Each lab will consist of a small problem and details of  how to proceed. Each lab is intended to give every student hands-on experience with the core technologies utilized during the course.  A student may concentrate, as a team member, on one technology over another for the final project, but labs are designed to give each and every student exposure to all the technologies that come into play.  You need to submit labs to the TAs for grading--see submission instructions below.  Generally, unless otherwise specified, you will have one week to complete each assigned lab.

See the syllabus for information on grading.  Turning in lab assignments on time is required, without exception, and all late deliveries will be penalized, regardless of cause.  Submit your assignments to the subversion repository according to the directions on the syllabus page.

For steps 1-3, you will be working in Java.  For Step 4 below, you may write these solutions in either Java or C++ or Python or whatever language you wish...your choice, as long as it's supported under RabbitMQ.

Lab 3   Due: 5:00 pm, Monday, November 9, 2020

Problem 1:  Playing With Docker and RabbitMQ: 

BACKGROUND:

WHAT YOU NEED TO DO:

For this third lab, we are going to code a microservice that runs RabbitMQ and two client microservices (each running in its own container) that pass messages over the queue.  You will work through a couple of the very fine examples provided on the RabbitMQ website and then you will each write a Request/Response RPC producer/consumer yourselves.

STEP 1:

Get RabbitMQ in a Docker Container (RABBITMQ)

First, make sure docker is running in your environment.  Next, get down a dockerized RabbitMQ:

On Linux (or VirtualBox VM):

docker run -d --hostname my-wabbit --name MyWabbit rabbitmq:3-management

On the Mac:

docker run -d --hostname my-wabbit --name MyWabbit -p 15672:15672 -p 5672:5672 rabbitmq:3-management

In this latter MAC command you have mapped the management console port to 15672 on the mac AND you have mapped port 5672 on the MAC.  THIS is the port that rabbitmq server listens on by default for new connections: 

"For RabbitMQ to accept client connections, it needs to bind to one or more interfaces and listen on (protocol-specific) ports. The interfaces are configured using the rabbit.tcp_listeners config option. By default, RabbitMQ will listen on port 5672 on all available interfaces".  Cf.: https://www.rabbitmq.com/networking.html.  Note the Linux version of docker will map ports for you.

docker exec -it MyWabbit /bin/bash

update the software:

apt-get update
apt-get install -y procps
apt-get install -y vim
apt-get install -y net-tools
apt-get install -y openssh-client

NOTE:  DO NOT install default-jdk as you will not need it...and there are issues.

Stay in your container...

STEP 2:

Compile Send.java:
javac Send.java

Then execute "java Send" from MsgProducer container

root@msgproducer:/src/HelloWorld# java Send
 [x] Sent 'Hello World!'

Then, in your MyWabbit container, verify that your queue has one message on it (the "hello" queue has 1 message):

root@my-wabbit:/# rabbitmqctl list_queues
Listing queues
hello    1

Use the RabbitMQ management console running in a browser in your VirtualBox VM and hit:  http://172.17.0.2:15672/. Of course substitute the IP address of your MyWabbit container in the above URL.  On a Mac, enter instead http://localhost:15672/ because of the defined port mapping.

If you are asked to log into RabbitMQ, the default username is "guest" and the default password is "guest".

Examine the message that was sent under the Queues Tab under "Get Messages":



Finally, use docker save to save your container to a new image.

On a Mac, enter instead http://localhost:15672/ because of the defined port mapping.
 
Examine the message that was sent under the Queues Tab and verify that the hello queue as 0 Messages under the Ready column.



Next, start two MsgConsumers in two seperate terminal windows and a single MsgProducer in a third terminal window.  Set your CLASSPATH in each instance of the containers.  In each MsgConsumer container, run java Recv.  These programs will block.  Then, in the MsgProducer container, run java Send over and over again.  Notice what is happening with each of the two MsgConsumers.  You are witnessing Point-to-Point messaging with a round-robin algorithm.

Finally, use docker save to save your container to a new image.

References:

You may find the following references helpful (in addition to the links from previous labs):

The docker page for RabbitMQ
RabbitMQ Documentation
RabbitMQ Clients (Java, C++, Python, Ruby, Spring, etc.)
RabbitMQ Java Javadocs
Ubuntu package commands

General Docker Tutorial Links

Submitting:

Use the folder named "lab_3" in your Subversion repository. See the syllabus for more info about submission using Subversion.  Upload your Lab 3 MsgProducer and MsgConsumer and MyWabbit tarballs (using docker export) to this repo.  gzip each tarball before submitting.  Please include a README text file that contains any instructions for the TAs to assist with grading, including how to run your containers, and any other helpful hints you can provide.