MPCS_51205-Lab

Lab 4 Details for MPCS 51205

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.

You may write this solution in Java.

Lab 3 Due: 5:00 pm, Monday, November 13, 2023

Problem 1: Playing With Multiple Dockerized Microservices and MongoDB:

BACKGROUND:

Like all programming problems, learning a new technology is not an exercise in reading but rather and exercise in typing. This lab is designed to give you hands-on experience in (a) running multiple dockerized microservices that communicate both synchronously and asynchronously with each other and finally write data to a MongoDB database. You will generally find the References section below helpful in addition to the required and recommended reading. When we talk about "Docker", we are talking specifically about the Stable Community Edition of Docker, which is the version we will be using in this class. The Stable Community Edition provides the basic container engine and built-in orchestration, networking, and security.

WHAT YOU NEED TO DO:

STEP 1:

For this fourth lab, we are going to run a prototype that consists of four distinct microservices. This prototype consists of:

1. A dockerized Apache Tomcat web server microservice named WebServer running ubuntu that will serve up a web page and backing jsp and Java servlet that will prompt the user to add a new user to the system. This web page is for adding new users only and is strictly no frills. A field for a username, and a second field for a password, and an "Confirm New User" button that, when clicked, does no error checking and sends the new user request (over synchronous RMI from the servlet) to the UserManagement microservice, which has an RMI Server listening for remote calls.

2. A dockerized UserManagement microservice running ubuntu that hosts an RMI Server that listens for new user requests from the WebServer's servlet-based RMI client. A synchronous RMI client running in the servlet on the WebServer is used to communicate new user requests to the RMI server running on UserManagement.

3. The RMI server running on UserManagement receives the new user request and forwards that request asynchronously to a queue running in a dockerized RabbitMQ microservice called MyWabbit.

4. A dockerized LoggingService, based on a docker MongoDB image will be listening/subscribed to the MyWabbit's "new user" queue, and upon every incoming message (about a new user to add), will write that new user's information out to a new MongoDB document. Note that the purpose of the MongoDB database is not to store new user information, but to provide a document store for log messages from the system.

The big picture here is this:

kahuna

These steps will involve running several different docker containers and installing software inside them. Details are below. After downloading and installing the prototype in STEPS 2-5, get the prototype running (there will be a few code and environment changes you will need to make) and examine the code carefully and observe how it executes.

First, make sure docker is running either on your laptop (Option I from the first lab) or in your VM (Option II from the first lab).

STEP 2:

Get Tomcat working in a Docker Container (WebService microservice)

First, get down the Apache Tomcat app server into a new container. Do this by executing the following docker command:

docker run -di --hostname tomcat --name WebServer -p 8080:8080 tomcat:8.0

Once you have that container down (and verify it is running), obtain a bash shell in that container by running docker exec into the container. Once you are in your WebService container, install some software in the container. Install:

apt-get update
apt-get install vim
apt-get install net-tools
apt-get install openssh-client
apt-get install default-jdk

Once you have the software installed, let's hit the Tomcat default web page at http://localhost:8080/index.jsp. Bookmark this page. Then navigate to http://localhost:8080/docs/index.html. Browse around the documentation a bit. Next, browse over to http://localhost:8080/examples, and go into the Servlets examples, and Execute the Hello World servlet. Back up two levels and go into the jsp examples at http://localhost:8080/examples/jsp/. Try the Numberguess and Calendar examples under the JSP 1.2 Examples heading. Take a look at the source code for these examples (the "Source" link to the right of "Execute").

