sqlalchemy psycopg2.

The migration script, manage.py will be used to capture changes you make over time to the schemas of your various models.
This script will not work out of the gate and refers to components we have not yet defined in our app, but I will describe these below:

import os
from flask_script import Manager
from flask_migrate import Migrate, MigrateCommand
from app import app, db

migrate = Migrate(app, db)
manager = Manager(app)

manager.add_command("db", MigrateCommand)

if __name__ == "__main__":
  manager.run()

In the above, app refers to the module we created above in the File Organization section. db refers to our reference to the database connection that we have yet to define in the app module.

This script can be used in the following way to migrate your database, on changing your models:

# Initialize migrations
python manage.py db init
# Create a migration
python manage.py db migrate
# Apply it to the DB
python manage.py db upgrade

You should run these methods after having the .env setup because it requires the APP_SETTINGS and DATABASE_URL to be defined. If you get errors in this section as a result of key-errors for APP_SETTINGS and DATABASE_URL go to the Environment Variables section and make sure to delete the migrations folder that is already created with running python manage.py db init

Configuration Setup

Now that we have setup our database and have handled our manage.py script, we can create our config.py script, which involves the database and various other configuration information specific to Flask. This file will be used in our initialization of the Flask app in the app module in the near future.

An example of a config.py file that is used in the project looks like this:

import os
basedir = os.path.abspath(os.path.dirname(__file__))

# Different environments for the app to run in

class Config(object):
  DEBUG = False
  CSRF_ENABLED = True
  CSRF_SESSION_KEY = "secret"
  SECRET_KEY = "not_this"
  SQLALCHEMY_DATABASE_URI = os.environ['DATABASE_URL']

class ProductionConfig(Config):
  DEBUG = False

class StagingConfig(Config):
  DEVELOPMENT = True
  DEBUG = True

class DevelopmentConfig(Config):
  DEVELOPMENT = True
  DEBUG = True

class TestingConfig(Config):
  TESTING = True

The above defines several classes used to instantiate configuration objects in the creation of a Flask app. Let's go through some of the variables:

• DEBUG indicates whether or not debug stack traces will be logged by the server.
• CSRF_ENABLED, CSRF_SESSION_KEY, and SECRET_KEY all relate to Cross-Site-Request-Forgery, which you can read more about here.
• SQLALCHEMY_DATABASE_URI refers to the database URL (a server running your database). In the above example, I refer to an environment variable 'DATABASE_URL'. I will be discussing environment variables in the next section, so stay tuned.

Environment Variables

Environment variables allow one to specify credentials like a sensitive database URL, API keys, secret keys, etc. These variables can be manually export-ed in the shell that you are running your server in, but that is a clunky approach. The tool autoenv solves this problem.

autoenv allows for environment variable loading on cd-ing into the base directory of the project. Follow the following command line arguments to install autoenv:

# Install the package from pip
pip install autoenv
# Override cd by adding this to your .?rc file (? = bash, zsh, fish, etc), I'll use
echo "source `which activate.sh`" >> ~/.?rc
# Reload your shell
source ~/.?rc
# Make a .env file to hold variables
touch .env

As mentioned in the above code, your .env file will be where you hold variables, and will look something like this:

# Set the environment type of the app (see config.py)
export APP_SETTINGS=config.DevelopmentConfig
# Set the DB url to a local database for development
export DATABASE_URL=postgresql://localhost/my_app_db

As you can see above in the example, I reference a specific configuration class (DevelopmentConfig), meaning I plan on working in my development environment. I also have my database URL. Both of which are used heavily in the app. In local mode you will be maniuplating the .env file but in production you will be manipulating the Config Variables in your Heroku instance or you will modify the .env files in your AWS EC2/EB application.

NOTE: Now, be sure to gitignore your .env file.

Flask App Setup

Up until now, we haven't been able to run our server.

