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[Intro music]

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Hello and welcome to this demo.

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In this demo, we're going to look at the example-voting-app.

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The example-voting-app is available in GitHub under the dockersamples

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repository, and it is available at example-voting-app.

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I will add a link to this in the resources section.

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In this demo, we're going to look at the architecture of

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this. We're going to look at the source code a little bit,

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understand how it's put together, and we will try and deploy

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this application using Docker.

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But to start with, we're just going to deposit the application

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with docker run just to make it really simple.

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And then in the next demo, we'll try to use Docker Compose,

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and going forward, we'll use Docker stack and services to

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deploy it on Swarm.

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So as a first step, let's try and just understand the application.

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So the source code is available on GitHub, and you can see

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basic documentation here.

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If you look at the architecture, as we discussed in the lecture,

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you have a voting-app which is based in Python, and then

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you have a redis messaging system.

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The vote is cast, and it goes to the worker, which is based

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on .NET, and then the vote is updated in a Postgres database,

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and then finally, the result is displayed in a Node.js based

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result web application.

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Out of these two of the components are Redis and Postgres,

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so we don't have to worry about that.

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The three other components are the applications that we developed.

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So there are three folders in this code repository.

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[No audio]

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We'll first look at the voting-app, so if you click on the

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vote directory, you will be able to see the source code of

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it. And it's a Python based application.

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So you have the app.py with the Python code in it.

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If you open the Python code, it's a flask based application.

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It's a very simple application.

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It has a post and a get request.

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The GET request sent an index.html which shows the actual

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web page where a user can cast a vote.

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And when the user cast a vote, it comes to this POST section,

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and that is where it establishes connectivity to Redis and

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tries to store the vote information in Redis.

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So that's all that this particular voting-application is.

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And one thing to take note here is the host that it tries

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to, it tries to connect to a host named redis.

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Okay, now, alongside the code, we also have the Dockerfile,

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so it creates it from a python
:2.7-alpine image and then

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set the working directory to app, installs the Python requirements.

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[No audio]

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The next step is where it copies the application code into

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the app folder, and finally the Entrypoint for the application.

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Next, we will take a look at the worker.

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So go to the worker folder, and the source code of the application

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is under the main/java/worker folder, and there is a Worker.java.

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If you look at this code, this is .NET based application.

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So at the top it tries to connect to the Redis and the Postgres

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database. And there's a while loop where it waits for the

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votes from redis.

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And whenever a vote is cast and it's available in redis,

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it takes that vote and updates the table in the Postgres

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database. If you're interested, go through and take a look

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at the remainder of the code.

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We will then look at the Dockerfile.

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So the Dockerfile is based on Microsoft dotnet SDK, and that

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is where it adds the source code of the application to the

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worker folder and finally updates the command required to

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start the worker.

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Next, we will look at the result-app, which is based in Node.js.

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So that is under the result folder and open the server.js.

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This is an express based server, and you can see the source code for that.

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And all this does is it establishes a connectivity to the

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Postgres database.

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And as you can see, the Postgres database, that host that

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tries to connect to is db. So that's the host name that it tries

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to connect to, and then it reads the database and reads the

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values from the database and displays that on the UI.

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[No audio]

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And if you look at the Dockerfile for that, it starts from

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the Docker image, starts from a Node.js slim image, and then

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adds the package.json, which has the dependencies, runs npm

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install to install those dependencies, copies the source code

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over, and finally specifies the node server.js command that

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is to be run when the application starts.

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And then there are also, in the source code repository

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there are also some docker-compose and docker-stack files.

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But we will not look at that right now.

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We will be creating those ourselves.

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So we will just ignore that.

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So what we're going to do now is we'll just go try and deploy

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this application ourselves with Docker.

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But the first thing that we need to do is build these images,

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because we know that the Redis and Postgres databases already

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have images available on the Docker Hub, but the three others

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are the applications that we are developing.

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So we do not have images built for those, so we'll have to build them.

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So I'm going to first clone the source code repository

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to my local system.

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So I will do a git clone and then paste the address, and

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that will clone the source.

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It is cloned it into example-voting-app.

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And when I go into example-voting-app, I have all the code

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that we just walked through.

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Okay, so we will start with deploying the voting-app.

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For that, we need to create a Docker image for the voting-app.

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[No audio]

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So we will go into the vote directory and we look at

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the Dockerfile. The Dockerfile looks intact.

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So we're just going to go ahead and build the Docker image

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by running the docker build command, and we will tag it with

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a name voting-app.

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Okay, so the Docker image is built.

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If you run the docker images command, you can see that it

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has the voting-app image built.

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So now that I have the voting-app image built, I can run

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a Container by running the docker run voting-app command,

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and I'm going to publish a Port 5000 to 80.

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So the, the Container,

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the voting-app Container runs on Port 80, and I'm going to

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map that to Port 5000 on my host so that I can access it from a browser.

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So it looks like the Container is running.

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So I'm going to try and open a browser and go to the address

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with Port 5000, and I can see that the web application is

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displayed, and I can see two options to cast my vote, CATS and DOGS.