Now, we need to modify the setup a bit. Namely, we need to set you up as an admin so you can run the tomcat manager. Use vi to edit the file in your tomcat container:   /usr/local/tomcat/conf/tomcat-users.xml. Note that Tomcat's configuration files are located in the /usr/local/tomcat/conf directory. Edit the file and at the very end (right above the closing </tomcat-users> tag and below the --> comment end"), add these two lines:

<role rolename="admin"/>
<user username="admin" password="admin" roles="manager-gui,manager-status,manager-script,manager-jmx,admin-gui"/>

Save the file and exit vi. Now, hop out of your container's bash shell and have docker restart the Tomcat server:

docker restart WebServer

Now, exec a bash shell back into WebServer. Go back to your browser and hit http://localhost:8080/manager/html (yes, it's slash html and not .html) and when prompted, log in as "admin/admin". You should now be in the Tomcat Web Application Manager. You will become intimate with this.

Now for some sample software. cd to the following directory: /usr/local/tomcat/webapps. Do an ls and look at the directories there. This is where Tomcat stores web applications, one of which you're about to install. Now, using scp from within your WebServer container, type

scp userid@linux.cs.uchicago.edu:/home/mark/pub/51205/src.labs/lab4/tomcat.starter.kit.tgz .
[enter your userid and password on the cluster]

Now, untar that tarball under the /usr/local/tomcat/webapps subdirectory. Do an "ls" again. You should see a new mpcs subdirectory. Execute:

root@tomcat:/usr/local/tomcat/webapps/# find mpcs

You will see a number of files under the mpcs directory, including a WEB-INF subdirectory, a jsps subdirectory, and a WEB-INF/classes subdirectory. Note especially the mpcs/WEB-INF/web.xml file, as it is the key to the kingdom as far as Tomcat applications are concerned.

Now, go back to your Tomcat Web Application Manager, and refresh the page. Scroll down and you will see a new application Path for mpcs. Look for options over to the right including Stop, Reload, and Undeploy. Click on Reload now.

Finally, navigate to this page: http://localhost:8080/mpcs/jsps/starter.kit.html. You should see a tidy little web page allowing you to enter a New Username and a New Password by clicking on a button called "Confirm New User". Resist the urge to click on the button quite yet.

Now, in your shell cd over to /usr/local/tomcat/webapps/mpcs/WEB-INF/classes directory and execute the command ". set.classpath.sh" (make sure you have a space after the initial period before the command...). Then echo out your $CLASSPATH variable:

root@tomcat:/usr/local/tomcat/webapps/mpcs/WEB-INF/classes# . set.classpath.sh
root@tomcat:/usr/local/tomcat/webapps/mpcs/WEB-INF/classes# echo $CLASSPATH
/usr/local/tomcat/lib/servlet-api.jar:/opt/rabbitmq-java-client/amqp-client-4.0.2.jar:/opt/rabbitmq-java-client/slf4j-api-1.7.21.jar:/opt/rabbitmq-java-client/slf4j-simple-1.7.22.jar:.

Don't worry that you do not have the rabbitmq jars. That's ok. They are there in case you wish to use asynchronous communication to talk to RabbitMQ. Our little prototype does not do that.

Now, do an "ls" on the classes directory. You will find several java files, along with several .class files. Using vi, hop into HelloWorldServlet.java and take a look at its contents. Then hop out without saving (":q! [Enter]").

Now, let's compile our java source files. In the classes directory, execute:

root@tomcat:/usr/local/tomcat/webapps/mpcs/WEB-INF/classes# javac *.java

STEP 3:

Get RabbitMQ working in a Docker Container (MyWabbit microservice)

You will reuse your MyWabbit microservice from the previous lab. If you have removed it or it has otherwise suffered irreperable damage, you may create another one. Simply refer back to the instructions for Lab 3, STEP 1, in order to do that. (You may need to docker rm your current MyWabbit container). You will need to have net-tools installed in your RabbitMQ container.   See STEP 4 below on how to apt-get net-tools.

One thing. docker exec into the container and execute ifconfig and write down the IP address reported for your MyWabbit container. It will be something like "173.17.0.3". You will need to modify some source code in both the UserManagement and LoggingService containers with that IP address.

The good news is after all you had to do for STEP 2 above, this is all you have to do for STEP 3.