The configurations of the Flask app are contained in ./app/__init__.py. The file should look like this:

# Gevent needed for sockets
from gevent import monkey
monkey.patch_all()

# Imports
import os
from flask import Flask, render_template
from flask_sqlalchemy import SQLAlchemy
from flask_socketio import SocketIO

# Configure app
socketio = SocketIO()
app = Flask(__name__)
app.config.from_object(os.environ["APP_SETTINGS"])
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = True

# DB
db = SQLAlchemy(app)

# Import + Register Blueprints
# WORKFLOW:
# from app.blue import blue as blue_print
# app.register_blueprint(blue_print)

# Initialize app w/SocketIO
socketio.init_app(app)

# HTTP error handling
@app.errorhandler(404)
def not_found(error):
  return render_template("404.html"), 404

Let's unpack this file piece by piece. The top initializes Gevent, a coroutine-based Python networking library for Socket.IO (a very useful socket library useful in adding real-time sockets to your app). The next section imports several libraries, initializes our Flask app, set our app up with the configurations from the appropriate config.py class, creates the db connection pool, bootstraps Socket.IO to our Flask app, and sets the 404 error page that the app should present on not finding a resource. NOTE: the comments regarding registering a "blueprint" will be where we register our sub-modules with our main, parent Flask app.

Since we have involved Socket.IO and Gevent, you wil see it in requirements.txt

Finally, in order to actually start our server, you will run the app.py script. This script can be placed at the root of our project:

from app import app, socketio

if __name__ == "__main__":
  print("Flask app running at http://0.0.0.0:5000")
  socketio.run(app, host="0.0.0.0", port=5000)

Now, at the root of your application, you can run:

python app.py

Your server is now running!

NOTE: If you get issues regarding APP_SETTINGS or DATABASE_URL, you should ensure your .env is setup properly, and you should cd out of and back into your project root.

That's it, for now...

This marks the end of project configuration for a well-constructed Flask app following MVC. However, for additional development-related advice regarding project setup, keep reading.

Accounts Blueprint

Now we will be diving into writing Models and Controllers for an accounts blueprint that will serve as reusable users-sessions module that can be added to any application desiring a sign-up system. We make some short-cuts along the way in order to increase this guide's brevity, while still providing meaningful sample code and explanations for the different components of the system.

We must create our module within app, such that it contains the following structure:

.
├── __init__.py
├── controllers
│   ├── __init__.py
│   ├── sessions_controller.py
│   └── users_controller.py
└── models
    ├── __init__.py
    ├── session.py
    └── user.py

Let's start with ./app/accounts/__init__.py. This file contains a couple of lines of information specifying the Flask Blueprint information of this module, as well import controllers:

from flask import Blueprint

# Define a Blueprint for this module (mchat)
accounts = Blueprint('accounts', __name__, url_prefix='/accounts')

# Import all controllers
from controllers.users_controller import *
from controllers.sessions_controller import *

In addition, register your new blueprint in ./app/__init__.py by changing the lines:

# Import + Register Blueprints
# WORKFLOW:
# from app.blue import blue as blue_print
# app.register_blueprint(blue_print)

to:

# Import + Register Blueprints
from app.accounts import accounts as accounts
app.register_blueprint(accounts)

The Models

The models created will correspond, field-by-field, to the database tables that will be setup as a result of you running the series of migration commands listed above in the Database Setup section.

Base Model and Imports

Before looking into the Base model (the abstract model parent class that all models will extend from) we will look at Werkzeug, included in your requirements.txt, which is a module that is required to hash user-passwords (you never want to store passwords in plain-text). We should, technically, salt the passwords too, but given that this is just an example, I'll leave that detail to your implementation.

In ./models/__init__.py, (accessible to the entire models module) we should write the following:

from app import db # Grab the db from the top-level app
from marshmallow_sqlalchemy import ModelSchema # Needed for serialization in each model
from werkzeug import check_password_hash, generate_password_hash # Hashing
import hashlib # For session_token generation (session-based auth. flow)

class Base(db.Model):
  """Base PostgreSQL model"""
  __abstract__ = True
  id         = db.Column(db.Integer, primary_key =True)
  created_at = db.Column(db.DateTime, default    =db.func.current_timestamp())
  updated_at = db.Column(db.DateTime, default    =db.func.current_timestamp())

The above imports modules and objects necessary for use in your models, as well as defines a Base model class that every model should extend to inherit the book-keeping and necessary fields, id, created_at, and updated_at.