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Now, if I try to cast a vote by clicking on one of the button,

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you can see it tries to, it takes a while, and after a while, it fails.

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And I can now see that there's an internal server error.

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It says the server encountered and internal error and was

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unable to complete your request.

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If I go back and look at the logs, I see that it failed at

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the line redis.rpush.

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So basically it's unable to establish a connectivity to the

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Redis, obviously, because we haven't run a Redis instance.

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[No audio]

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So what we're going to do now is I'm just going to kill that

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instance, and I will first start a redis Container.

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So I will run an instance of redis, and I will name it redis

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[No audio]

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So it's pulling down the redis image and it's run an instance of Redis.

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I forgot to run it in the background, so I'll stop that and run it again.

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The -d for the detach option.

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Okay, so when I tried that, it failed again because I had

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already run it without the detached option.

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So it already created a Container with the name redis.

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And I'm trying to create another Container with the same

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name, so it's preventing me from doing that.

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So I'll have to delete that the previously created Containers.

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So I'm going to run a docker rm command to delete the previously

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created Container, and I'll run the same command again to

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start a new instance of redis.

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So I now have a redis instance running.

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I'm now going to start an instance of my voting-app.

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So I will run the docker run command with voting-app, and

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I will publish the Port 5000.

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I will also this time add a link to the redis server.

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So I'm running a voting-app and and added a link using the

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--link option and specified redis as we discussed in the

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lecture. Okay, so it's running now.

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I'm back to my web portal, and when I now try to cast a vote,

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you see that it goes successfully and I get a tick mark back.

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Now, this is because my Container I was now able to run establish

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a connectivity to Redis.

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So now we have successfully deployed Redis as well as the

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voting-application.

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We will now proceed to the worker and for the worker prerequisite

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is to have a Postgres database.

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So we will first deploy a postgres database instance.

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I'm not really sure what is the version of Postgres that

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this application requires.

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So I'm going to go into one of the files here.

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For example, if I go into the docker-stack file or a docker-compose file,

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I should be able to find the image that they

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used. So it's image 9.4.

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So I'm just going to use that here.

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I will name the instance db.

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And so later on, I can use that to create a link.

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And now, as you can see, it's running, the Postgres database

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is now started, and it's running successfully.

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I forgot to run in the background, so I'm just going to kill

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that runs in the background.

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Okay.

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I hit the issue again about the duplicate name.

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So I'm just going to delete the one that I created using

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the docker rm command.

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And I'm going to rerun the Postgres database in the detached

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mode. So I now have the Postgres database running.

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So if I do a docker ps, I see that there are three Containers

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running. One is my voting-app, one is my redis, and the third

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one is the postgres database.

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I can now go ahead and deploy the worker.

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So first I'll have to build the worker.

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So if I go to the worker directory and I can see the contents

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of the Dockerfile, make sure it's intact.

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And I'm going to run the docker build command to create and

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to build the Docker image for the worker.

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And we'll just wait for that to finish.

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Once that is finished, when we run the docker images command,

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we are able to see all the images that are available and

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our newly created worker-app image.

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We will now run an instance of the worker-app.

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Now, the worker-app needs two links.

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1 is to the redis and another link to the postgres database.

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[No audio]

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Okay, so as soon as it runs, you can see that it's processed one vote.

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So that is the vote that we casted earlier.

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Okay. So now when I run docker ps command, I can see that there

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are four Containers running.

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So we have the worker-app ready.

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The next step is to build and deploy the result-app.

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So that's the last step.

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So we will create an image for the result-app.

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We will deploy it and link it to the Postgres database.

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So we go into the code repository for result.

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And I have all the application and Dockerfiles there.

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I will make sure the Dockerfile is intact.

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And then I'm going to run the docker build command to create

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an image for this result-app, and I will tag it results-app.

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It goes through all the Node.js related installation steps,

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and finally it's completed.

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So now I have a new image, which is the result-app.

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I'm now going to run the result-app, but since it is a web

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server, it has a Port requirement.

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So it exposes Port 80, and that's where it listens, I'm going

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to map Port 80 to Port 5001 because Port 5,000 on my local

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host is already occupied by the voting-app.

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So my result-app, I'd like to see it on Port 5001, so I'll

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map, I'll publish the Port 80 to 5001, and I also need to

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add a link because the result-app is linked to the db.

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So I'll add a link for that.

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Okay, so that should be it.

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And I'm now going to hit enter, and I can see that the application

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has started and it's connected to db, which is good.

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And if I go to the web browser and and establish a connectivity

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to Port 5001, and I can see the result page.

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So this is the result page.

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Since my vote was for cats, I see the 100% wards for CATS.

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I could also go back and change my vote.

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So if I go back and change my vote to DOGS, I see it's changed

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immediately. So every time I change my vote, it goes through the full cycle.

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The data goes through Redis, the worker processes it, updates

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the database, and then it's finally shown in this result

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page. So that's it for this demo, we took a look at the example-voting-app.

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We understood the architecture of it, how it works, and we

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also successfully deployed it with docker run commands using links.

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Thank you very much for your time.

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And in the next demo, we'll look at how to do the same with Docker Compose.

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[Outro music]