STEP 4:

Get ubuntu working in a Docker Container (UserManagement microservice)

First, get down the Ubuntu:18.04 container. Do this by executing the following command:

docker run -di --hostname usrmgr --name UserManagement ubuntu:18.04

Once you have that container down (and running), obtain a bash shell in that container by running docker exec into the container. Once you are in your UserManagement container, docker exec into the container and install some software in the container:

apt-get update
apt-get install -y vim
apt-get install -y net-tools
apt-get install -y openssh-client
apt-get install -y openjdk-8-jdk-headless

cd to / and create a subdirectory called "/src/RMI" (mkdir -p /src/RMI) and change to the /src directory. Next, download ~mark/pub/51205/src/lab4/UserManagement.tgz and copy it into your container and untar the contents into your RMI subdirectory.

scp userid@linux.cs.uchicago.edu:/home/mark/pub/51205/src.labs/lab4/UserManagement.tgz .
[enter your userid and password on the cluster]

Now, untar the tarball:

root@usrmgr:/src/# tar xzvf UserManagement.tgz
root@usrmgr:/src/# find .
root@usrmgr:/src/# cd RMI

Now, set your classpath (you will need to do this everytime you log in, or add the call to your .bashrc file):

root@usrmgr:/src/# . set.classpath.sh
root@usrmgr:/src/# echo $CLASSPATH
/opt/rabbitmq-java-client/amqp-client-4.0.2.jar:/opt/rabbitmq-java-client/slf4j-api-1.7.21.jar:/opt/rabbitmq-java-client/slf4j-simple-1.7.22.jar:/opt/mongo-java-client/mongo-java-driver-2.13.3.jar:.

Now, we need to get your jar balls down and into your /opt directory, which right now should be empty.

Install the RabbitMQ client tarball (as you did in lab 3) into your UserManagement container under the /opt directory:

root@usrmgr:/# cd /opt
root@usrmgr:/# scp userid@linux.cs.uchicago.edu:/home/mark/pub/51205/src.labs/rabbitmq-java-client.tgz .
[enter your password on the cluster]

root@usrmgr:/# ls rabbit*
rabbitmq-java-client.tgz

root@usrmgr:/opt# tar xzvf rabbitmq-java-client.tgz

root@usrmgr:/opt# find rabbitmq-java-client/
rabbitmq-java-client/
rabbitmq-java-client/slf4j-simple-1.7.22.jar
rabbitmq-java-client/amqp-client-4.0.2.jar
rabbitmq-java-client/slf4j-api-1.7.21.jar

You will not need to install the mongodb jarball in UserManagement.

This container will serve as your "UserManagement" microservice container for this lab.

Now, change to your /src/RMI directory. Type "javac *.java" to compile everything. Then, execute:

root@usrmgr:/src/RMI# javac *.java

Examine the java source code beginning with RMIServer.java carefully. Make sure you understand what is going on.

You should not see any errors. Fix any issues.

STEP 5:

Get MongoDB working in a Docker Container (LoggingService microservice)

First, get down the MongoDB database Server into a new container. Do this by executing the following docker command:

docker run --hostname mongodb --name LoggingService -p 28017:28017 -p 27017:27017 -e MONGODB_PASS="password" -d mongo:3.4-xenial

Read the MongoDB page on the docker hub to make sure you understand the implication of these port assignments. Once you have that container down (and running), obtain a bash shell in that container by running docker exec into the container. Once you are in your LoggingService container, install some software in the container:

apt-get update
apt-get install vim
apt-get install net-tools
apt-get install openssh-client
apt-get install default-jdk