User Model

The User model in ./models/user.py will consist of the following:

from . import *

class User(Base):
  __tablename__ = 'users'

  email           = db.Column(db.String(128), nullable =False, unique =True)
  fname           = db.Column(db.String(128), nullable =False)
  lname           = db.Column(db.String(128), nullable =False)
  password_digest = db.Column(db.String(192), nullable =False)

  def __init__(self, ** kwargs):
    self.email           = kwargs.get('email', None)
    self.fname           = kwargs.get('fname', None)
    self.lname           = kwargs.get('lname', None)
    self.password_digest = generate_password_hash(kwargs.get('password'), None)

  def __repr__(self):
    return str(self.__dict__)


class UserSchema(ModelSchema):
  class Meta:
    model = User

The above is pretty self-explanatory. It outlines several db fields, declares a constructor, defines a default string-based representation of the User model, and declares a UserSchema class that will be used to serialize and deserialize the User model to / from JSON.

Session Model

The Session model in ./models/session.py will consist of the following:

from . import *

class Session(Base):
  __tablename__ = 'sessions'

  user_id       = db.Column(db.Integer, db.ForeignKey('users.id'), unique =True, index =True)
  session_token = db.Column(db.String(40))
  update_token  = db.Column(db.String(40))
  expires_at    = db.Column(db.DateTime)

  def __init__(self, ** kwargs):
    user = kwargs.get('user', None)
    if user is None:
      raise Exception() # Shouldn't be the case

    self.user_id       = user.id
    self.session_token = self.urlsafe_base_64()
    self.update_token  = self.urlsafe_base_64()
    self.expires_at    = datetime.datetime.now() + datetime.timedelta(days=7)

  def __repr__(self):
    return str(self.__dict__)

  def urlsafe_base_64(self):
    return hashlib.sha1(os.urandom(64)).hexdigest()


class SessionSchema(ModelSchema):
  class Meta:
    model = Session

As we can see, the session model will belong to the user, and be part of a token-based authentication flow. Everything in the above code is self-explanatory, and serves as an example session implementation.

Exposing Models to the App

We must import our models into our app in order to have them be exposed to our manage.py script responsible for migrating our db to match our programmatic schema. In ./controllers/__int__.py, I added the following (we'll throw in the imports while we're at it):

from functools import wraps
from flask import request, jsonify, abort
import os

# Import module models
from app.accounts.models.user import *
from app.accounts.models.session import *

For other models and controllers you add with database connection you can safely run the following in the root of your project to migrate your database:

# Initialize migrations
python manage.py db init
# Create a migration
python manage.py db migrate
# Apply it to the DB
python manage.py db upgrade

Now if you connect to your Postgres database, you should see two new tables, users and sessions! The migration also creates an index on foreign-key user_id in sessions, for fast access of sessions by their owning user's id.

That's it for models.

Additional Features Added

In addition to the flask application I have added some useful encoding features that can be leveraged by your application. Because we leverage numpy arrays all the time when calculating doc-by-vocab matricies I have included some encoding techniques for 2D numpy matricies which I will review soon.

Recommendations:

If you are using Heroku or AWS EC2/EB you have a limited number of RAM and in-memory space to store your json data. As such it is recommended that you leverage SVDs on your doc-by-vocab matricies to reduce the dimensionality of your data. Because text-data is ALWAYS dimensionally reducible you should leverage the techniques covered in class in your application. To have fast responses and limited logic I would recommend to pre-process all of your data structures and numpy arrays and store them in some storage system. Two storage systems that I would recommend include: Amazon S3 and Redis.

