111 lines
4.5 KiB
Markdown
111 lines
4.5 KiB
Markdown
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For the rest of this tutorial, we will be working with a simple todo
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list manager that is running in Node.js. If you're not familiar with Node.js,
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don't worry! No real JavaScript experience is needed!
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At this point, your development team is quite small and you're simply
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building an app to prove out your MVP (minimum viable product). You want
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to show how it works and what it's capable of doing without needing to
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think about how it will work for a large team, multiple developers, etc.
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{: style="width:50%;" }
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{ .text-center }
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## Getting our App
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Before we can run the application, we need to get the application source code onto
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our machine. For real projects, you will typically clone the repo. But, for this tutorial,
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we have created a ZIP file containing the application.
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1. [Download the ZIP](/assets/app.zip). Open the ZIP file and make sure you extract the
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contents.
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1. Once extracted, use your favorite code editor to open the project. If you're in need of
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an editor, you can use [Visual Studio Code](https://code.visualstudio.com/). You should
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see the `package.json` and two subdirectories (`src` and `spec`).
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{: style="width:650px;margin-top:20px;"}
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{: .text-center }
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## Building the App's Container Image
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In order to build the application, we need to use a `Dockerfile`. A
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Dockerfile is simply a text-based script of instructions that is used to
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create a container image. If you've created Dockerfiles before, you might
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see a few flaws in the Dockerfile below. But, don't worry! We'll go over them.
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1. Create a file named Dockerfile with the following contents.
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```dockerfile
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FROM node:12-alpine
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WORKDIR /app
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COPY . .
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RUN yarn install --production
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CMD ["node", "/app/src/index.js"]
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```
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1. Build the container image using the `docker build` command.
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```bash
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docker build -t getting-started .
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```
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This command used the Dockerfile to build a new container image. You might
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have noticed that a lot of "layers" were downloaded. This is because we instructed
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the builder that we wanted to start from the `node:12-alpine` image. But, since we
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didn't have that on our machine, that image needed to be downloaded.
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After the image was downloaded, we copied in our application and used `yarn` to
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install our application's dependencies. The `CMD` directive specifies the default
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command to run when starting a container from this image.
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Finally, the `-t` flag tags our image. Think of this simply as a human-readable name
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for the final image. Since we named the image `getting-started`, we can refer to that
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image when we run a container.
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## Starting an App Container
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Now that we have an image, let's run the application! To do so, we will use the `docker run`
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command (remember that from earlier?).
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1. Start your container using the `docker run` command and specify the name of the image we
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just created:
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```bash
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docker run -dp 3000:3000 getting-started
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```
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Remember the `-d` and `-p` flags? We're running the new container in "detached" mode (in the
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background) and creating a mapping between the host's port 3000 to the container's port 3000.
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Without the port mapping, we wouldn't be able to access the application.
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1. After a few seconds, open your web browser to [http://localhost:3000](http://localhost:3000).
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You should see our app!
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{: style="width:450px;margin-top:20px;"}
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{: .text-center }
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1. Go ahead and add an item or two and see that it works as you expect. You can mark items as
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complete and remove items. Your frontend is successfully storing items in the backend!
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Pretty quick and easy, huh?
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At this point, you should have a running todo list manager with a few items, all built by you!
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Now, let's make a few changes and learn about managing our containers.
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If you take a quick look at the Docker Dashboard, you should see your two containers running now
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(this tutorial and your freshly launched app container)!
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## Recap
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In this short section, we learned the very basics about building a container image and created a
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Dockerfile to do so. Once we built an image, we started the container and saw the running app!
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Next, we're going to make a modification to our app and learn how to update our running application
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with a new image. Along the way, we'll learn a few other useful commands.
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