Next, you'll need to install both the mongodb and rabbitmq java client jarballs:

root@mongodb/# cd /opt
root@mongodb:/opt# scp userid@linux.cs.uchicago.edu:/stage/classes/archive/2019/fall/51205-1/libs/* .
[enter your password on the cluster]

root@mongodb:/opt# ls rabbit*
rabbitmq-java-client.tgz

root@:/opt# tar xzvf rabbitmq-java-client.tgz

root@mongodb:/opt# find rabbitmq-java-client/
rabbitmq-java-client/
rabbitmq-java-client/slf4j-simple-1.7.22.jar
rabbitmq-java-client/amqp-client-4.0.2.jar
rabbitmq-java-client/slf4j-api-1.7.21.jar

root@mongodb:/opt# ls mongo*
mongo-java-client.tgz

root@mongodb:/opt# tar xzvf mongo-java-client.tgz

root@mongodb:/opt# find mongo-java-client
/opt/mongo-java-client/
/opt/mongo-java-client/mongo-java-driver-2.13.3.jar
/opt/mongo-java-client/gson-2.6.2.jar
/opt/mongo-java-client/._mongo-java-driver-2.13.3.jar
/opt/mongo-java-client/._gson-2.6.2.jar

Now, we need to download our java source code.

Now, cd to the highest-level "/" directory.

root@mongodb:/# scp userid@linux.cs.uchicago.edu:/home/mark/pub/51205/src.labs/lab4/mongodb.src.tgz .
[enter your password on the cluster]

Now, untar that tarball:

root@mongodb:/opt# tar xzvf mongodb.src.tgz

Then type "cd /src". Now, set your classpath (you will need to do this everytime you log in, or add the call to your .bashrc file):

root@mongodb:/src/# . set.classpath.sh
root@mongodb:/src/# echo $CLASSPATH
/opt/rabbitmq-java-client/amqp-client-4.0.2.jar:/opt/rabbitmq-java-client/slf4j-api-1.7.21.jar:/opt/rabbitmq-java-client/slf4j-simple-1.7.22.jar:/opt/mongo-java-client/mongo-java-driver-2.13.3.jar::.

Type "javac *.java" to compile everything.

root@mongodb:/src# javac *.java

Examine the java source code beginning with Recv.java carefully. Make sure you understand what is going on.

You should not see any errors. Fix any issues.

STEP 6:

Run it all.

WebServer startup:

The WebServer should still be running. You may need to update the IP address of UserManagement in the servlet code. Get into your UserManagement container and type "ifconfig" and note the inet addr for eth0. It should be something like "172.17.0.4". Edit the code located at /usr/local/tomcat/webapps/mpcs/WEB-INF/classes/HelloWorldServlet.java. Search for 172.17. Then change that to the correct IP address for the RMIServer running in UserManagement. Makd sure that that address matches your actual IP address of UserManagement. Save the file and recompile.

Now, go back to your Tomcat Web Application Manager, and refresh the page. Scroll down and you will see mpcs. Click on Reload.

UserManagement startup:

Now run the server:

root@usrmgr:/src/RMI# java RMIServer

LoggingService startup:

Now run the server:

root@mongodb:/src# java Recv

NOTE: Should you see a connection refused error in the logs, then drop the mark.queue, and re-run java Recv.

RabbitMQ startup:

Of course, MyWabbit should already be running, if it's not, start it again (docker start MyWabbit).

Docker exec into your MyWabbit container (if you're not already there). You will need to create a new queue. For the source code to work, the queue needs to be named "mark.queue". Create the queue from the RabbitMQ Management Console. Make the queue a direct exchange and make it durable. Do not set it for auto delete and do not make it internal. You did something similar in Lab 3. Refer to Lab 3 STEP 5 if you have any questions on how to do this.

STEP 7:

Execute.

The WebServer should still be running. Go to the webapp with the create new user page (http://localhost:8080/mpcs/jsps/starter.kit.html) and enter a new user and a new user password. Click on the button.

Then, navigate to your LoggingService terminal, and see if you have new output. You should see a lot of MONGODB:... output, but the last line should be "Message To Log: {...}" and you should see that the newPassword is set to the password you entered and the newUserName field is set to the new user name you entered.