Amazon S3

After setting up an AWS account and buying some space on your S3 server you can easily put data into your S3 bucket with this simple command:

curl --verbose -A "<PASSWORD>" -T <FILE_NAME.EXTENSION> https://s3.amazonaws.com/<YOUR_LOCATION>

I would recommend storing all your datastructures in json files and pushing those jsons to S3 in your pre-processing stages, and pulling from S3 at run-time be leveraging the encoding techniques that I have included in app.irsystem.models.helpers.

class NumpyEncoder(json.JSONEncoder):

    def default(self, obj):
        """If input object is an ndarray it will be converted into a dict
        holding dtype, shape and the data, base64 encoded.
        """
        if isinstance(obj, np.ndarray):
            if obj.flags['C_CONTIGUOUS']:
                obj_data = obj.data
            else:
                cont_obj = np.ascontiguousarray(obj)
                assert(cont_obj.flags['C_CONTIGUOUS'])
                obj_data = cont_obj.data
            data_b64 = base64.b64encode(obj_data)
            return dict(__ndarray__=data_b64,
                        dtype=str(obj.dtype),
                        shape=obj.shape)
        # Let the base class default method raise the TypeError
        return json.JSONEncoder(self, obj)

def json_numpy_obj_hook(dct):
    """Decodes a previously encoded numpy ndarray with proper shape and dtype.
    :param dct: (dict) json encoded ndarray
    :return: (ndarray) if input was an encoded ndarray
    """
    if isinstance(dct, dict) and '__ndarray__' in dct:
        data = base64.b64decode(dct['__ndarray__'])
        return np.frombuffer(data, dct['dtype']).reshape(dct['shape'])
    return dct

I will show you how to use these encoding techniques below:

from app.irsystem.models.helpers import NumpyEncoder as NumpyEncoder
from app.irsystem.models.helpers import json_numpy_obj_hook
# Dump numpy array into a json file
json.dump(NUMPY_ARRAY_NAME, open('NUMPY_ARRAY_NAME.json', 'w'), cls=NumpyEncoder)
# Read numpy array from a json file (where FILE_NAME is an S3 location or local file)
NUMPY_ARRAY_NAME = json.load(FILE_NAME, object_hook=json_numpy_obj_hook, encoding='utf8')

Redis

Redis is an in-memory data structure store, used as a database, cache and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs and geospatial indexes with radius queries. Redis has built-in replication, Lua scripting, LRU eviction, transactions and different levels of on-disk persistence, and provides high availability via Redis Sentinel and automatic partitioning with Redis Cluster. In this application I will be leveraging the python bindings provided by redis-py which allow for me to interact with the available redis cluster using python. You can read more about Redis and its useful for ML applications via its in-memory nature here. You can setup your redis cluster using either the Ansible script provided here or the Kubernetes Helm chart provided here. The importance of using the above setup logic is to include the redis-ml support for matrix manipulation. After deploying your cluster to your appropriate port (i.e. 127.0.0.1:6379). Check if redis-server is up by running and getting PONG as a result, hehe :)

$ redis-cli ping
PONG

You can modify the Redis DB by running:

$ redis-cli
redis 127.0.0.1:6379> ping
PONG
redis 127.0.0.1:6379> set mykey somevalue
OK
redis 127.0.0.1:6379> get mykey
"somevalue"

At this point in time you are able to use the RedisConnector provided by CuAppDev. To create a Redis connection to the redis cluster you will execute the following:

from appdev.connectors import MySQLConnector, RedisConnector
redis = RedisConnector('entry_checkpoint')

The normal TCP socket based connection will be available by calling:

connection = redis._single_connect()

And if you want to leverage connection pools to manage connections to the redis server with finer grain control and client side sharding you can use this by calling:

pool = redis._connect_pool(5) # for max 5 connections

You can now run the following cmomands to store a numpy matrix into Redis

# Create RedisConn Class
redis = RedisConnector('entry_checkpoint')
# Grab TCP Connection
connection = redis._single_connect()
# Store key information that we will be using to define the shape of the numpy array
redis.dump_matrix(connection,"example_numpy",input_numpy_array)
# Or store a dictionary
entry_redis_key = 'training_entries'
redis.dump_dictionary(connection, {entry_redis_key: entries})
# Now you can get the matrix or dictionary by running the following
entries = redis.get_matrix(get_matrix,"example_numpy")
entries_dict = redis.get_dictionary(connection, entry_redis_key)

You should leverage the pipeline() feature if you are going to be calling more than one (non 2D numpy array) value from Redis. Pipelines are a subclass of the base Redis class that provide support for buffering multiple commands to the server in a single request. They can be used to dramatically increase the performance of groups of commands by reducing the number of back-and-forth TCP packets between the client and server. In the example above there is only 1 in the array, but you can get any number of values you want, in order of requested, given the keys.

