Add week 5 materials

materials/05-indirect-comm/seminar/work_queues/docker-compose.yml

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+version: "3"
+
+services:
+    rabbitmq:
+        image: rabbitmq:3-management
+        hostname: "rabbitmq"
+        ports:
+            - "15672:15672"
+            - "5672:5672"
+    new_task:
+        build: 
+            context: new_task
+    worker1:
+        build: 
+            context: worker
+
+    worker2:
+        build:
+            context: worker

materials/05-indirect-comm/seminar/work_queues/new_task/Dockerfile

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+FROM python:3.8
+
+RUN mkdir /root/app/
+WORKDIR /root/app/
+
+RUN pip install pika
+
+COPY . .
+
+ENV PYTHONPATH "${PYTHONPATH}:/root/app/"
+EXPOSE 5000
+
+CMD ["bash", "-c", "while ! curl -s rabbitmq:15672 > /dev/null; do echo waiting for rabbitmq; sleep 3; done; python -u new_task.py"]

materials/05-indirect-comm/seminar/work_queues/new_task/new_task.py

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+#!/usr/bin/env python
+import pika
+import sys
+import time
+
+
+if __name__ == '__main__':
+    connection = pika.BlockingConnection(pika.ConnectionParameters(host='rabbitmq', port=5672))
+    channel = connection.channel()
+
+    channel.queue_declare(queue='task_queue', durable=True)
+    channel.confirm_delivery()
+
+    for message in ['first message.', 'second message..', 'third message...']:
+        while True:
+            try:
+                channel.basic_publish(
+                    exchange='',
+                    routing_key='task_queue',
+                    body=message,
+                    properties=pika.BasicProperties(
+                        delivery_mode=2,  # make message persistent. Marking messages as persistent doesn't fully guarantee that a message won't be lost. Although it tells RabbitMQ to save the message to disk, there is still a short time window when RabbitMQ has accepted a message and hasn't saved it yet. Also, RabbitMQ doesn't do fsync(2) for every message
+                ))
+            except Exception as e:
+                print("retransmit")
+                time.sleep(1)
+            else:
+                break
+        print(" [x] Sent %r" % message)
+    connection.close()

materials/05-indirect-comm/seminar/work_queues/worker/Dockerfile

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+FROM python:3.8
+
+RUN mkdir /root/app/
+WORKDIR /root/app/
+
+RUN pip install pika
+
+COPY . .
+
+ENV PYTHONPATH "${PYTHONPATH}:/root/app/"
+EXPOSE 5000
+
+CMD ["bash", "-c", "while ! curl -s rabbitmq:15672 > /dev/null; do echo waiting for rabbitmq; sleep 3; done; python -u worker.py"]

materials/05-indirect-comm/seminar/work_queues/worker/worker.py

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+#!/usr/bin/env python
+import pika
+import time
+
+
+if __name__ == '__main__':
+    connection = pika.BlockingConnection(pika.ConnectionParameters(host='rabbitmq', port=5672))
+    channel = connection.channel()
+
+    channel.queue_declare(queue='task_queue', durable=True)  # to make sure that the queue will survive a RabbitMQ node restart
+    print(' [*] Waiting for messages.')
+
+
+    def callback(ch, method, properties, body):
+        print(" [x] Received %r" % body.decode())
+        time.sleep(body.count(b'.'))
+        print(" [x] Done")
+        ch.basic_ack(delivery_tag=method.delivery_tag)  # Send ack
+
+
+    channel.basic_qos(prefetch_count=1)  # This uses the basic.qos protocol method to tell RabbitMQ not to give more than one message to a worker at a time
+    channel.basic_consume(queue='task_queue', on_message_callback=callback)
+
+    channel.start_consuming()