Hit control-C (^-C) to exit out of the Recv program, and then run mongo:

root@mongodb:/src# mongo

At the ">" prompt in mongo, type the following commands:
> show dbs
> use loggingService
> show collections
> db.logging.find().pretty()
> quit()

And you should see the log for the new user you created in mongodb, as a new document.

Note that the default logging location for Tomcat is /usr/local/tomcat/logs/*. You will find that the log calls (for debugging purposes...not your logging calls to the LoggingService) in the servlet go to a file called "localhost.2019.11.14.log" (your mileage may vary with the name, but you can grep the logs directory for "context.log"), and the log calls inside the servlet code look like this:

       ...
       context.log("in doPost");
       context.log("in Preparing to call RMI");

        String userName = request.getParameter( "user_name" );
       context.log("userName is: "+userName);
        String userPassword = request.getParameter( "user_password" );
       context.log("userPassword is: "+userPassword);
       ...

A sample of the output of this logging looks like this:

14-Nov-2019 23:19:05.540 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log in doGet
14-Nov-2019 23:19:05.540 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log calling doPost
14-Nov-2019 23:19:05.540 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log in doPost
14-Nov-2019 23:19:05.540 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log in Preparing to call RMI
14-Nov-2019 23:19:05.541 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log userName is: joe
14-Nov-2019 23:19:05.541 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log userPassword is: blow
14-Nov-2019 23:19:05.541 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log in doPost Preparing to call RabbitMQ
14-Nov-2019 23:19:05.555 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log in doPost Preparing to call RMI
14-Nov-2019 23:19:05.557 INFO [http-apr-8080-exec-17] org.apache.catalina.core.ApplicationContext.log RemoteInterface and registery set up with address and port

You can add context.log() calls to enhance your understanding of what the servlet code is doing. The other programs (RMIServer and Recv) all log straight to the console.

STEP 8:

Review.

It might behoove you to now go back "down" through the code, from the tomcat servlet through the UserManagement service through the LoggingService code, and make sure you understand what all is taking place here.

STEP 9:

Your turn (only if you want).

Now, the servlet really doesn't know whether the user and password were actually successfully logged in the mongodb database. Frankly, in the real world, that's perfectly fine, and the cost of doing business "fire and forget". But what if the servlet did want to know that the data was successfully logged before it returned from doPost? Let's imagine that we do care.

Now, create a Request/Reply queue in the Rabbit management console (one each) and have the servlet create a CorrelationID (you can hard-code this CorrelationID) after it has made the call to the RMI server in UserManagement, and send the CorrelationID via the Request queue from doPost().

Then, inside the LoggingService code, after successfully writing the data to the mongodb database, have the LoggingService retrieve the CorrelationID from the Request queue and send it back to the servlet via the Reply queue, which will be listening to the Reply queue.

Once the servlet receives the CorrelationID back from the LoggingService via the Reply queue, the servlet can then consider its work "done". Create both the Request and Reply queues as durable.

Hints: You will need to add the amqp jar to the Tomcat's lib directory and restart the Tomcat WebServer container.

References:

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

Ubuntu package commands
The docker page for MongoDB
MongoDB Documentation Home Page
Microservices resources at MongoDB

General Docker Tutorial Links

Docker Cheat Sheet

Submission:

For Labs:

Each student should submit their LabN files and any supporting materials to the repo. Please include a README text file that contains any instructions or additional details for the TAs to assist with grading.

Setup:

When you open the invitation URL in a browser tab, you will have to complete the following steps:

Github may ask you to grant permission for GitHub Classroom to have access to your GitHub account. If you are asked this question, you should say yes and grant access to Github Classroom.

You must click “Accept this assignment” or your repository will not actually be created. Do not skip this step!

If you run into any issues, please ask for help.

Use the folder named "lab_4" in your Subversion repository (create it if necessary). Upload your Lab 4 microservice tarballs to this repo. Please include a README text file that contains any instructions for the TAs to assist with grading, and design notes are often the most useful thing you can provide. We do not usually need any info on how to compile your code unless your code layout is arcane.