MySQL

(IN PROGRESS) But you may use MySQL for the cool connector available here

Google Cloud (DB, Docker, Kubernetes)

Prerequisites

There a few things you need to do to get started:

1. Apply the Google Cloud Credits to your account. Follow the directions on Piazza to do this
2. Create a new project. Open up the Google Cloud Platform Console and click on the project dropdown on the top menu bar (it will either say "No Project" or the name of your current project). Select "New Project", choose a name, and click "Create".
3. Install the command line tools. You will need to install kubectl here and gcloud here for this (see the Quickstarts on the left).
4. Install Docker here.

Setting up your Database

You can setup a database quickly by doing the following:

1. Open up the Google Cloud Platform Console
2. Go to Storage > SQL
3. Create Instance
4. Create a PostgreSQL Instance

And everything else is self-explanatory. Upon creation it will give you an instance link that you will use for the DATABASE_URL.

Dockerizing your App

Docker is a program that is used to run an app in a container (essentially a virtualized operating system). It is useful because it allows you to setup your app in one environment, your container, then deploy it anywhere. A Docker container is configured using a Dockerfile, such as the one below (taken from /kubernetes):

# Read from Ubuntu Base Image
FROM python:3.7.6
RUN mkdir -p /service
# Copy over all the files of interest
ADD app /service/app
ADD app.py /service/app.py
ADD config.py /service/config.py
ADD manage.py /service/manage.py
ADD requirements.txt /service/requirements.txt
WORKDIR /service/
RUN pip install -r requirements.txt
CMD python -u app.py $APP_SETTINGS $DATABASE_URL

This Dockerfile is using an existing Ubuntu-based container with Python installed, adding your app files, then installing your app dependencies. You most likely won't need to modify this further for your app, but this should give a good idea of how you can add other files to your container and execute other setup commands.

Now let's walk through pushing this Docker image:

> pwd
/Users/hunruh/CS4300_Flask_template
> ls
Procfile         app              config.py        kubernetes       requirements.txt vagrant
README.md        app.py           config.pyc       manage.py        runtime.txt      venv
> docker build -t <YOUR DOCKER USERNAME>/flask-template:v1 -f kubernetes/Dockerfile .

You will replace <YOUR DOCKER USERNAME> with your own Docker username so that you can push the image to your public Docker Hub account. The image name is flask-template which you can also replace and :v1 is the image tag (you can change this to :latest if you only want the most recent version).

Now that you have the Docker image built, push it to a public repo on Docker Hub

> docker push <YOUR DOCKER USERNAME>/flask-template:v1

Now we have a publicly accessible Docker image. You can update this image as your app changes by re-building and re-pushing (you may find it helpful to change the image tag for new versions, or a cached version of your image may be used rather than the latest from Docker Hub). How do we test this locally? You need to run a docker-compose.yml script to bring the image up. A sample script is provided in kubernetes/docker-compose.yml, and can be run with the following:

# Note we are now in the /kubernetes subdirectory
> pwd
/Users/hunruh/CS4300_Flask_template/kubernetes
> docker-compose up
kubernetes_flask_1 is up-to-date
Attaching to kubernetes_flask_1
flask_1  | Flask app running at http://0.0.0.0:5000

You can now navigate to http://0.0.0.0:5000 to see if your app is running correctly.

