Add Lesson 4 files for combining message passing techniques

lesson-4-message-passing-in-production/combining-message-passing-techniques-solution/README.md

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+# Flask Starter
+This is a bare-bones Flask application that showcases how simple it can be to set up a REST API. It also serves as a starter template for users to begin experimenting with writing their own REST API endpoints.
+
+Flask applications can look very different depending on how they are structured and implemented. This application is built to have the minimum number of dependencies to run.
+
+## Running the app
+1. Install Flask: `pip install Flask kafka-python`
+2. Run the app: `flask run`
+
+The application should be available at `localhost:5000`.

lesson-4-message-passing-in-production/combining-message-passing-techniques-solution/app.py

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+import json
+
+from kafka import KafkaProducer
+from flask import Flask, jsonify, request, g, Response
+
+from .services import retrieve_orders, create_order
+
+app = Flask(__name__)
+
+@app.before_request
+def before_request():
+    # Set up a Kafka producer
+    TOPIC_NAME = 'items'
+    KAFKA_SERVER = 'localhost:9092'
+    producer = KafkaProducer(bootstrap_servers=KAFKA_SERVER)
+    # Setting Kafka to g enables us to use this
+    # in other parts of our application
+    g.kafka_producer = producer
+
+
+@app.route('/health')
+def health():
+    return jsonify({'response': 'Hello World!'})
+
+
+@app.route('/api/orders/computers', methods=['GET', 'POST'])
+def computers():
+    if request.method == 'GET':
+        return jsonify(retrieve_orders())
+    elif request.method == 'POST':
+        request_body = request.json
+        result = create_order(request_body)
+        return Response(status=202)
+    else:
+        raise Exception('Unsupported HTTP request type.')
+
+
+@app.route('/api/v2/orders/computers', methods=['GET', 'POST'])
+def computers():
+    if request.method == 'GET':
+        return jsonify(retrieve_orders())
+    elif request.method == 'POST':
+        request_body = request.json
+        result = create_order(request_body)
+        return Response(status=202)
+    else:
+        raise Exception('Unsupported HTTP request type.')
+
+
+
+if __name__ == '__main__':
+    app.run()

lesson-4-message-passing-in-production/combining-message-passing-techniques-solution/enums.py

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+from enum import Enum
+
+class Status(Enum):
+    Queued = 'Queued'
+    Processing = 'Processing'
+    Completed = 'Completed'
+    Failed = 'Failed'

lesson-4-message-passing-in-production/combining-message-passing-techniques-solution/requirements.txt

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+Flask
+kafka-python

lesson-4-message-passing-in-production/combining-message-passing-techniques-solution/services.py

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+import json
+from .app import g
+from .enums import Status
+
+
+def create_order(order_data):
+    """
+    This is a stubbed method of retrieving a resource. It doesn't actually do anything.
+    """
+    # Turn order_data into a binary string for Kafka
+    kafka_data = json.dumps(order_data).encode()
+    # Kafka producer has already been set up in Flask context
+    kafka_producer = g.kafka_producer
+    kafka_producer.send("items", kafka_data)
+
+
+def retrieve_orders():
+    """
+    This is a stubbed method of retrieving multiple resources. It doesn't actually do anything.
+    """
+    return [
+        {
+            "id": "1",
+            "status": Status.Queued.value,
+            "created_at": "2020-10-16T10:31:10.969696",
+            "created_by": "USER14",
+            "equipment": [
+                "KEYBOARD", "MOUSE"
+            ]
+        },
+        {
+            "id": "2",
+            "status": Status.Queued.value,
+            "created_at": "2020-10-16T10:29:10.969696",
+            "created_by": "USER15",
+            "equipment": [
+                "KEYBOARD", "WEBCAM"
+            ]
+        }
+    ]

lesson-4-message-passing-in-production/flask-kafka-starter/README.md

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+# Flask Starter
+This is a bare-bones Flask application that showcases how simple it can be to set up a REST API. It also serves as a starter template for users to begin experimenting with writing their own REST API endpoints.
+
+Flask applications can look very different depending on how they are structured and implemented. This application is built to have the minimum number of dependencies to run.
+
+## Running the app
+1. Install Flask: `pip install Flask kafka-python`
+2. Run the app: `flask run`
+
+The application should be available at `localhost:5000`.

lesson-4-message-passing-in-production/flask-kafka-starter/app.py

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+import json
+
+from kafka import KafkaProducer
+from flask import Flask, jsonify, request, g, Response
+
+from .services import retrieve_orders, create_order
+
+app = Flask(__name__)
+
+@app.before_request
+def before_request():
+    # Set up a Kafka producer
+    TOPIC_NAME = 'items'
+    KAFKA_SERVER = 'localhost:9092'
+    producer = KafkaProducer(bootstrap_servers=KAFKA_SERVER)
+    # Setting Kafka to g enables us to use this
+    # in other parts of our application
+    g.kafka_producer = producer
+
+
+@app.route('/health')
+def health():
+    return jsonify({'response': 'Hello World!'})
+
+
+@app.route('/api/orders/computers', methods=['GET', 'POST'])
+def computers():
+    if request.method == 'GET':
+        return jsonify(retrieve_orders())
+    elif request.method == 'POST':
+        request_body = request.json
+        result = create_order(request_body)
+        return Response(status=202)
+    else:
+        raise Exception('Unsupported HTTP request type.')
+
+
+if __name__ == '__main__':
+    app.run()

lesson-4-message-passing-in-production/flask-kafka-starter/enums.py

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+from enum import Enum
+
+class Status(Enum):
+    Queued = 'Queued'
+    Processing = 'Processing'
+    Completed = 'Completed'
+    Failed = 'Failed'

lesson-4-message-passing-in-production/flask-kafka-starter/requirements.txt

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+Flask
+kafka-python

lesson-4-message-passing-in-production/flask-kafka-starter/services.py

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+import json
+from .app import g
+from .enums import Status
+
+
+def create_order(order_data):
+    """
+    This is a stubbed method of retrieving a resource. It doesn't actually do anything.
+    """
+    # Turn order_data into a binary string for Kafka
+    # kafka_data = json.dumps(order_data).encode()
+    # Kafka producer has already been set up in Flask context
+    # kafka_producer = g.kafka_producer
+    # TODO: send the data using kafka_producer using .send()
+    kafka_data = json.dumps(order_data).encode()
+    kafka_producer = g.kafka_producer
+    kafka_producer.send("items", kafka_data)
+
+
+def retrieve_orders():
+    """
+    This is a stubbed method of retrieving multiple resources. It doesn't actually do anything.
+    """
+    return [
+        {
+            "id": "1",
+            "status": Status.Queued.value,
+            "created_at": "2020-10-16T10:31:10.969696",
+            "created_by": "USER14",
+            "equipment": [
+                "KEYBOARD", "MOUSE"
+            ]
+        },
+        {
+            "id": "2",
+            "status": Status.Queued.value,
+            "created_at": "2020-10-16T10:29:10.969696",
+            "created_by": "USER15",
+            "equipment": [
+                "KEYBOARD", "WEBCAM"
+            ]
+        }
+    ]