Getting Ready for Kubernetes

Your app is configured and ready to go, but we need to deploy to Kubernetes and put it behind a load-balancer to make it publicly accessible. Do the following:

1. Open up the Google Cloud Platform Console
2. Go to Compute > Kubernetes Engine
3. Click Create Cluster
4. Name the cluster and set a description.
5. Set Zone to us-east4-a.
6. Set Number of Nodes to 1
7. Leave Cluster Version to be 1.11.7-gke.12 (default).
8. Leave Machine Type with 1 vCPU and 3.75 GB memory
9. Click Create

Now wait for the cluster to come up. When you see a green check mark next to the cluster name then you are ready to continue.

Configure kubectl to connect to your cluster:

1. Click Connect
2. Copy and paste the command shown in the dialog into the terminal on your computer. It should look something like gcloud container clusters get-credentials <YOUR CLUSTER NAME> --zone us-east4-a --project <YOUR PROJECT ID>

If everything is working right, you should be able to run the following:

# Configure your connection to your cluster
> gcloud container clusters get-credentials <YOUR CLUSTER NAME> --zone us-east4-a --project <YOUR PROJECT ID>
Fetching cluster endpoint and auth data.
kubeconfig entry generated for cluster-1.

# Check the nodes - we should only see 1
> kubectl get nodes
NAME                                       STATUS    ROLES     AGE       VERSION
gke-cluster-1-default-pool-a7da8d2d-2g8c   Ready     <none>    1m        v1.11.7-gke.12

# Check pods running - none are running yet
> kubectl get pods
No resources found.

Now we want to deploy a Kubernetes pod with the Docker image we configured. This is defined by a .yml file like the one found in kubernetes/run-deployment.yml. You should be able to use this file as-is, with one exception: make sure to replace <YOUR DOCKER USERNAME>/flask-template:v1 with your Docker image name and the most recent tag you want to use. Feel free to customize anything else you need.

We are levaraging a Deployment here so that we can update the app in real-time via the version tag on the image (this useful for swapping between prototypes). A/B swaps are handled by Kubernetes, so there will be no down-time in your app. If you find your app is getting heavy traffic and needs to be scaled up, you can increase the number of replicas, but for now it is only 1 (that should be enough - note that the more resources you use, the more it will cost).

Deploying to Kubernetes

Now run the following to deploy your app:

# We will now launch this pod
> kubectl create -f kubernetes/run-deployment.yml
deployment "flask" created

# List pods
> kubectl get pods
NAME      READY     STATUS              RESTARTS   AGE
flask     0/1       ContainerCreating   0          18s

# Wait about a minute
> kubectl get pods
NAME      READY     STATUS    RESTARTS   AGE
flask     1/1       Running   0          1m

> kubectl get deployments
NAME      DESIRED   CURRENT   UP-TO-DATE   AVAILABLE   AGE
flask     1         1         1            1           1m

# See which services are running - it will only be Kubernetes Master
> kubectl get svc
NAME         TYPE        CLUSTER-IP    EXTERNAL-IP   PORT(S)   AGE
kubernetes   ClusterIP   10.27.240.1   <none>        443/TCP   11m

# Deploy the service for our pod: flask
> kubectl expose deployment flask --type=LoadBalancer
service "flask" exposed

> kubectl get svc
NAME         TYPE           CLUSTER-IP      EXTERNAL-IP   PORT(S)          AGE
flask        LoadBalancer   10.27.248.200   <pending>     5000:31380/TCP   9s
kubernetes   ClusterIP      10.27.240.1     <none>        443/TCP          11m

# Wait a minute
> kubectl get svc
NAME         TYPE           CLUSTER-IP      EXTERNAL-IP    PORT(S)          AGE
flask        LoadBalancer   10.27.248.200   35.188.251.150 5000:31380/TCP   46s
kubernetes   ClusterIP      10.27.240.1     <none>         443/TCP          12m

Now if we go to 35.188.251.150:5000 (replace the address with the EXTERNAL-IP provided) you should be able to see your app.

Updating your app in real time

Now that you have your workflow setup, suppose you want to update your app for the next prototype. Update your Docker image by building a new version:

# Note the v2 instead of the v1.. showing an updated version
> docker build -t <YOUR DOCKER USERNAME>/flask-template:v2 -f kubernetes/Dockerfile .
> docker push <YOUR DOCKER USERNAME>/flask-template:v2

Then update the deployment (only the deployment... the service is still running fine) live with the following command:

# This will take you to a vi portal which will
# allow you to edit the run-deployment.yml file.
# You simply need to update the version number on the image config and BOOM
> kubectl edit deployment flask
...

Enjoy your Kubernetes-deployed app!!

Deploy to EC2 Quick

Welcome to the world of automation. Get ready to be blown away :)

To get started we must install Vagrant here

With vagrant installed: check success of installation with vagrant help

Next, you will install ansible which can be done with this command: sudo pip install ansible

Now you are ready to have some fun! Follow these steps exactly to deploy and test your app:

$ git clone https://github.com/CornellNLP/CS4300_Flask_template.git
$ cd CS4300_Flask_template
$ cd vagrant
$ vagrant up
$ vagrant provision
...
TASK [Make sure nginx is running] **********************************************
ok: [default] => {"changed": false, "name": "nginx", "state": "started"}

RUNNING HANDLER [restart nginx] ************************************************
changed: [default] => {"changed": true, "name": "nginx", "state": "started"}

PLAY RECAP *********************************************************************
default                    : ok=16   changed=12   unreachable=0    failed=0

Now navigate to http://192.168.33.10/ and you will see the app loaded up!

Let's deploy this AWS now!

First step is to launch an EC2 instance (on the Oregon Availability Zone)

This EC2 instance should be using Ubuntu Server 18.04 LTS (HVM), SSD Volume Type as an AMI. This AMI will be the same type of OS that we used for our VM.

I would recommend that you choose the t2.micro, which is a small, free tier-eligible instance type.

Make your security group one with these configs:

Ports	Protocol	Source
80	tcp	0.0.0.0/0, ::/0
22	tcp	0.0.0.0/0, ::/0
443	tcp	0.0.0.0/0, ::/0

After, launching download the the key-pair and name it a4keypair.

Place the a4keypair.pem inside the vagrant folder.

Ensure, that your vagrant folder looks like this:

$ ls
Vagrantfile     a4keypair.pem   ansible.cfg     cs.nginx.j2     hosts           site.yml        start.sh.j2       systemd.service.j2
$ chmod 700 a4keypair.pem

Your next step will be to take the public IP found when clicking on your instance in the EC2 terminal under: IPv4 Public IP and putting that into the hosts file. So the hosts file should look like this, with <YOUR_PUBLIC_IP> being replaced by that IPv4 Public IP value:

[webservers]
 <YOUR_PUBLIC_IP> ansible_ssh_user=ubuntu ansible_python_interpreter=/usr/bin/python3

Insure that you had the the private key by running ssh-keygen:

$ ssh-keygen
enerating public/private rsa key pair.
Enter file in which to save the key (/Users/<YOUR_USERNAME>/.ssh/id_rsa):
Enter passphrase (empty for no passphrase):
Enter same passphrase again:
Your identification has been saved in /Users/<YOUR_USERNAME>/.ssh/id_rsa.
Your public key has been saved in /Users/<YOUR_USERNAME>/.ssh/id_rsa.pub.
...

After this you are ready to push have an automated script push to your EC2 instance, just execute this:

$ ansible -m ping webservers --private-key=a4keypair.pem --inventory=hosts --user=ubuntu
<YOUR_PUBLIC_IP> | SUCCESS => {
    "changed": false,
    "ping": "pong"
}
$ ansible-playbook -v site.yml
...
PLAY [Starting a Simple Flask App] ******************************************************************************************************************************************************************

TASK [Gathering Facts] ******************************************************************************************************************************************************************************
ok: [<YOUR_PUBLIC_IP>]
...
TASK [Make sure nginx is running] *******************************************************************************************************************************************************************
ok: [<YOUR_PUBLIC_IP>] => {"changed": false, "name": "nginx", "state": "started"}

PLAY RECAP ******************************************************************************************************************************************************************************************
<YOUR_PUBLIC_IP>             : ok=15   changed=2    unreachable=0    failed=0

Boom! You are done :) How easy was that!